In the IUPAC nomenclature system, carboxylic acids are named using different suffixes. The two most common suffixes used to name carboxylic acids are -oic acid and -carboxylic acid. But when should we use each of these suffixes?


The -oic acid suffix is used to name carboxylic acids that have a straight carbon chain. Some examples of carboxylic acids that are named using the -oic acid suffix include:

• Acetic acid (2 carbons)


• Butanoic acid (4 carbons)


• Decanoic acid (10 carbons)

When naming a carboxylic acid with the -oic acid suffix, the carbon chain is numbered from the carboxyl group. The carboxyl group is always assigned the number 1.


The -carboxylic acid suffix is used to name carboxylic acids that have a branched carbon chain. Some examples of carboxylic acids that are named using the -carboxylic acid suffix include:

• 2-Methylbutanoic acid


• 3-Ethylpentanoic acid


• 4-Isopropylheptanoic acid

When naming a carboxylic acid with the -carboxylic acid suffix, the carbon chain is numbered so that the carboxyl group is assigned the lowest possible number.


There are some exceptions to these naming rules. For example, formic acid (the simplest carboxylic acid with only one carbon atom) is not named using either the -oic acid or -carboxylic acid suffix. Instead, it is named using the systematic name methanoic acid. Similarly, the carboxylic acid derived from benzoic acid is named using the suffix -benzoic acid rather than -oic acid or -carboxylic acid.


In summary, the -oic acid suffix is used to name carboxylic acids with a straight carbon chain, while the -carboxylic acid suffix is used to name carboxylic acids with a branched carbon chain. However, there are some exceptions to these naming rules, and it is important to consult the IUPAC guidelines for naming carboxylic acids in specific cases.

If the carboxylic acid functional group is a part of parent chain then we can use -oic acid. then on the other hand, if it is not the part, or the carbon in the functional group is not counted in parent chain, then we can use -carboxylic acid,for example C6H11- COOH.here you can name it as cyclohexane carboxylic acid as per the rule.