A-Level Chemistry: Nomenclature of Organic Compounds

hello everybody and welcome to this second video about organic chemistry for a level chemistry and in this video we&#39;re going to be looking at nomenclature which is all about how you name organic compounds and in this video we will be looking at the rules that there are for naming we&#39;ll be looking at how you name organic compounds when you&#39;ve been given a formula whether that&#39;s displayed formula structural or skeletal formula and last of all we&#39;ll look at how you draw structures when you have been given a name for an organic compound now what I should say is that I&#39;m going to be focusing on the functional groups and families of organic compounds that you&#39;re most likely to encounter in year one chemistry I will do another video for year two nomenclature and isomerism sometime in the near future organic compounds are named using the International Union of pure and applied chemistry system or I you pack for short to reassure you you don&#39;t need to remember what ru pact stands for you just need to be able to use the naming rules that I&#39;m going to outline now now the IBEW pack rules for naming chemicals can seem quite complicated so I&#39;m going to try and break down the structure that these names can have first of all all of the names have got a root now this root which is sometimes called an infix but normally it&#39;s called a root now this tells us about the length of the longest unbranched hydrocarbon chain present in a molecule and for simple molecules this will actually be how the name of the molecule begins now the good news is that the longest unbranched hydrocarbon chain that you&#39;re going to encounter is going to be six at a level chemistry whichever course it is that you&#39;re studying so you only need to learn the root word for these six and you will have come across these before hopefully at GCSE so you&#39;ll remember this and so if there is one it is Meath and two it is eath or earth and then it becomes probe Butte those are the four that don&#39;t kind of make sense so to speak you just have to remember those four and then after that it becomes like the number of sides of a particular shape so it becomes pent four five and hex four six so those are the root parts of the name Meath eath probe butte spent hex I recommend learning those as a matter of some importance now then we have got the particular ending now the ending for simple molecules will be either something like aim for if there are no double bonds or it might be in if there is a double bond present and so a simple molecule might have a name such as methane or ether in more complicated molecules might also have a suffix now suffix is a part of a word that goes at the end of a particular word and this suffix actually changes the name ending depending on what particular functional group might be present now an example of that is say an alcohol and the name ending will change to oh and last of all and this is not always the case that we have one of these in a molecule but that is a prefix now pre meaning before and so this will come in at the start and prefixes like I say you don&#39;t have prefixes for all molecules but this prefixes tells us about any branching that is in the organic compound but it also tells us about certain functional groups that might be sticking off the main carbon chain so let&#39;s just have a quick recap we will have a route part of the name which tells us how many carbon atoms there are in the longest unbranched carbon chain and then there&#39;ll be a typical ending which might be a m-- or it might be in and then there will occasionally be a suffix which will be where that n or n gets changed slightly if the functional group is more complicated and there will also sometimes be a prefix indicating branching or additional functional groups aside from the main one I think the best way to learn the main picture in greatest depth is actually through exposure to a variety of different organic compounds and so what I&#39;m going to do is I&#39;m going to work through the organic compounds that you&#39;re going to encounter in year one chemistry I&#39;ll start with the ones that you&#39;ll encounter most frequently and I&#39;ll build up into other ones that become more complicated and I&#39;ll introduce some of the IU pack rules as we go on through so let&#39;s start with alkanes which are the family of chemicals that you will have encountered at GCSE and they all have got the name that ends in the suffix pain now alkanes are quite straightforward so we won&#39;t spend long here let&#39;s just explore here we&#39;ve got one carbon and therefore the root for this word is going to be Meath and so since we have got one carbon and it is an alkane the name will be just simply methane we always run the route and the name ending together now for this one we&#39;ve got one two three carbon atoms in our longest chain and therefore the root is probe and since it is an alkane we just call it propane propane moving on to look at alkenes now we&#39;ll start with a few simple Keane&#39;s what these all have in common is the name ending een so if we have a look at these four alkenes first of all we&#39;ve got the one here top left where we have got two carbon atoms and so this will have the root eath and because it&#39;s an alkene we call it ething this second one here top right this one has obviously got three carbons and so because it&#39;s got three carbons it gets the root probe and so it becomes propane now alkenes are a little bit more complicated than alkanes because what about these two here at the bottom so we&#39;ve got this bottom left which has got four carbons which therefore means it gets the root butte and then this bottom right one has also got four carbons and it also therefore must have the prefix bewbs so we&#39;ve got two alkenes that are called butte and they do both get called butene however the root and the suffix are separated this time by a number and this number indicates the position of that double bond and what we do here is we number the carbon atoms we start at one end of the chain and we number them all one two three four and so this alkene the double bond is considered to be on position number one it&#39;s between the first and the second carbon so we say that the alkyne is attached to the first carbon because one of the i upat rules is that we keep our numbers as small as possible and so this alkyne is called butte 1 een what we&#39;ve got in the second alkene that looks like it should be called the same thing is we&#39;ve got our double bond between the second and the third carbon in the chain and so because it&#39;s between the second and the third carbon and because we have got the rule that we must keep the numbers as small as possible we call this Butte - in just a quick word about numbering you can number from whichever end of the chain gives you the smallest numbers it is not a case of always numbering from left to right or right to left the rules are quite strict on which functional groups always should have the lowest number but if you&#39;ve got something simple like an alkene the rule states that the number must always be as small as it could possibly be so for instance the Butte one in could alternatively if you&#39;d numbered from the right moving to the left you could argue that it is on the 3rd or between the 3rd and the 4th carbon atom and so it could be called Butte 3n but because the rule says that we keep the numbers as small as possible we were right to number them in the direction that we did at first and beat one een has got the smaller number let&#39;s take a look at some more complicated organic compounds these are going to have alkyl groups acting as branches so what that means is you&#39;ve got the main part of a carbon chain and then you&#39;ve got another carbon chain sticking out part way along and so an alkyl group is often represented as an R where that means we&#39;ve got a carbon chain of any length and the branch is considered to be any carbon chain that is moving off the main longest carbon chain and so the rules for naming these carbon chains are dependent once again on the number of carbon atoms in the R group and so the R group lengths I think you&#39;re going to be limited to one two or three but I&#39;ll include four in there as well and so they have the same naming format as the root part of the main part of an organic compound but the end of it changes slightly so an alkyl group of only one carbon is called a methyl group if there are two carbons in the chain is referred to as an ethyl group three carbons would be called a profile group four carbons would be a butyl group so if we take a look now at these three examples the first thing that we must always do when trying to name an organic compound is finding out what the longest part of the chain is now in this one we&#39;ve got two choices here we&#39;ve got this group which is a chain of three alternatively we&#39;ve got this group on here which actually is also a chain of three and so let&#39;s stick with our green bit as being our longest carbon chain and so what we&#39;ve got part way along is we&#39;ve got one two three carbons in our chain so the roots is going to be probe there are no double bonds so it&#39;s going to be propane but what we&#39;ve got this time is we&#39;ve got an extra carbon sticking out part way along the chain there is only one carbon in this alkyl group and so we call it methyl propane and successive words are actually merged together so methyl propane is actually technically only one word finally as part of this name we sometimes need to indicate the position of the alkyl group now for us the alkyl group is on the second carbon whichever end you start counting from and so this could be called two methyl propane and that two would be separated from the methyl propane by a hyphen however on this occasion this is not necessary because the methyl group could not be on position number one or three with the molecule still retaining the name propane because if it was on position number one the carbon chain would be extending down here and it wouldn&#39;t in fact be propane anymore it would be butane and so as such the name if this was an exam and this was the mark scheme the number would probably be in brackets implying that it&#39;s non-essential for naming of this compound if we move on to the one at the bottom here we need to find the longest carbon chain so the longest carbon chain could be like that which would be a chain of five alternatively it could start at the end and then bend down towards the bottom as I&#39;ve shown here in the yellow but this would also be a chain of five so it doesn&#39;t really matter whether you consider the horizontal green or the yellow that turns a corner it doesn&#39;t make any difference to our naming I&#39;m going to consider the green highlighted region to be the main longest on branch chain so one two three four five I&#39;ve numbered my carbon atoms it&#39;s the same in either direction and so we&#39;ve got five carbons which means that is pent there are no double bonds so it is pentane we do now have an alkyl group sticking out this has got two carbon atoms in it which means it is efile so we&#39;ve got efile pentane the carbon atoms are in position number three and so this is three efile pentane and again actually if it was in position number two or position number one it wouldn&#39;t be pentane anymore and so arguably that three is not vital but it is helpful for a speedy assignment of structure last of all top right we have got a chain of one two three four five as we go along here or we&#39;ve got the chain one two three four five six chain of six as we go that way absolutely looks like we&#39;ve got a couple of atoms of hydrogen missing and because six is bigger than five of course we go one two three four five six we need to number these around the corner so to speak because that is the longest unbranched chain of carbon atoms now I chose to number from the left not because that&#39;s what I&#39;ve always been doing but actually because that&#39;s where my alkyne is and alkenes have got a higher priority for naming than our alkyl groups and so this is a chain of six so it is hex it is an alkene so it is in the alkene double bond is between the first and the second carbon atom so it becomes hex one een we&#39;ve got a methyl group sticking out of the fourth carbon and so this becomes four because it&#39;s on the fourth carbon me file hex one I&#39;m not forgetting that we need hyphens to separate a number from letters and we have that for the prefix we also have it to separate the root from the suffix when there&#39;s some variety about where that functional group might be in a molecule let&#39;s take a look now at situations where there are two or even more al-qaeda branches coming out of the longest main carbon chain so let&#39;s work through these four you can pause it and have a go yourself if you feeling confident or you can work through them with me the first one we&#39;ve got here finding the longest carbon chain I think I&#39;ve drawn these reasonably straightforward and so we&#39;ve got a chain of five we could have that as well if we move to the middle and went down that&#39;s still a chain of five so that means that&#39;s not going to affect our numbering system so let&#39;s start our numbers one two three four five so we&#39;ve got those as our main chain so that&#39;s pent and that&#39;s an alkane because there&#39;s no double bond so it&#39;s going to end in pain this time though we&#39;ve got two branches we&#39;ve got a chain of one sticking out and a chain of two sticking out so we&#39;ve got an ethyl group that&#39;s what the chain of two is and then we&#39;ve got a methyl group as well the ethyl group is sticking out of position number three the methyl group position number two so when we run these two together to form part of the main name there is one extra rule the rule is the groups are named in increasing alphabetical order so efile begins with an e and that&#39;s closer to the beginning of the alphabet than a methyl group and so what that means is we&#39;re going to call this e file meth I&#39;ll pentane and because we&#39;ve got some elements of position the ethyl group is on position number three and so this is 3e Thyle 2 methyl pentane notice there the hyphens separating the numbers from the letter L and the letter M here and the number from the letter e so 3 me file to ethyl pentane if we move on to the next one we&#39;ve got a chain of 1 2 3 4 because that turns around the corner so this is going to be Butte it&#39;s an alkene so it is Butte M we&#39;re going to need to number our carbon atoms 1 2 3 4 and that means that our alkene is going to be called Butte 2 in because the double bond is between the second and the third carbon in the chain and then if we consider alkyl group sticking out of the side we&#39;ve got one here and we&#39;ve got a second one here so we&#39;ve got two groups that are in fact both methyl groups and this introduces an extra element to the naming if we&#39;ve got two of the same then we add the prefix die to the name of the alkyl group and so what this is going to be is this is going to be die me file butte to een but since the methyl groups could actually be in a variety of different positions we need to indicate with a 2 and followed by a comma and then a 3 the fact that these two methyl groups are on the second and third carbons if we move on to take a look at the compound that is bottom left looking for the longest carbon chain one two three four five that&#39;s a chain of five which you can&#39;t get if you move around in any bendings up or down so that is a chain of five which gives us pent we&#39;ve got an alkene again and so we&#39;ve got one two three four five and so this might make you think it should be pent for 18 or pent 5n however we must use the numberings that gives us the lowest numbers overall for our functional group for the alkyne and so it&#39;s not numbering left to right it&#39;s numbering right to left and so this gives us the name pent 1 een clearly that can&#39;t be the end of it though because we&#39;ve got these different alkyl group sticking out of the side we&#39;ve got a methyl group and a methyl group and a methyl group and a methyl group in fact they&#39;re not different they&#39;re all the same we&#39;ve got four methyl groups and so we need to acknowledge that by calling this methyl pent 1m but it&#39;s not just me file or dimethyl or even try me that this is tetra me file tetra meaning four and so if we&#39;ve got three of the same it would be called try four of the same is tetra and so we&#39;ve got four methyl groups sticking out of our pent 1n in various positions what are the positions well we&#39;ve got two of them on the third carbon atom in the chain and we&#39;ve got another two on the fourth and so this becomes three three four four tetra me file pent 1m and in a similar way to the alphabetical order we need to start at the smallest numbers for the positions of the branchings so it&#39;s three three four four tetra methyl pent one een as opposed to 4 4 3 3 or any random jumbling we start with the smaller numbers first now if we have a look at the group bottom right we&#39;ve got one two three four five six that&#39;s the chain of six I think that&#39;s the smallest chain that we&#39;ve got we&#39;ve got another chain of six if you start at the top and go down and then right but I&#39;m just going to keep it with our horizontal ones for now and so it&#39;s the chain of six so it&#39;s going to be hex there are no double bonds so it&#39;s in fact nice and easily going to be hexane this time let&#39;s have a look at our groups we&#39;ve got a methyl group here and a methyl group here and then we&#39;ve got an ethyl group in the middle and so II file me file and me file so in terms of numbering we&#39;ve got one two three four five six that gives us the numbers 2 5 &amp; 4 alternatively we could number from the other end and that gives us a 2 a 3 a 5 as our branching number so we&#39;ve either got 2 3 5 or 2 4 5 ok so the green numbers are the ones to go with because that gives us the smallest numbers overall for the carbon chains and there&#39;s no double bond to consider so it&#39;s going to be dimethyl because there are two methyl groups and there&#39;s only one e-file in terms of alphabetical order we don&#39;t consider the die tri or tetra in the alphabetical order we&#39;d only consider the e for the ethyl and the M for the methyl so even though Dee&#39;s before E this is going to be e Thyle die me file hexane we do need to consider the numbers the methyl groups are on position number 2 and position number 5 so this is going to be 2 comma 5 and then hyphens again and the ethyl group is on position number 3 so this is 3 e-file 2 5 dimethyl hexane let&#39;s move on now have a look at the hallo Geno alkane family hallo Geno alkanes have got the functional group are X where X is a halogen that is covalently bonded to a carbon chain now halogens group seven this is have obviously all got different names and so when it comes to naming them as part of an organic compound the prefix that we use must also change as well and so bromine as a halogen will have the prefix bromo chlorine has got the prefix chloro fluorine has got the prefix fluoro and iodine has got the prefix io doe and so the halogen is never considered to be part of the main functional group the halogen is always considered to be a prefix and just remind you from the previous page if there&#39;s more than one of the same halogen we&#39;re going to use the extra phrase die or tri or tetra depending on how many there are if we look at these four different halogen no alkanes starting with the one on the top left we have one carbon atom so this is going to be Meath there are no double bonds so it should be methane what there is are these four chlorines so this is going to be tetra chloro methane no need for any numbers because those four chlorines could not be in any other position if we move on to the second one we&#39;ve got a chain of two so we&#39;ve got two carbon atoms so this is going to be ethane again no double bonds we&#39;ve got two chlorines this time so this is going to be dye chloro we have got carbon number one and carbon number two so this is going to be 1 comma 2 - dye chloro ethane and dichloroethane remember is all one word if we move on to our third example we&#39;ve got a chain of four so it&#39;s going to be butane no double bonds so due to a m-- we have got one two three four or alternatively one two three four obviously the green if we use them for our local SAP positioning we&#39;re going to end up with smaller numbers so this is going to be bromine on position number one so this is one bromo chlorine is on position number two so 2-chloro butane on there this bottom example is slightly different or at least it introduces an extra level of complication because what we&#39;ve got is we&#39;ve got our two options for how we number them one two three four from the left or one two three four from the right it&#39;s very clear that we&#39;ve got two fluorine groups so this is going to be dye fluoro and we&#39;ve got to iodine groups so this is going to be die ioad oh and it&#39;s also clear that we&#39;ve got butane because it&#39;s a chain of four what&#39;s not clear is which of these numberings do we use do we use one to die floor oh three four die I Oh doh or do we use the red numbers and the answer for this is we use the numbers that give highest precedence to the halogen that&#39;s further towards the front of the alphabet and so since F comes before I this is going to be died floor Oh as higher precedence and then die I owed o as second which means that we&#39;re going to number it in that sequence to so we&#39;re going to use our 1 to die floor oh and our three four died i odo and the reason this is an issue is if we&#39;d use the red numbers the total of all of our numbers would have been exactly the same we&#39;d have used one two three four once whichever sequence we use but as I say what&#39;s really important to remember is we need to give higher precedence to F before I this complicates it because there&#39;s no different functional group they&#39;re both halogens but F before I it&#39;s very rare that you can situation and frankly I suspect you wouldn&#39;t get something as ambiguous as that for a level chemistry let&#39;s have a look next at alcohols which have got the functional group Oh H attached to an alkyl group of some sort and they will always have the suffix of all as the name ending let&#39;s have a look at naming these alcohols that we&#39;ve got drawn here first of all top left we&#39;ve got one carbon atom in this chain and so we&#39;ve got meth for that root and then in this instance it becomes methane because methane is very similar to methane but there&#39;s just an H group instead of one of the hydrogen&#39;s so we just in fact call this methanol with the one carbon giving us in fact on this occasion meth an if we have a look at the second one in the middle we&#39;ve got three carbon atoms in this chain and so this is going to be pro Pam and it&#39;s going to be all because we&#39;ve got the alcohol and similarly to our alkenes we need to give a position to the O eight group on this occasion because the O H group for the alcohol could be on the end or it could be in the middle and so on this occasion the alcohol group is in the middle on carbon atom number two if you have a look one two three it&#39;s on carbon number two if we start numbering on the top right we&#39;ll start numbering from the right-hand side one two three and so this is also going to be propanol but we need a different locals we need the number one for it to be pro pan one all having a look at the one on the bottom we&#39;ve got the chain of four and we&#39;ve got this o H group so this is going to be butanol Butte an for the root and we&#39;ve also got on this occasion we&#39;ve got a meth file group sticking out on here and so we&#39;ve got two different options we could have one two three four or we could have one two three four and on this occasion the yellow numbering system is going to win and the green won&#39;t be used and the reason for this is we always give the functional group the lowest number that we can if there is an option and so on this occasion this is going to be butan to i&#39;ll because the alcohol is located on the second carbon and so the methyl group this is going to be methyl butene to all the methyl group is located on carbon atom number three so this would be three methyl butan to all next we&#39;re going to take a look at aldehydes and ketones I&#39;m going to consider these two together because they&#39;re both quite similar and actually their naming conventions are very very simple there&#39;s not that much variety to the types of questions that you could be asked let&#39;s take a look at aldehydes first which have got the functional group C double bond o with a hydrogen attached to the same carbon with the oxygen doubly bonded to the carbon and then we&#39;ve got our for some alkyl group that could be really really long or it could even just be hydrogen so in our first example we&#39;ve got a carbon chain of two and then we&#39;ve got the aldehyde functional group at the end so we&#39;ve got F an as our root for two carbon atoms and then the name ending for aldehydes very easy just ends in L for aldehyde if we take a look at the bottom one we&#39;ve got a chain of four so this will be butan and then again al so butan is four four al is for aldehyde this time we have got a methyl group on position number two we always number from the aldehyde n first one two three four and so this is going to be to me file buta now if we take a look at ketones now which are it&#39;s very similar to aldehydes they&#39;ve still got that C double bond o group but this time it&#39;s in the middle of a chain so we&#39;ve got alkyl group growing one way but an alkyl group going the other way and on this occasion they cannot be hydrogen atoms if one of these was a hydrogen atom this would be an aldehyde and so the smallest ketone that we can actually have is the first one that we&#39;ve got here which is three carbon atoms in a chain with the double bond oxygen in the middle so this is pro Pam because we&#39;ve got three carbon atoms in the chain and ketones just have a name ending own so propane for three own propanone no number needed because if that double bond was not in the middle it wouldn&#39;t be a ketone anymore it would be an aldehyde broken out for the bottom one we&#39;ve got five carbon atoms in a chain so this is pent an for five the ketone takes higher priority over the methyl group that we&#39;ve gotten because you&#39;ll notice we&#39;ve got a methyl group here so we number from the end closest to the ketone one two three four five so this becomes pent an to own in the same way as alcohols and alkenes so this is Penton to own but of course we&#39;ve got that methyl group so this is for me file pent an to own let&#39;s take a look now at carboxylic acids which are characterized as having the functional group C double bond o H with an alkyl group attached here although that could be a hydrogen now the suffix used for carboxylic acids is always the same and it is always a weak acid which seems funny but the name ending is always nice and predictable and in fact I think carboxylic acids might even be the easiest to name so here we&#39;ve got a chain of 1 and so that is going to be methane as the root and then we just add the suffix on at the end and it becomes methanoic acid methane for the root of one and a weak acid moving on to the second one we have a chain of two so this becomes a fan for two then a weak acid for the carboxylic acid at the bottom we&#39;ve got a chain of three so prou pan is our root and our end is going to be a weak acid on here I say carboxylic acids are the easiest that&#39;s because the functional group has to be on the end in a similar way to aldehyde so there&#39;s never any position no lo container what we do need on this occasion at the bottom though is we do need a location for our chlorine group so the functional group always gets given position number one which means that the chlorine is put into position number two so this becomes two chloro propanoic acid and the chloro propanoic acid technically all on word so that was the end of carboxylic acids there really was that little to it moving on to a means that are about as difficult really and the amines are characterized as having the functional group NH 2 attached to a carbon chain of some sort and they&#39;re given the name ending a mean a very very logical suffix indeed so if we try and name these three molecules that are here we have got a chain of one so this is on this occasion referred to as a methyl group and so this is called me file a means and so that&#39;s probably the hardest part of naming a means is that the carbon chain the R group is almost named as if it was a branch to the aiming itself so the second one where we&#39;ve got two carbon atoms in this R group would be referred to as efile a mean the third one at the bottom little bit more complicated but not much we&#39;ve got a methyl group here and we&#39;ve got another methyl group here and so where we have got two methyl groups just like before we refer to this as dye me file and then this is still got the functional group of an and a mean even though there&#39;s an extra hydrogen that has been replaced so this is referred to as me file a mean the last functional group that you&#39;re likely to come across in year one a level chemistry is the nitrile family and the nitriles have got to the functional group where you&#39;ve got a carbon that is triply bonded to a nitrogen atom and then you&#39;ve got another carbon chain of any length and the suffix used here is very very logical just like before this is called nitrile that&#39;s the name ending of any nitrile if we take a look at how to name these nitriles just as before we look for the longest carbon chain that&#39;s on branched and we&#39;ve got three here so this is actually referred to as propane and then we&#39;ve got our nitrile functional group so this is just simply propane nitrile the second one we&#39;ve got a chain of two so this is ethane and again it&#39;s nitrile so it&#39;s ethane nitrile so at first glance the most difficult thing about nitriles is actually that their name is incredibly literal there is a propane attached to a nitrile or there is an ethane attached to a nitrile where it gets a little bit complicated is with branching but it still follows the same rules as before so we&#39;ve got a chain of four so this is butane nitrile and we&#39;ve got two different branches this time we&#39;ve got a methyl branch and we&#39;ve got an IO toe branch so they need to have locations the carbon here with the nitrile on it is position number one then that&#39;s position number two and then iodine&#39;s three and the other carbon is four it&#39;s really important to know that you do include the carbon that is attached to the nitrogen in terms of the numbering and so we always list these alphabetically and I comes before M in the alphabet so this is ioad o methyl butane nitrile the I odo group is on the third carbon and the methyl group is on the second so this is three i odo 2-methylbutane nitrile while nitriles are not that complicated to name it does give us an opportunity to discuss the separation of the root and the suffix and there is a slightly peculiar seeming rule at first which is that you can&#39;t have two consonants next to each other at the connection between the roots and the suffix so what you couldn&#39;t have is you couldn&#39;t have Boutin nitrile and so this becomes butane nitrile and that II will often be in bold on a mark scheme as a complete non negotiable and so as I say one of the ru pet naming conventions is you cannot have two consonants next to each other connecting the root and the suffix and similarly you couldn&#39;t have two vowels next to each other you would need to drop one of the vowels as you connect the suffix and the room together I&#39;ll give you an example of that in a minute a good platform to explore those extra naming conventions is to look at situations when there&#39;s more than one functional group when this is the case you need to look at what&#39;s called the order of precedence and so the group which has got the highest precedence or highest priority at sometimes called forms the suffix in other words the name ending all the others are considered then to be as kind of branches they&#39;re sticking out from the main molecule and they get given prefixes let&#39;s take a look at these six functional groups you are most likely to encounter in year one chemistry in their precedence order and so first of all the thing that takes greatest precedence over any of the others is the carboxylic acid functional group which means that there is almost no chance that this will be considered to be anything other than the main functional group and so usually you&#39;re going to use the suffix which is a weak acid a prefix does exist for it but I&#39;m going to put it in brackets because I can&#39;t consider this very likely that it will come up but the prefix would be carboxy if that carboxylic acid group was considered to be a branch ii on the precedence list is the night trials and this is a good opportunity to recap all the suffixes the nitriles ends in nitrile for its name and in fact if we just have a recap of the suffixes aldehydes is next on the priorities and that&#39;s got al as its suffix ketone is next and that pens in own then we&#39;ve got the alcohols which is all and a means which is a mean as its suffix the prefix for the nitrile it&#39;s quite unlikely that you&#39;re going to use this one as well I suspect and cyano is the prefix because nitrous does a lot of the same elements in it a cyanide aldehydes would be four-mile again putting that in brackets i think that&#39;s unlikely auch so for a ketone functional group has it considered to be a branch maybe not necessarily a branch but as a secondary functional group and then moving on to the ones that I think are far more likely are hydroxy for alcohol groups and you&#39;d probably use that in biology and another one that you definitely use in biology would be considering the a mean to be a secondary functional group of lower precedence and that would be considered to be an amino group and would use the amino prefix and just to remind you again that when you&#39;re numbering parts of a molecule you always give the lowest number to the functional group part and so the a mean would get the lowest number or the carboxylic acid would get the lowest number if there was one of them presence and so just as an example if we had an amine and a carboxylic acid here&#39;s our carboxylic acid I&#39;m gonna draw I&#39;m gonna make this ethanoic acid but there&#39;s going to be an amine group at end and so what you must always do is you must always look for the the group with the highest precedence and so the group with the highest precedence is this carboxylic acid group and so this is ethanoic acid there is this second functional group over here which is an amine but you can see the aiming is right down there in sixth position in the functional groups and so this is referred to as amino ethyle Noack acid no number needed here because the amino group could not be on that carbon because the carbon has already got four covalent bonds and there isn&#39;t space for the amino group to be on there so there&#39;s actually no numbering necessary for that amino group if we look now at a few more examples where there&#39;s more than one functional group in fact there&#39;s going to be two in every single one of these if we have a look at the top left we can see that we&#39;ve got our chain of three we can recognize that we have got two functional groups we&#39;ve got the nitrile functional group and we&#39;ve got the alcohol functional group of those the nitrile functional group takes precedence and so we&#39;ve got our chain of three and it&#39;s a nitrile so this is going to be propane nitrile but we&#39;ve got an alcohol group on position number two that&#39;s number one and that is position number two so this becomes two hydroxy propane nitrile top left we&#39;ve got a chain of four we&#39;ve got two functional groups again we&#39;ve got the amino functional group and we&#39;ve got the alcohol functional group on this occasion the alcohol takes precedence and so the amino is considered to be a branch as I&#39;ve said before you always aim to give the smaller number to the higher precedence functional group so on this occasion the alcohol is the higher precedence and so this becomes butan tuol as the higher precedence parts of the molecule then we&#39;ve got an amino group so this is amino butan so all we need to locate it and so the number that is given to locate it is the four four four amino butan two are looking bottom-left now we&#39;ve got our chain of two we&#39;ve got two functional groups again we&#39;ve got the aldehyde functional group and we&#39;ve got the amino functional group aldehyde takes precedence over the amino group so our chain of two makes it FM and it&#39;s an aldehyde so it&#39;s ethanal the amino group is the branch and the amino group is on position number two although arguably it couldn&#39;t be on position number one and still having it being an aldehyde so two amino ethyle out or just amino ethyle now if we have a look at the bottom right we can see that we&#39;ve got a double bond and we&#39;ve got the Oh H group of an alcohol now alkenes don&#39;t get given precedence in the same way as the others alkenes are often just woven into the name of the molecule but we&#39;ve got this which would be ethene and we&#39;ve got the other group that would be all for the alcohol and so we could be forgiven for naming this ething all but this is another example of the IU pack rules where you cannot have the root part of a name and the suffix both having a vowel one at its end and one at the beginning so we can&#39;t run these two vowels together so we drop the e from ethene and we run those together and it becomes ethanol so we&#39;ve lost that e and that&#39;s in the same way as the propane nitrile we couldn&#39;t have those two ends next to each other as propane nitrile it needs to be propane nitrile similar but the opposite way around we have to drop the e to make it to make sure that those two vowels aren&#39;t next to each other last of all in our naming rules exploration let&#39;s take a look at situations where organic compounds might have two of the same functional groups these are less likely to come up in year one chemistry probably they&#39;re likely to be year two chemistry instead but let&#39;s have a look at them now then we can always be ready for when it comes up in year two and so the three families that you&#39;re likely to come across our dials dines and dicarboxylic acids so if we take a look at the dials first it&#39;s very logical that this would be called a dial because there is not one alcohol group but there are two alcohol groups in this molecule we name them in the way that you might expect we&#39;ve got a carbon chain of two so this is going to be ethane and then we&#39;ve got the dials there on carbon number one and carbon number two so this becomes ethane one to dial notes again and though they&#39;re separated by some numbers so it&#39;s not really obvious that we&#39;ve got that E in there when you name alcohols normally it would be propanol or propane one all ethanol etc but dials need this e in there definitely needed definitely needed and the reason is that if it wasn&#39;t there and we ignore the numbers momentarily we&#39;d have the N and the D next to each other and these need to be separated with the letter e so we don&#39;t end up with two consonants next to each other in the naming convention now dying&#39;s in the same way they are recognizable by having not one double bond but two hence die-in when we name them we approach it in the same way we&#39;ve got a carbon chain of four so this would be butene but it&#39;s not butene it is beaut dying and how we name that so once again we can&#39;t have it as being beaut dying because that would give us at E and the D next to each other so this is going to be buta Dean more than that of course we need to have the numberings to give us our locations so our carbon atoms 1 2 3 4 this becomes buta 1 3 dying because the alkenes are located on the first and the third carbon atoms in the in they chain and so we need that a once again in the same way that we needed the e earlier on so dials always have that separating the root and the suffix and dying&#39;s always have the a separating the root and the suffix on here last of all if we take a look at carboxylic acids where there are two carboxylic acids in one molecule and so we&#39;ve got one at the end on the left and we&#39;ve got another one at the end on the right the longest carbon chain is a chain of three and so this would be pro Pam a weak acid but actually because there are two functional groups it becomes propane dye a weak acid on here so we need the e because once again it would be an N and a D connected by the connected together and we can&#39;t have that we need the e to separate to the two consonants and this dioic acid because there are two carboxylic acid groups so propane dioic acid and once again as I&#39;ve been saying before on an exam the e in there would be in bold because it is absolutely essential now we&#39;ve been doing a lot of naming of substances from their displayed formula keep in mind that you might be given structural formula or even skeletal formula for some of these substances so you might need to be able to name something that is a little bit more hidden about its structure what we&#39;re going to finish with in this video is doing its in the other direction being given the name for the substance and then giving a formula for it from that name I&#39;m going to be generous and I&#39;m going to make it so that I want you to give displayed formula you can always mix it up a little bit if you prefer to give a skeletal formula for speed I certainly think it&#39;s faster but you decide what you want to do so I&#39;m going to pop up some names you can pause it and see if you can try and draw those structures from those names okay so over to you with these hopefully if had a go at drawing those structures I&#39;ll just pop them all up all at once for all four of these okay here we go with the answers now for these four just be a little bit harsh with yourself if you&#39;ve been drawing some bonds that are a little it&#39;s sloppy I think mine are generally okay but it&#39;s really easy to kind of when you&#39;re drawing these to sort of miss and to have a carbon pointing kind of nowhere and a hydrogen not actually quite connected to it so really make sure your bonds connect the atoms that they&#39;re meant to be connecting on there and you have you haven&#39;t been sloppy so do be harsh with yourself at this point what you shouldn&#39;t be harsh with yourself about though is if you&#39;ve drawn these molecules the other way around so this H group could just as easily be up here in this position or this position provided its on carbon number one or alternatively what you could do is you could almost flip this whole molecule all the way around and so the O H group could be on this end and the bromine groups could be here and here in the same way the chlorine and the iodine have to be on position number one and then position number two for the iodine than chlorine but there&#39;s no reason why the iodine couldn&#39;t have been at this end and chlorine here okay provided the iodine is on an end and the chlorine is just next to it last of all let&#39;s just take a look at two complicated examples so it&#39;s got more than one functional group to them so again pause it try and name these I&#39;m just going to pop these answers up now both together and so the top left is butanoic acid is its main highest precedence carbon chain so there&#39;s a chain for butanoic acid there is an alcohol second functional group here connected to carbon not carbon number one - but it&#39;s on carbon number three so three hydroxy butanoic acid and the last of all bottom right we&#39;ve got a chain of four and it&#39;s a ketone so it&#39;s butanone with its normal naming no number needed but because we&#39;ve got a chloro group on this molecule we do need to call it butanone with a number so it becomes butan to own because it&#39;s carbon number one carbon number two because the highest precedence goes to the main functional group and then the chlorine becomes three chloro okay that&#39;s where I want to end this video thanks very much for listening I&#39;m going to follow this up with a video about isomerism later in the week so stay tuned for that I hope it&#39;s been useful bye-bye

hello everybody and welcome to this second video about organic chemistry for a level chemistry and in this video we&amp;#39;re going to be looking at nomenclature which is all about how you name organic compounds and in this video we will be looking at the rules that there are for naming we&amp;#39;ll be looking at how you name organic compounds when you&amp;#39;ve been given a formula whether that&amp;#39;s displayed formula structural or skeletal formula and last of all we&amp;#39;ll look at how you draw structures when you have been given a name for an organic compound now what I should say is that I&amp;#39;m going to be focusing on the functional groups and families of organic compounds that you&amp;#39;re most likely to encounter in year one chemistry I will do another video for year two nomenclature and isomerism sometime in the near future organic compounds are named using the International Union of pure and applied chemistry system or I you pack for short to reassure you you don&amp;#39;t need to remember what ru pact stands for you just need to be able to use the naming rules that I&amp;#39;m going to outline now now the IBEW pack rules for naming chemicals can seem quite complicated so I&amp;#39;m going to try and break down the structure that these names can have first of all all of the names have got a root now this root which is sometimes called an infix but normally it&amp;#39;s called a root now this tells us about the length of the longest unbranched hydrocarbon chain present in a molecule and for simple molecules this will actually be how the name of the molecule begins now the good news is that the longest unbranched hydrocarbon chain that you&amp;#39;re going to encounter is going to be six at a level chemistry whichever course it is that you&amp;#39;re studying so you only need to learn the root word for these six and you will have come across these before hopefully at GCSE so you&amp;#39;ll remember this and so if there is one it is Meath and two it is eath or earth and then it becomes probe Butte those are the four that don&amp;#39;t kind of make sense so to speak you just have to remember those four and then after that it becomes like the number of sides of a particular shape so it becomes pent four five and hex four six so those are the root parts of the name Meath eath probe butte spent hex I recommend learning those as a matter of some importance now then we have got the particular ending now the ending for simple molecules will be either something like aim for if there are no double bonds or it might be in if there is a double bond present and so a simple molecule might have a name such as methane or ether in more complicated molecules might also have a suffix now suffix is a part of a word that goes at the end of a particular word and this suffix actually changes the name ending depending on what particular functional group might be present now an example of that is say an alcohol and the name ending will change to oh and last of all and this is not always the case that we have one of these in a molecule but that is a prefix now pre meaning before and so this will come in at the start and prefixes like I say you don&amp;#39;t have prefixes for all molecules but this prefixes tells us about any branching that is in the organic compound but it also tells us about certain functional groups that might be sticking off the main carbon chain so let&amp;#39;s just have a quick recap we will have a route part of the name which tells us how many carbon atoms there are in the longest unbranched carbon chain and then there&amp;#39;ll be a typical ending which might be a m-- or it might be in and then there will occasionally be a suffix which will be where that n or n gets changed slightly if the functional group is more complicated and there will also sometimes be a prefix indicating branching or additional functional groups aside from the main one I think the best way to learn the main picture in greatest depth is actually through exposure to a variety of different organic compounds and so what I&amp;#39;m going to do is I&amp;#39;m going to work through the organic compounds that you&amp;#39;re going to encounter in year one chemistry I&amp;#39;ll start with the ones that you&amp;#39;ll encounter most frequently and I&amp;#39;ll build up into other ones that become more complicated and I&amp;#39;ll introduce some of the IU pack rules as we go on through so let&amp;#39;s start with alkanes which are the family of chemicals that you will have encountered at GCSE and they all have got the name that ends in the suffix pain now alkanes are quite straightforward so we won&amp;#39;t spend long here let&amp;#39;s just explore here we&amp;#39;ve got one carbon and therefore the root for this word is going to be Meath and so since we have got one carbon and it is an alkane the name will be just simply methane we always run the route and the name ending together now for this one we&amp;#39;ve got one two three carbon atoms in our longest chain and therefore the root is probe and since it is an alkane we just call it propane propane moving on to look at alkenes now we&amp;#39;ll start with a few simple Keane&amp;#39;s what these all have in common is the name ending een so if we have a look at these four alkenes first of all we&amp;#39;ve got the one here top left where we have got two carbon atoms and so this will have the root eath and because it&amp;#39;s an alkene we call it ething this second one here top right this one has obviously got three carbons and so because it&amp;#39;s got three carbons it gets the root probe and so it becomes propane now alkenes are a little bit more complicated than alkanes because what about these two here at the bottom so we&amp;#39;ve got this bottom left which has got four carbons which therefore means it gets the root butte and then this bottom right one has also got four carbons and it also therefore must have the prefix bewbs so we&amp;#39;ve got two alkenes that are called butte and they do both get called butene however the root and the suffix are separated this time by a number and this number indicates the position of that double bond and what we do here is we number the carbon atoms we start at one end of the chain and we number them all one two three four and so this alkene the double bond is considered to be on position number one it&amp;#39;s between the first and the second carbon so we say that the alkyne is attached to the first carbon because one of the i upat rules is that we keep our numbers as small as possible and so this alkyne is called butte 1 een what we&amp;#39;ve got in the second alkene that looks like it should be called the same thing is we&amp;#39;ve got our double bond between the second and the third carbon in the chain and so because it&amp;#39;s between the second and the third carbon and because we have got the rule that we must keep the numbers as small as possible we call this Butte - in just a quick word about numbering you can number from whichever end of the chain gives you the smallest numbers it is not a case of always numbering from left to right or right to left the rules are quite strict on which functional groups always should have the lowest number but if you&amp;#39;ve got something simple like an alkene the rule states that the number must always be as small as it could possibly be so for instance the Butte one in could alternatively if you&amp;#39;d numbered from the right moving to the left you could argue that it is on the 3rd or between the 3rd and the 4th carbon atom and so it could be called Butte 3n but because the rule says that we keep the numbers as small as possible we were right to number them in the direction that we did at first and beat one een has got the smaller number let&amp;#39;s take a look at some more complicated organic compounds these are going to have alkyl groups acting as branches so what that means is you&amp;#39;ve got the main part of a carbon chain and then you&amp;#39;ve got another carbon chain sticking out part way along and so an alkyl group is often represented as an R where that means we&amp;#39;ve got a carbon chain of any length and the branch is considered to be any carbon chain that is moving off the main longest carbon chain and so the rules for naming these carbon chains are dependent once again on the number of carbon atoms in the R group and so the R group lengths I think you&amp;#39;re going to be limited to one two or three but I&amp;#39;ll include four in there as well and so they have the same naming format as the root part of the main part of an organic compound but the end of it changes slightly so an alkyl group of only one carbon is called a methyl group if there are two carbons in the chain is referred to as an ethyl group three carbons would be called a profile group four carbons would be a butyl group so if we take a look now at these three examples the first thing that we must always do when trying to name an organic compound is finding out what the longest part of the chain is now in this one we&amp;#39;ve got two choices here we&amp;#39;ve got this group which is a chain of three alternatively we&amp;#39;ve got this group on here which actually is also a chain of three and so let&amp;#39;s stick with our green bit as being our longest carbon chain and so what we&amp;#39;ve got part way along is we&amp;#39;ve got one two three carbons in our chain so the roots is going to be probe there are no double bonds so it&amp;#39;s going to be propane but what we&amp;#39;ve got this time is we&amp;#39;ve got an extra carbon sticking out part way along the chain there is only one carbon in this alkyl group and so we call it methyl propane and successive words are actually merged together so methyl propane is actually technically only one word finally as part of this name we sometimes need to indicate the position of the alkyl group now for us the alkyl group is on the second carbon whichever end you start counting from and so this could be called two methyl propane and that two would be separated from the methyl propane by a hyphen however on this occasion this is not necessary because the methyl group could not be on position number one or three with the molecule still retaining the name propane because if it was on position number one the carbon chain would be extending down here and it wouldn&amp;#39;t in fact be propane anymore it would be butane and so as such the name if this was an exam and this was the mark scheme the number would probably be in brackets implying that it&amp;#39;s non-essential for naming of this compound if we move on to the one at the bottom here we need to find the longest carbon chain so the longest carbon chain could be like that which would be a chain of five alternatively it could start at the end and then bend down towards the bottom as I&amp;#39;ve shown here in the yellow but this would also be a chain of five so it doesn&amp;#39;t really matter whether you consider the horizontal green or the yellow that turns a corner it doesn&amp;#39;t make any difference to our naming I&amp;#39;m going to consider the green highlighted region to be the main longest on branch chain so one two three four five I&amp;#39;ve numbered my carbon atoms it&amp;#39;s the same in either direction and so we&amp;#39;ve got five carbons which means that is pent there are no double bonds so it is pentane we do now have an alkyl group sticking out this has got two carbon atoms in it which means it is efile so we&amp;#39;ve got efile pentane the carbon atoms are in position number three and so this is three efile pentane and again actually if it was in position number two or position number one it wouldn&amp;#39;t be pentane anymore and so arguably that three is not vital but it is helpful for a speedy assignment of structure last of all top right we have got a chain of one two three four five as we go along here or we&amp;#39;ve got the chain one two three four five six chain of six as we go that way absolutely looks like we&amp;#39;ve got a couple of atoms of hydrogen missing and because six is bigger than five of course we go one two three four five six we need to number these around the corner so to speak because that is the longest unbranched chain of carbon atoms now I chose to number from the left not because that&amp;#39;s what I&amp;#39;ve always been doing but actually because that&amp;#39;s where my alkyne is and alkenes have got a higher priority for naming than our alkyl groups and so this is a chain of six so it is hex it is an alkene so it is in the alkene double bond is between the first and the second carbon atom so it becomes hex one een we&amp;#39;ve got a methyl group sticking out of the fourth carbon and so this becomes four because it&amp;#39;s on the fourth carbon me file hex one I&amp;#39;m not forgetting that we need hyphens to separate a number from letters and we have that for the prefix we also have it to separate the root from the suffix when there&amp;#39;s some variety about where that functional group might be in a molecule let&amp;#39;s take a look now at situations where there are two or even more al-qaeda branches coming out of the longest main carbon chain so let&amp;#39;s work through these four you can pause it and have a go yourself if you feeling confident or you can work through them with me the first one we&amp;#39;ve got here finding the longest carbon chain I think I&amp;#39;ve drawn these reasonably straightforward and so we&amp;#39;ve got a chain of five we could have that as well if we move to the middle and went down that&amp;#39;s still a chain of five so that means that&amp;#39;s not going to affect our numbering system so let&amp;#39;s start our numbers one two three four five so we&amp;#39;ve got those as our main chain so that&amp;#39;s pent and that&amp;#39;s an alkane because there&amp;#39;s no double bond so it&amp;#39;s going to end in pain this time though we&amp;#39;ve got two branches we&amp;#39;ve got a chain of one sticking out and a chain of two sticking out so we&amp;#39;ve got an ethyl group that&amp;#39;s what the chain of two is and then we&amp;#39;ve got a methyl group as well the ethyl group is sticking out of position number three the methyl group position number two so when we run these two together to form part of the main name there is one extra rule the rule is the groups are named in increasing alphabetical order so efile begins with an e and that&amp;#39;s closer to the beginning of the alphabet than a methyl group and so what that means is we&amp;#39;re going to call this e file meth I&amp;#39;ll pentane and because we&amp;#39;ve got some elements of position the ethyl group is on position number three and so this is 3e Thyle 2 methyl pentane notice there the hyphens separating the numbers from the letter L and the letter M here and the number from the letter e so 3 me file to ethyl pentane if we move on to the next one we&amp;#39;ve got a chain of 1 2 3 4 because that turns around the corner so this is going to be Butte it&amp;#39;s an alkene so it is Butte M we&amp;#39;re going to need to number our carbon atoms 1 2 3 4 and that means that our alkene is going to be called Butte 2 in because the double bond is between the second and the third carbon in the chain and then if we consider alkyl group sticking out of the side we&amp;#39;ve got one here and we&amp;#39;ve got a second one here so we&amp;#39;ve got two groups that are in fact both methyl groups and this introduces an extra element to the naming if we&amp;#39;ve got two of the same then we add the prefix die to the name of the alkyl group and so what this is going to be is this is going to be die me file butte to een but since the methyl groups could actually be in a variety of different positions we need to indicate with a 2 and followed by a comma and then a 3 the fact that these two methyl groups are on the second and third carbons if we move on to take a look at the compound that is bottom left looking for the longest carbon chain one two three four five that&amp;#39;s a chain of five which you can&amp;#39;t get if you move around in any bendings up or down so that is a chain of five which gives us pent we&amp;#39;ve got an alkene again and so we&amp;#39;ve got one two three four five and so this might make you think it should be pent for 18 or pent 5n however we must use the numberings that gives us the lowest numbers overall for our functional group for the alkyne and so it&amp;#39;s not numbering left to right it&amp;#39;s numbering right to left and so this gives us the name pent 1 een clearly that can&amp;#39;t be the end of it though because we&amp;#39;ve got these different alkyl group sticking out of the side we&amp;#39;ve got a methyl group and a methyl group and a methyl group and a methyl group in fact they&amp;#39;re not different they&amp;#39;re all the same we&amp;#39;ve got four methyl groups and so we need to acknowledge that by calling this methyl pent 1m but it&amp;#39;s not just me file or dimethyl or even try me that this is tetra me file tetra meaning four and so if we&amp;#39;ve got three of the same it would be called try four of the same is tetra and so we&amp;#39;ve got four methyl groups sticking out of our pent 1n in various positions what are the positions well we&amp;#39;ve got two of them on the third carbon atom in the chain and we&amp;#39;ve got another two on the fourth and so this becomes three three four four tetra me file pent 1m and in a similar way to the alphabetical order we need to start at the smallest numbers for the positions of the branchings so it&amp;#39;s three three four four tetra methyl pent one een as opposed to 4 4 3 3 or any random jumbling we start with the smaller numbers first now if we have a look at the group bottom right we&amp;#39;ve got one two three four five six that&amp;#39;s the chain of six I think that&amp;#39;s the smallest chain that we&amp;#39;ve got we&amp;#39;ve got another chain of six if you start at the top and go down and then right but I&amp;#39;m just going to keep it with our horizontal ones for now and so it&amp;#39;s the chain of six so it&amp;#39;s going to be hex there are no double bonds so it&amp;#39;s in fact nice and easily going to be hexane this time let&amp;#39;s have a look at our groups we&amp;#39;ve got a methyl group here and a methyl group here and then we&amp;#39;ve got an ethyl group in the middle and so II file me file and me file so in terms of numbering we&amp;#39;ve got one two three four five six that gives us the numbers 2 5 &amp;amp; 4 alternatively we could number from the other end and that gives us a 2 a 3 a 5 as our branching number so we&amp;#39;ve either got 2 3 5 or 2 4 5 ok so the green numbers are the ones to go with because that gives us the smallest numbers overall for the carbon chains and there&amp;#39;s no double bond to consider so it&amp;#39;s going to be dimethyl because there are two methyl groups and there&amp;#39;s only one e-file in terms of alphabetical order we don&amp;#39;t consider the die tri or tetra in the alphabetical order we&amp;#39;d only consider the e for the ethyl and the M for the methyl so even though Dee&amp;#39;s before E this is going to be e Thyle die me file hexane we do need to consider the numbers the methyl groups are on position number 2 and position number 5 so this is going to be 2 comma 5 and then hyphens again and the ethyl group is on position number 3 so this is 3 e-file 2 5 dimethyl hexane let&amp;#39;s move on now have a look at the hallo Geno alkane family hallo Geno alkanes have got the functional group are X where X is a halogen that is covalently bonded to a carbon chain now halogens group seven this is have obviously all got different names and so when it comes to naming them as part of an organic compound the prefix that we use must also change as well and so bromine as a halogen will have the prefix bromo chlorine has got the prefix chloro fluorine has got the prefix fluoro and iodine has got the prefix io doe and so the halogen is never considered to be part of the main functional group the halogen is always considered to be a prefix and just remind you from the previous page if there&amp;#39;s more than one of the same halogen we&amp;#39;re going to use the extra phrase die or tri or tetra depending on how many there are if we look at these four different halogen no alkanes starting with the one on the top left we have one carbon atom so this is going to be Meath there are no double bonds so it should be methane what there is are these four chlorines so this is going to be tetra chloro methane no need for any numbers because those four chlorines could not be in any other position if we move on to the second one we&amp;#39;ve got a chain of two so we&amp;#39;ve got two carbon atoms so this is going to be ethane again no double bonds we&amp;#39;ve got two chlorines this time so this is going to be dye chloro we have got carbon number one and carbon number two so this is going to be 1 comma 2 - dye chloro ethane and dichloroethane remember is all one word if we move on to our third example we&amp;#39;ve got a chain of four so it&amp;#39;s going to be butane no double bonds so due to a m-- we have got one two three four or alternatively one two three four obviously the green if we use them for our local SAP positioning we&amp;#39;re going to end up with smaller numbers so this is going to be bromine on position number one so this is one bromo chlorine is on position number two so 2-chloro butane on there this bottom example is slightly different or at least it introduces an extra level of complication because what we&amp;#39;ve got is we&amp;#39;ve got our two options for how we number them one two three four from the left or one two three four from the right it&amp;#39;s very clear that we&amp;#39;ve got two fluorine groups so this is going to be dye fluoro and we&amp;#39;ve got to iodine groups so this is going to be die ioad oh and it&amp;#39;s also clear that we&amp;#39;ve got butane because it&amp;#39;s a chain of four what&amp;#39;s not clear is which of these numberings do we use do we use one to die floor oh three four die I Oh doh or do we use the red numbers and the answer for this is we use the numbers that give highest precedence to the halogen that&amp;#39;s further towards the front of the alphabet and so since F comes before I this is going to be died floor Oh as higher precedence and then die I owed o as second which means that we&amp;#39;re going to number it in that sequence to so we&amp;#39;re going to use our 1 to die floor oh and our three four died i odo and the reason this is an issue is if we&amp;#39;d use the red numbers the total of all of our numbers would have been exactly the same we&amp;#39;d have used one two three four once whichever sequence we use but as I say what&amp;#39;s really important to remember is we need to give higher precedence to F before I this complicates it because there&amp;#39;s no different functional group they&amp;#39;re both halogens but F before I it&amp;#39;s very rare that you can situation and frankly I suspect you wouldn&amp;#39;t get something as ambiguous as that for a level chemistry let&amp;#39;s have a look next at alcohols which have got the functional group Oh H attached to an alkyl group of some sort and they will always have the suffix of all as the name ending let&amp;#39;s have a look at naming these alcohols that we&amp;#39;ve got drawn here first of all top left we&amp;#39;ve got one carbon atom in this chain and so we&amp;#39;ve got meth for that root and then in this instance it becomes methane because methane is very similar to methane but there&amp;#39;s just an H group instead of one of the hydrogen&amp;#39;s so we just in fact call this methanol with the one carbon giving us in fact on this occasion meth an if we have a look at the second one in the middle we&amp;#39;ve got three carbon atoms in this chain and so this is going to be pro Pam and it&amp;#39;s going to be all because we&amp;#39;ve got the alcohol and similarly to our alkenes we need to give a position to the O eight group on this occasion because the O H group for the alcohol could be on the end or it could be in the middle and so on this occasion the alcohol group is in the middle on carbon atom number two if you have a look one two three it&amp;#39;s on carbon number two if we start numbering on the top right we&amp;#39;ll start numbering from the right-hand side one two three and so this is also going to be propanol but we need a different locals we need the number one for it to be pro pan one all having a look at the one on the bottom we&amp;#39;ve got the chain of four and we&amp;#39;ve got this o H group so this is going to be butanol Butte an for the root and we&amp;#39;ve also got on this occasion we&amp;#39;ve got a meth file group sticking out on here and so we&amp;#39;ve got two different options we could have one two three four or we could have one two three four and on this occasion the yellow numbering system is going to win and the green won&amp;#39;t be used and the reason for this is we always give the functional group the lowest number that we can if there is an option and so on this occasion this is going to be butan to i&amp;#39;ll because the alcohol is located on the second carbon and so the methyl group this is going to be methyl butene to all the methyl group is located on carbon atom number three so this would be three methyl butan to all next we&amp;#39;re going to take a look at aldehydes and ketones I&amp;#39;m going to consider these two together because they&amp;#39;re both quite similar and actually their naming conventions are very very simple there&amp;#39;s not that much variety to the types of questions that you could be asked let&amp;#39;s take a look at aldehydes first which have got the functional group C double bond o with a hydrogen attached to the same carbon with the oxygen doubly bonded to the carbon and then we&amp;#39;ve got our for some alkyl group that could be really really long or it could even just be hydrogen so in our first example we&amp;#39;ve got a carbon chain of two and then we&amp;#39;ve got the aldehyde functional group at the end so we&amp;#39;ve got F an as our root for two carbon atoms and then the name ending for aldehydes very easy just ends in L for aldehyde if we take a look at the bottom one we&amp;#39;ve got a chain of four so this will be butan and then again al so butan is four four al is for aldehyde this time we have got a methyl group on position number two we always number from the aldehyde n first one two three four and so this is going to be to me file buta now if we take a look at ketones now which are it&amp;#39;s very similar to aldehydes they&amp;#39;ve still got that C double bond o group but this time it&amp;#39;s in the middle of a chain so we&amp;#39;ve got alkyl group growing one way but an alkyl group going the other way and on this occasion they cannot be hydrogen atoms if one of these was a hydrogen atom this would be an aldehyde and so the smallest ketone that we can actually have is the first one that we&amp;#39;ve got here which is three carbon atoms in a chain with the double bond oxygen in the middle so this is pro Pam because we&amp;#39;ve got three carbon atoms in the chain and ketones just have a name ending own so propane for three own propanone no number needed because if that double bond was not in the middle it wouldn&amp;#39;t be a ketone anymore it would be an aldehyde broken out for the bottom one we&amp;#39;ve got five carbon atoms in a chain so this is pent an for five the ketone takes higher priority over the methyl group that we&amp;#39;ve gotten because you&amp;#39;ll notice we&amp;#39;ve got a methyl group here so we number from the end closest to the ketone one two three four five so this becomes pent an to own in the same way as alcohols and alkenes so this is Penton to own but of course we&amp;#39;ve got that methyl group so this is for me file pent an to own let&amp;#39;s take a look now at carboxylic acids which are characterized as having the functional group C double bond o H with an alkyl group attached here although that could be a hydrogen now the suffix used for carboxylic acids is always the same and it is always a weak acid which seems funny but the name ending is always nice and predictable and in fact I think carboxylic acids might even be the easiest to name so here we&amp;#39;ve got a chain of 1 and so that is going to be methane as the root and then we just add the suffix on at the end and it becomes methanoic acid methane for the root of one and a weak acid moving on to the second one we have a chain of two so this becomes a fan for two then a weak acid for the carboxylic acid at the bottom we&amp;#39;ve got a chain of three so prou pan is our root and our end is going to be a weak acid on here I say carboxylic acids are the easiest that&amp;#39;s because the functional group has to be on the end in a similar way to aldehyde so there&amp;#39;s never any position no lo container what we do need on this occasion at the bottom though is we do need a location for our chlorine group so the functional group always gets given position number one which means that the chlorine is put into position number two so this becomes two chloro propanoic acid and the chloro propanoic acid technically all on word so that was the end of carboxylic acids there really was that little to it moving on to a means that are about as difficult really and the amines are characterized as having the functional group NH 2 attached to a carbon chain of some sort and they&amp;#39;re given the name ending a mean a very very logical suffix indeed so if we try and name these three molecules that are here we have got a chain of one so this is on this occasion referred to as a methyl group and so this is called me file a means and so that&amp;#39;s probably the hardest part of naming a means is that the carbon chain the R group is almost named as if it was a branch to the aiming itself so the second one where we&amp;#39;ve got two carbon atoms in this R group would be referred to as efile a mean the third one at the bottom little bit more complicated but not much we&amp;#39;ve got a methyl group here and we&amp;#39;ve got another methyl group here and so where we have got two methyl groups just like before we refer to this as dye me file and then this is still got the functional group of an and a mean even though there&amp;#39;s an extra hydrogen that has been replaced so this is referred to as me file a mean the last functional group that you&amp;#39;re likely to come across in year one a level chemistry is the nitrile family and the nitriles have got to the functional group where you&amp;#39;ve got a carbon that is triply bonded to a nitrogen atom and then you&amp;#39;ve got another carbon chain of any length and the suffix used here is very very logical just like before this is called nitrile that&amp;#39;s the name ending of any nitrile if we take a look at how to name these nitriles just as before we look for the longest carbon chain that&amp;#39;s on branched and we&amp;#39;ve got three here so this is actually referred to as propane and then we&amp;#39;ve got our nitrile functional group so this is just simply propane nitrile the second one we&amp;#39;ve got a chain of two so this is ethane and again it&amp;#39;s nitrile so it&amp;#39;s ethane nitrile so at first glance the most difficult thing about nitriles is actually that their name is incredibly literal there is a propane attached to a nitrile or there is an ethane attached to a nitrile where it gets a little bit complicated is with branching but it still follows the same rules as before so we&amp;#39;ve got a chain of four so this is butane nitrile and we&amp;#39;ve got two different branches this time we&amp;#39;ve got a methyl branch and we&amp;#39;ve got an IO toe branch so they need to have locations the carbon here with the nitrile on it is position number one then that&amp;#39;s position number two and then iodine&amp;#39;s three and the other carbon is four it&amp;#39;s really important to know that you do include the carbon that is attached to the nitrogen in terms of the numbering and so we always list these alphabetically and I comes before M in the alphabet so this is ioad o methyl butane nitrile the I odo group is on the third carbon and the methyl group is on the second so this is three i odo 2-methylbutane nitrile while nitriles are not that complicated to name it does give us an opportunity to discuss the separation of the root and the suffix and there is a slightly peculiar seeming rule at first which is that you can&amp;#39;t have two consonants next to each other at the connection between the roots and the suffix so what you couldn&amp;#39;t have is you couldn&amp;#39;t have Boutin nitrile and so this becomes butane nitrile and that II will often be in bold on a mark scheme as a complete non negotiable and so as I say one of the ru pet naming conventions is you cannot have two consonants next to each other connecting the root and the suffix and similarly you couldn&amp;#39;t have two vowels next to each other you would need to drop one of the vowels as you connect the suffix and the room together I&amp;#39;ll give you an example of that in a minute a good platform to explore those extra naming conventions is to look at situations when there&amp;#39;s more than one functional group when this is the case you need to look at what&amp;#39;s called the order of precedence and so the group which has got the highest precedence or highest priority at sometimes called forms the suffix in other words the name ending all the others are considered then to be as kind of branches they&amp;#39;re sticking out from the main molecule and they get given prefixes let&amp;#39;s take a look at these six functional groups you are most likely to encounter in year one chemistry in their precedence order and so first of all the thing that takes greatest precedence over any of the others is the carboxylic acid functional group which means that there is almost no chance that this will be considered to be anything other than the main functional group and so usually you&amp;#39;re going to use the suffix which is a weak acid a prefix does exist for it but I&amp;#39;m going to put it in brackets because I can&amp;#39;t consider this very likely that it will come up but the prefix would be carboxy if that carboxylic acid group was considered to be a branch ii on the precedence list is the night trials and this is a good opportunity to recap all the suffixes the nitriles ends in nitrile for its name and in fact if we just have a recap of the suffixes aldehydes is next on the priorities and that&amp;#39;s got al as its suffix ketone is next and that pens in own then we&amp;#39;ve got the alcohols which is all and a means which is a mean as its suffix the prefix for the nitrile it&amp;#39;s quite unlikely that you&amp;#39;re going to use this one as well I suspect and cyano is the prefix because nitrous does a lot of the same elements in it a cyanide aldehydes would be four-mile again putting that in brackets i think that&amp;#39;s unlikely auch so for a ketone functional group has it considered to be a branch maybe not necessarily a branch but as a secondary functional group and then moving on to the ones that I think are far more likely are hydroxy for alcohol groups and you&amp;#39;d probably use that in biology and another one that you definitely use in biology would be considering the a mean to be a secondary functional group of lower precedence and that would be considered to be an amino group and would use the amino prefix and just to remind you again that when you&amp;#39;re numbering parts of a molecule you always give the lowest number to the functional group part and so the a mean would get the lowest number or the carboxylic acid would get the lowest number if there was one of them presence and so just as an example if we had an amine and a carboxylic acid here&amp;#39;s our carboxylic acid I&amp;#39;m gonna draw I&amp;#39;m gonna make this ethanoic acid but there&amp;#39;s going to be an amine group at end and so what you must always do is you must always look for the the group with the highest precedence and so the group with the highest precedence is this carboxylic acid group and so this is ethanoic acid there is this second functional group over here which is an amine but you can see the aiming is right down there in sixth position in the functional groups and so this is referred to as amino ethyle Noack acid no number needed here because the amino group could not be on that carbon because the carbon has already got four covalent bonds and there isn&amp;#39;t space for the amino group to be on there so there&amp;#39;s actually no numbering necessary for that amino group if we look now at a few more examples where there&amp;#39;s more than one functional group in fact there&amp;#39;s going to be two in every single one of these if we have a look at the top left we can see that we&amp;#39;ve got our chain of three we can recognize that we have got two functional groups we&amp;#39;ve got the nitrile functional group and we&amp;#39;ve got the alcohol functional group of those the nitrile functional group takes precedence and so we&amp;#39;ve got our chain of three and it&amp;#39;s a nitrile so this is going to be propane nitrile but we&amp;#39;ve got an alcohol group on position number two that&amp;#39;s number one and that is position number two so this becomes two hydroxy propane nitrile top left we&amp;#39;ve got a chain of four we&amp;#39;ve got two functional groups again we&amp;#39;ve got the amino functional group and we&amp;#39;ve got the alcohol functional group on this occasion the alcohol takes precedence and so the amino is considered to be a branch as I&amp;#39;ve said before you always aim to give the smaller number to the higher precedence functional group so on this occasion the alcohol is the higher precedence and so this becomes butan tuol as the higher precedence parts of the molecule then we&amp;#39;ve got an amino group so this is amino butan so all we need to locate it and so the number that is given to locate it is the four four four amino butan two are looking bottom-left now we&amp;#39;ve got our chain of two we&amp;#39;ve got two functional groups again we&amp;#39;ve got the aldehyde functional group and we&amp;#39;ve got the amino functional group aldehyde takes precedence over the amino group so our chain of two makes it FM and it&amp;#39;s an aldehyde so it&amp;#39;s ethanal the amino group is the branch and the amino group is on position number two although arguably it couldn&amp;#39;t be on position number one and still having it being an aldehyde so two amino ethyle out or just amino ethyle now if we have a look at the bottom right we can see that we&amp;#39;ve got a double bond and we&amp;#39;ve got the Oh H group of an alcohol now alkenes don&amp;#39;t get given precedence in the same way as the others alkenes are often just woven into the name of the molecule but we&amp;#39;ve got this which would be ethene and we&amp;#39;ve got the other group that would be all for the alcohol and so we could be forgiven for naming this ething all but this is another example of the IU pack rules where you cannot have the root part of a name and the suffix both having a vowel one at its end and one at the beginning so we can&amp;#39;t run these two vowels together so we drop the e from ethene and we run those together and it becomes ethanol so we&amp;#39;ve lost that e and that&amp;#39;s in the same way as the propane nitrile we couldn&amp;#39;t have those two ends next to each other as propane nitrile it needs to be propane nitrile similar but the opposite way around we have to drop the e to make it to make sure that those two vowels aren&amp;#39;t next to each other last of all in our naming rules exploration let&amp;#39;s take a look at situations where organic compounds might have two of the same functional groups these are less likely to come up in year one chemistry probably they&amp;#39;re likely to be year two chemistry instead but let&amp;#39;s have a look at them now then we can always be ready for when it comes up in year two and so the three families that you&amp;#39;re likely to come across our dials dines and dicarboxylic acids so if we take a look at the dials first it&amp;#39;s very logical that this would be called a dial because there is not one alcohol group but there are two alcohol groups in this molecule we name them in the way that you might expect we&amp;#39;ve got a carbon chain of two so this is going to be ethane and then we&amp;#39;ve got the dials there on carbon number one and carbon number two so this becomes ethane one to dial notes again and though they&amp;#39;re separated by some numbers so it&amp;#39;s not really obvious that we&amp;#39;ve got that E in there when you name alcohols normally it would be propanol or propane one all ethanol etc but dials need this e in there definitely needed definitely needed and the reason is that if it wasn&amp;#39;t there and we ignore the numbers momentarily we&amp;#39;d have the N and the D next to each other and these need to be separated with the letter e so we don&amp;#39;t end up with two consonants next to each other in the naming convention now dying&amp;#39;s in the same way they are recognizable by having not one double bond but two hence die-in when we name them we approach it in the same way we&amp;#39;ve got a carbon chain of four so this would be butene but it&amp;#39;s not butene it is beaut dying and how we name that so once again we can&amp;#39;t have it as being beaut dying because that would give us at E and the D next to each other so this is going to be buta Dean more than that of course we need to have the numberings to give us our locations so our carbon atoms 1 2 3 4 this becomes buta 1 3 dying because the alkenes are located on the first and the third carbon atoms in the in they chain and so we need that a once again in the same way that we needed the e earlier on so dials always have that separating the root and the suffix and dying&amp;#39;s always have the a separating the root and the suffix on here last of all if we take a look at carboxylic acids where there are two carboxylic acids in one molecule and so we&amp;#39;ve got one at the end on the left and we&amp;#39;ve got another one at the end on the right the longest carbon chain is a chain of three and so this would be pro Pam a weak acid but actually because there are two functional groups it becomes propane dye a weak acid on here so we need the e because once again it would be an N and a D connected by the connected together and we can&amp;#39;t have that we need the e to separate to the two consonants and this dioic acid because there are two carboxylic acid groups so propane dioic acid and once again as I&amp;#39;ve been saying before on an exam the e in there would be in bold because it is absolutely essential now we&amp;#39;ve been doing a lot of naming of substances from their displayed formula keep in mind that you might be given structural formula or even skeletal formula for some of these substances so you might need to be able to name something that is a little bit more hidden about its structure what we&amp;#39;re going to finish with in this video is doing its in the other direction being given the name for the substance and then giving a formula for it from that name I&amp;#39;m going to be generous and I&amp;#39;m going to make it so that I want you to give displayed formula you can always mix it up a little bit if you prefer to give a skeletal formula for speed I certainly think it&amp;#39;s faster but you decide what you want to do so I&amp;#39;m going to pop up some names you can pause it and see if you can try and draw those structures from those names okay so over to you with these hopefully if had a go at drawing those structures I&amp;#39;ll just pop them all up all at once for all four of these okay here we go with the answers now for these four just be a little bit harsh with yourself if you&amp;#39;ve been drawing some bonds that are a little it&amp;#39;s sloppy I think mine are generally okay but it&amp;#39;s really easy to kind of when you&amp;#39;re drawing these to sort of miss and to have a carbon pointing kind of nowhere and a hydrogen not actually quite connected to it so really make sure your bonds connect the atoms that they&amp;#39;re meant to be connecting on there and you have you haven&amp;#39;t been sloppy so do be harsh with yourself at this point what you shouldn&amp;#39;t be harsh with yourself about though is if you&amp;#39;ve drawn these molecules the other way around so this H group could just as easily be up here in this position or this position provided its on carbon number one or alternatively what you could do is you could almost flip this whole molecule all the way around and so the O H group could be on this end and the bromine groups could be here and here in the same way the chlorine and the iodine have to be on position number one and then position number two for the iodine than chlorine but there&amp;#39;s no reason why the iodine couldn&amp;#39;t have been at this end and chlorine here okay provided the iodine is on an end and the chlorine is just next to it last of all let&amp;#39;s just take a look at two complicated examples so it&amp;#39;s got more than one functional group to them so again pause it try and name these I&amp;#39;m just going to pop these answers up now both together and so the top left is butanoic acid is its main highest precedence carbon chain so there&amp;#39;s a chain for butanoic acid there is an alcohol second functional group here connected to carbon not carbon number one - but it&amp;#39;s on carbon number three so three hydroxy butanoic acid and the last of all bottom right we&amp;#39;ve got a chain of four and it&amp;#39;s a ketone so it&amp;#39;s butanone with its normal naming no number needed but because we&amp;#39;ve got a chloro group on this molecule we do need to call it butanone with a number so it becomes butan to own because it&amp;#39;s carbon number one carbon number two because the highest precedence goes to the main functional group and then the chlorine becomes three chloro okay that&amp;#39;s where I want to end this video thanks very much for listening I&amp;#39;m going to follow this up with a video about isomerism later in the week so stay tuned for that I hope it&amp;#39;s been useful bye-bye

Transcript for:A-Level Chemistry: Nomenclature of Organic Compounds

Transcript for:
A-Level Chemistry: Nomenclature of Organic Compounds