Carboxylic acids are named according to the International Union of Pure and Applied Chemistry (IUPAC) nomenclature by replacing the final ‘e’ of the parent alkane name with ‘oic acid’.

In the IUPAC system, the naming of carboxylic acids begins with identifying the longest carbon chain that contains the carboxyl group (-COOH). This chain is classified as an alkane, which consists solely of carbon and hydrogen atoms connected by single bonds. To derive the name of the carboxylic acid, the final ‘e’ of the alkane name is substituted with ‘oic acid’. For instance, a carboxylic acid with a two-carbon chain is referred to as ‘ethanoic acid’, which is derived from ‘ethane’.

The carbon atom of the carboxyl group is designated as carbon 1, and the remaining carbons in the chain are numbered sequentially. This numbering is crucial when identifying the positions of any additional functional groups or side chains. In cases where there are multiple carboxyl groups, the suffix ‘oic acid’ is modified: it becomes ‘dioic acid’ for two carboxyl groups, ‘trioic acid’ for three, and continues in this manner. The positions of the carboxyl groups are indicated by their corresponding numbers. For example, a three-carbon chain with carboxyl groups on the first and third carbons is named ‘propane-1,3-dioic acid’.

When a carboxylic acid acts as a substituent on a larger molecule, it is referred to as a ‘carboxy’ group, and the ‘oic acid’ ending is omitted. For example, a compound with a two-carbon chain, where the carboxyl group is located on the second carbon and a methyl group is on the first, is named ‘2-carboxypropane’.

In summary, the IUPAC rules for naming carboxylic acids involve identifying the longest carbon chain that includes the carboxyl group, replacing the final ‘e’ of the related alkane name with ‘oic acid’, and numbering the chain starting from the carboxyl carbon. Any additional functional groups or side chains are then named and positioned accordingly.