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Naming organic compounds
The basic rules
There are some general rules which you should remember when naming organic
compounds.

The longest unbranched chain containing the functional group is the parent
molecule, or simply the longest unbranched chain for alkanes. Remember that, the
longest chain can go round a bend.
 Indicate the position of the functional group with a number, numbering from the
end nearest the functional group.
 Name the branches, and indicate the number of branches. Example
 Methyl indicates there is 1 carbon atom
 Ethyl indicates there are 2 carbon atoms in the branch.
 The prefix 'di' indicates there are 2 branches.
 The prefix 'tri' indicates there are 3 branches.
Indicate the position of the branches with a number, numbering from the end nearest the
functional group.
For more than one branch, the branches are identified in alphabetical order, ignoring
any 'di', 'tri', etc, prefixes.
Each branch needs to be numbered individually, even if they are attached to the
same carbon atom.
The rule is a comma between numbers, and a dash between numbers and letters.
Naming alkanes, alkenes and alkynes
Alkanes
The alkanes don't contain a functional group and so the branches are numbered from
the end that gives the lowest set of position numbers for the branches.
Use the above rules, to see how the names of the alkanes below are built up.
Alkenes and alkynes
The functional group in the alkenes is the carbon-to-carbon double bond.
The functional group in the alkynes is the carbon-to-carbon triple bond.
The basic rules of naming apply.
The position of the double or triple bond is indicated by a number before the '-ene' or 'yne' part of the name.
For example:
Naming alcohols, aldehydes and ketones
Alcohols
The functional group in the alcohols is the hydroxyl group (-OH).
Alcohols end in the letters '-ol'.
The basic rules of naming apply.
The position of the hydroxyl functional group is indicated by a number before the '-ol'
part of the name.
Alcohols can also be termed primary, secondary or tertiary.
Primary has the -OH on the end of a chain.
Secondary has the -OH on a non-branched carbon atom along the chain.
Tertiary has the -OH on a branched carbon atom along the chain.
For example:
Aldehydes
All aldehydes contain a carbonyl functional group. The carbonyl group will never have
a position number in an aldehyde, as it is always on the end of the carbon chain.
Aldehydes end in the letters '-al'.
The basic rules of naming apply.
For example:
Ketones
Ketones also contain a carbonyl functional group, but in ketones it is never on the end
of a carbon chain.
Ketones end in the letters '-one'.
The naming rules apply, as before.
For example:
Naming carboxylic acids and esters
Carboxylic acids
Carboxylic acids contain the carboxyl functional group (-COOH). The carboxyl group
will never have a position number in a carboxylic acid, as it is always on the end of the
carbon chain.
Carboxylic acids end in '-oic acid'. The basic rules of naming apply.
For example:
Esters
An ester is made from an alcohol and a carboxylic acid.
Esters have their own rules for naming.
The first part of the name comes from the alcohol, and it ends with the letters '-yl'.
The second part of the name comes from the carboxylic acid, and it ends with the letters
'-oate'.
For example:
Name of Alcohol Name of Carboxylic acid Name of ester
ethanol
propanoic acid
ethyl propanoate
butanol
methanoic acid
butyl methanoate
pentanol
ethanoic acid
pentyl ethanoate
It is also possible to form names from structures.
The ester is divided between the carbon and oxygen in the ester functional group.
The acid part contains the carbonyl group.
For example: