Question

Consider the following compound and its name. Something is wrong in the given name. What is the mistake in naming the above compound?
2-cyclohexenoic acid

A.Numbering is done wrong
B.Position of double bond is not specified in the name
C.Position of \[ - COOH\] is not specified in the name
D.Suffix is used wrongly

Answer 1

Hint: The IUPAC system of nomenclature assigns a suffix to carboxylic acids. The –e ending of the hydrocarbon is removed from the name of the parent chain and is replaced with -enoic acid. When a carboxyl group is added to a ring the suffix -carboxylic acid is always added to the name of the cyclic compound. The carbon in the ring attached to the carboxyl group is given the first numbering.

Complete answer:
The name given for the above compound as 2-cyclohexanoic acid is incorrect. The suffix "-oic acid" is used only for open chain carboxylic acids. For a cyclic system, the suffix is always "carboxylic acid". Therefore we can say that the name of the given compound should be cyclohex-2-enecarboxylic acid.
Thus we can say that the suffix was not used properly in the name given to us.
Therefore, the correct answer is option D.

Note:
Carboxylic acids have the highest priority among carbon-containing functional groups. Double bond always comes after that. In naming a molecule, the chain numbering starts from the end closest to either group. This is unless they're both equidistant from the chain ends, in which case the double bond takes priority and is given the lower number.