this video is all about relating the structures and names of organic compounds chemists Pharmacists and other scientists need to be able to interpret a compound name to get the structure of a compound if a new compound is synthesized or discovered the scientist needs to be able to use its structure to formulate a name for it but since there are tens of millions of known organic compounds with new ones being discovered all the time and some are rather complex in nature we need a very systematic way of naming these organic molecules to prevent confusion a group of scientists formed the international Union of pure and applied chemistry or IUPAC for short and devised systematic naming rules which are used by scientists all over the world their naming rules are called IUPAC nomenclature let's have a look at some different classes of compounds and use IUPAC nomenclature to name molecules in these classes the simplest organic compounds contain only carbon and hydrogen atoms these molecules are called hydrocarbons carbon hydrogen bonds are always single bonds but pairs of carbon atoms may form single double or triple bonds the class of compounds called alkanes are hydrocarbons whose carboncarbon bonds are all single bonds each carbon atom in an alkane molecule forms four single bonds this carbon has four single bonds so does this one and this one too alkanes are described as being saturated as all of the carbon atoms form the maximum number of single bonds the molecule is saturated because no more single bonds can be formed alkanes are mostly found in fossil fuels such as coal petroleum also called crude oil and natural gas petrol and Diesel which we get from crude oil contain high levels of alkanes for linear alkanes the root name indicates the number of carbon atoms in the chain so to name a linear alkane we start by finding the longest carbon chain to get the root the name of an alkane always ends with the suffix a using this table we can see that for example when there are four carbon atoms in the chain the prefix or root is but and with a suffix of a the the name is thus butane this name is called the IUPAC name of the compound as it follows the rules set out by the international Union of purine applied chemistry butane is a linear alkane we can see this from its structure here is another example when there are two carbon atoms in the chain the root is f and the aupc name is ethane ethane is a linear cane we need to know the roots are meth eth prop but pent for the first five linear alanes respectively and hex hept o non and deck for the next five again the suffix is a for alkanes if a carbon atom in an alkane forms bonds to three or four other carbon atoms the molecule is not linear but branched to name a branched alkane first the longest chain of carbon atoms must be identified any other carbon chains are branches or side chains the longest chain gives the root name and we can use the same table as before in this example the longest carbon chain contains five carbon atoms so the root is pent since alkanes have fully saturated carbon atoms the suff of the root name will end with a the longest chain must be numbered from the end closest to the branch or side chain so we number the chain like this not like this the side chain must be on the lowest carbon number possible each side chain or branch is listed at the start of the name as a prefix to deduce this portion of the name we use the table again this time we refer to the side chains as alkal groups and their names end in y l this side chain has one carbon atom and so the prefix is methyl if the side chain could be placed in more than one position on the longest chain its location must be indicated by a number and a hyphen in front of the name since the methyl side chain is on carbon number two of the longest chain we write 2- methyl pentane note that if there is only one possible position for the side chain as in this example A number is not needed in the name this compound methyl propane does not need a 2- prefix note also that if the side chain is moved to carbon number three we get a totally different compound butane which is in fact a four carbon chain not a three carbon chain with a side group going back to the example we were working with two methyl pentane let's add another methyl side chain if there are two or more side chains of the same type as in this case the corresponding prefix must begin with di Tri Tetra Etc to indicate the number of side chain present and their positions are listed before the corresponding prefix in ascending order and separated with commas for example this compound is 2a3 dimethyl pentane if there are two or more side chains of different types their prefixes must be placed in alphabetical order regardless of their positions the letter determining the order is the first letter of the side chain type excluding prefixes such as D and try for example the name of this compound is 3 ethyl 2 methyl pentane a compound is unsaturated if it contains carboncarbon double bonds or carboncarbon triple bonds the carboncarbon double bond is called an alkanol group and a compound containing this group is an alen a carboncarbon triple bond is called an alyal group and a compound containing this group is an alkine the rules for naming alkenes and alkin are similar to those for alkanes but we must ensure the unsaturated bonds are included in the longest chain so the longest chain used for the root name in this example is the chain with five carbon atoms and we get the root name pent and this is the side chain alken names end in in and so for this compound so far we have pentin for the name alkine names end in in when naming an alken or alkine with side chains the longest chain is numbered to make the position of the functional group as low as possible regardless of the side chain positions and if the carbon carbon double bond or carboncarbon triple bond could be in two or more different positions the position must be indicated with a number placed before the e or in suffix the number is the position of the first atom in the bond or the lowest number of the carbon atoms in the bond in the case where the double or triple bond can only occur in one position no number prefix is needed this is true for these examples propine and propine side chains are named and numbered as with alkanes the side chain here is the ethyl group on carbon number two and so the name of the compound is two ethyl pent one in naming halogeno alkanes follows similar rules to naming alkanes carbon hogen bonds are indicated with the prefixes in the table the position of the functional group is indicated with a number numbers are assigned as described for alkal groups this compound is two bromo one chloro four methyl pentane compounds with hydroxy groups are called alcohols they are named in a similar manner to alkanes except the name of an alcohol ends with the suffix o for example this compound is ethanol in these next two examples we can see that an alcohol chain is numbered from the end closest to the hydroxy group the position of the the hydroxy group is indicated with a number placed before the old suffix with hyphens these two compounds are butan 1 o and butan 2 O respectively a carbon oxygen double bond in an organic compound is termed a carbon group there are several different classes of compounds with carbonal groups and only three are shown here when naming a carbonal compound it is important to remember that the carbon atom of the carbonal group contributes to the length of the carbon chain naming these three carbonal compounds shown is similar to naming other organic compounds where we find the longest chain and number the longest chain starting from the end closest to the functional group if the carbon atom of the carbonal group is attached to a hydrogen atom and either a carbon atom or another hydrogen atom it is termed an alahh group and compounds containing alahh groups are also called alahh alahh are named using the suffix L alahh groups always occur at the end of a chain and so the position of the alahh group is not indicated with a number for example this four carbon alahh is butanal if the carbon atom of the carbonal group is attached to two other carbon atoms it is termed a ketone group compounds containing Ketone groups are also called ketones ketones are named using the suffix own if there is only one possible position for the Ketone group we don't need to indicate the position of the carbonal in the name this compound name is just butanone however if the Ketone group could be placed in two or more different positions the position is indicated with a number before the suffix for example the Ketone on the left is pentan 2 own and the one on the right is pentan 3 own when the carbon atom of a carbonal group is attached to a hydroxy group together this functional group is called a carboxy group compounds containing carboxy groups are called carboxilic acids carboxilic acids are named using the suffix OIC acid like alahh groups carboxy groups always occur at the end of a chain and so it is not necessary to indicate the position of the Cobar oxal group with a number for example this carboxilic acid is butanoic acid other examples of carbonal compounds are the classes Esters and amides but we won't study these further here now let's summarize the rules of aupac nomenclature we learned that the longest carbon chain which includes the functional group if there is one gives us the root name of the compound the class of compound which we get from the type of functional group is given a specific suffix in the name we number the longest chain from the end closest to the functional group except for halogeno alkanes the position of the functional group is written after the root but before the suffix with hyphens this does not apply to alides and carboxilic acids whose functional group is always on carbon number one if the compound is a branched alkane or a halogeno alcane the names and positions of the side chains and halogens are indicated as a prefix using D or try Etc if there is more than one of the same type and different types are listed alphabetically