The following additional rules are applied while naming organic compounds containing one functional group.
1) Parent chain : The parent chain must contain the functional group even when it does not denote the longest chain.
Take a look at the way numbering is done in the following compounds :
2) Numbering of the parent chain should always be done from that end which is nearer to the functional group.
3) When a carbon containing functional group such as -CHO, -COOH, -COCl is present at the terminal, the carbon of the functional group is always assigned number 1.
Compare the way numbering is done :
The suffix of the functional group is added to the end of the word root with its positional number.
Without any functional group
With a functional group
Note : Since 'ol' begins with a vowel, the terminal 'e' from primary suffix is dropped (already discussed in nomenclature introduction ).
When the same functional group appears more than once in the chain, suitable prefixes such as di (for two), tri (for three), tetra (for four) etc., are added along with their positional numbers.
Notice that 'e' from primary suffix 'ane' is retained because 't' is a consonant.
When the location of a functional group is 1 and there is no ambiguity, the '-1-' from the name can be omitted.
2-Ethylbutan-1-oic acid = 2-Ethylbutanoic acid
Ethane-1,2-diol ( '1' cannot be omitted from '-1,2-')