The correct IUPAC name of
2-Carboxy propane-1, 3-dioic acid
1, 2, 3-Propanetrioic acid
1, 2, 3-butanetrioic acid
clearly there is no way we can choose the longest chain without excluding one −O||C−OH or -COOH
group.In this can we do not count any of the -COOH carbons as part of the primary chain.Instead ,all
three −O||C−OH groups are treated as substituents
-COOH is carboxylic acid group.
There are three of them ,each replacing a Hydrogen atom of a methane molecule.
Hence the IUPAC name is
(a) methane -tri-carboxylic acid
Note:methane - tri-carboxylic is one word.