all right folks we are halfway through the hydrocarbons and now we're ready to learn about the alkenes or the double bond Daredevil okay so they're led by the charismatic propene patriarch and they're all about their double bonds and using them as concealed weapons to launch any kind of surprise attack against any other family it wants okay so it really does cause reactivity and those double bonds can break creating even more diversity in organic compounds all right folks the functions are of course numerous just like every other organic compound we saw we see them for detergents rubbers Plastics gasoline the main thing you want to understand is that you have something that's unsaturated so you have an unsaturated hydrocarbon with at least one carbon carbon double bond and of course double bonds are going to be SP2 hydroid okay now guess what folks when it comes to naming it's just like the alanes the only difference is the suffix so we always start with our prefix Our Roots and our suffix the suffix here is going to change instead of being ending in A and E like we saw before with the um alkanes now we're going to end in e NE e which is going to be the alenes okay folks so just keep that in mind another thing is you must put the location of the double bond in the actual name as well so when you're done with your actual root of it and you have your double bond so you have your root pin for example let's just do this we have five carbons we see the double bond here so some folks might say I want to start numbering carbon one 2 3 four and five making the double bond start at Carbon four remember the goal is that we want to have the lowest carbon chain so we actually would start here one 2 3 4 five okay and so I can put a location in front of this name since it's five carbons and put a one- pintin so the root kind of changes a little bit as well because you want to put the location there now same thing with buttine here we want to number it one two 3 four so we can have one- buttine instead of having three- buttin because we want to get the lowest number okay again just like the H alanes you also want to have the carbon chain um that is going to be numbered from the end into the double bond so that's just me explaining that a little bit more detail all right folks let's get some examples all right folks so we know the drill we got prefix root and suffix we know our suffix is going to end it's not going to be in and our root has to have a location attached to it everything else is pretty much the same so first thing first let's get our root let's go ahead and figure out exactly what our longest carbon chain is going to be so we can number it one two 3 four that's four carbons or we can have 1 2 3 four five carbons so this would be our longest parent chain here now how we number we number based on the double bond so we're going to be numbering here one 2 3 four and five so here's our longest parent chain we have five so we know we're going to be dealing with pint it's a double bond here so the ending is going to be in now what carbon does a double bond start carbon number one so we already have majority of our name ready all right folks next we got to consolidate any substituents so I see ch3 here which we know is going to be our methyl group what location is it on carbon 3 there's only one prefix so 3-methyl dash one Das pin te okay so again anytime you have a letter and a number you must have a dash in between let's do the next one here we got to make sure that we're getting our longest parent change so let's try to count that one first we can do one two three that's too short 1 2 3 4 five six seven that's pretty long okay so that's going to be the one we start with 1 2 3 4 5 6 7 all right this is our parent chain here now the question becomes how do we number it well whatever's closer to the double bond so we number it here 1 2 3 four the double bond starts at Carbon four we number it from this way one two three the double bond starts at Carbon 3 so that's what we want okay now what do we do after that of course I just want to get all of our substituents hydrogens are not considered substituent only of course our Al group okay the things that are attached with carbon so let me go ahead and look at that um and I have seven carbons so I know I'm going to have Hep this is a double bond here so it has to be heptin location of the start of the double bond is going to be three heptin I do have a prefix because I have a substituent here which is methyl it's on carbon number six so this is going to be 6-methyl Dash 3- heptin all right folks so as we discuss when a molecule has four or more carbon atoms isomers can form and we know that isomers are are compounds that share the same molecular formula but have different properties due to variations in the arrangement of atoms so among these are the stereo isomers and they have the same atomic connectivity but differ in the spatial arrangement of their groups now we talked about Optical isomers B enantiomers and of course structural isomer when it came to alkanes but in the context of alkenes we specifically focus on geometric isomers okay or Cy trans isomerate type of isomerism occurs because of the double bomb between two carbons and alken this is going to restrict the rotation around those atoms so for example unlike single bonds which you see here that allow free rotation the double bond itself is going to consist of Sigma bonds that connect the two carbons together and of course Pi bonds that allow for the double bond to exist and it's those Pi bond that kind of lock all the attached groups in place and the pi bond is going to create this really electron Rich region that prevents the groups from easily rotating around the bond where two well first of all I labeled it I labeled the sigma bond between the two carbons here and then the pi bonds which you can see here okay like those dumbbell shapes those are our piie bond so if you were to rotate the groups around the double bond the pi Bond would break and as you can see they're not in the same orientation but this requires a significant amount of energy so that's the reason why having that Pi Bond and that double bond kind of locks those groups into place and because of that restricted rotation it leads to two distinct geometric isomers the first is going to be the Cy isomer which we can see here and here and the next is going to be the trans isomer which you can see here so let's focus on the Cy isomers Cy isomers have two non-hydrogen groups on the same side of the double bond so first we identify where the double bond is for these carbons and we see we have two non-hydrogen groups that are on the double bond okay now often for us especially in our course we definitely are going to see two identical groups that are on the same side of the double bond okay folks so we see two methyl groups here and two chlorine groups here and then we have U nonidentical groups down here an bymers we're going to have two non-hydrogen groups on opposite sides of the double bond so we locate the double bond we see one nonhydrogen non-hydrogen group here and one nonhydrogen group here you also see our non-hydrogen chlorines on opposite sides here and then we have our different groups that they're still on opposite sides of the double bond as well so no matter what for a molecule to exhibit geometric isomerism of course you have to have that double bond and each carbon atom involved in the double bond must be bonded to two different groups so here we have a methyl groups here and then we have our hydrogens and we see these two groups on the same side now here yes we have different groups here but they are on the same side so that is going to be considered Sith as well again for our course we mainly focus on two identical groups but I'm also going to show you as much of the details as possible so when you get into organic chemistry and go go forward you're not like confused by new information any other isomers despite sharing the same molecular formula okay because they have different they're going to have different physical and chemical properties due to their spatial arrangement of their atoms now let's go back to our previous example to see if there's any F or trans isomerism that come out of that first example we have three methyl one pentin the first thing you want to do if you trying to identify ishm is find that double bond so we have our double bond here and I'm just going to call it out we have a carbon with two hydogen is attached then we're going to have our double bond and then we have this carbon attached to a hydrogen and then of course I'm going to label this entire thing in our group all right and so when we're thinking about isomerism and we ask yourselves does this exhibit through trans isomerism we know we have to have two distinct groups so we have hydrogens right but we only have one R Group here if we had another R Group then yes we can say this is fifth isomerism but because there's three hydrogens here and only one distinct R group that does not qualify so this is definitely not C or trans it does not exhibit geometric isomer now let's look at our next example six methyl 3 heptin first let's figure out where our um double bond is so we have our double bond here carbon double bond to carbon we have an R Group here we have an R Group here and then we have hydrogen and hydrogen this does exhibit um cyst isomerism because we have two R groups on the same side again sometimes our groups are identical which is mainly what we're going to see as far as our actual exams or tests but here our R groups are different no matter what they are on the same side so this can be considered CIS um isomerism that we're looking at and so as you go up higher in organic chemistry you'll know that you actually can write out cis- 6-methyl D3 demp as your full um naming for this now for our course we will not be doing CIS or trans naming just like I said before but when you get into organic chemistry yes you're going to be probably required to start naming with CIS or training so just keep that in mind h