IUPAC system and IUPAC rules of naming carboxylic acid

Since carboxylic acids are amongst the earliest organic compounds to be isolated from nature, a large number of them are known by their common names. The common names end with the suffix-ic acid and have been derived from Latin or Greek names of their natural sources. For e.g., formic acid (HCOOH) was first obtained from red ants (formica means ant), acetic and (CH₃COOH) from vinegar (acetum means vinegar) butyric acid (CH₃CH₂CH₂COOH) from rancid butter (butyrum means butter) caproic acid (CH₃CH₂CH₂CH₂COOH) from goats (caper means goat). The positions of the substitutes are indicated by Greek letters a, b, g, d etc the a-carbon being the one directly attached to the carboxyl group, b - the next and so on.

In the IUPAC system, the monocarboxylic acids are named as alkanoic acids. The name of the acid is derived by replacing the terminal 'e-' of the corresponding alkane with '-oic acid'. Carboxyl carbon is always given number one while numbering the carbon atoms of the parent chain.

Examples:

Common nomenclature

In the common system, cyanides are named by any of the following methods:

(i) By using suffix cyanide after the name of alkyl and aryl group.

or

(ii) By adding the suffix o-nitrile in place of ic - acid in the common name of the corresponding acid produced by the hydrolysis of the cyanide compound.

For e.g., CH₃ CN on hydrolysis gives CH₃ COOH i.e., acetic acid.

So the common name of the compound is methyl cyanide or Acetonitrile as derived from acetic acid.

IUPAC nomenclature

In the IUPAC system, suffix nitrile is added to the name of the hydrocarbon atoms ie they are named as Alkanenitriles. The carbon atom of the -CN group is also counted in the parent chain. For determining the position of the substituent in a chain, the nitrile carbon is numbered as 1.

Example: