Question

: Which of the following is a heterocyclic aromatic compound?
A.Benzene
B.Naphthalene
C.Pyridine
D.All of the above

Answer 1

A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as a member of its ring. Mostly, electronegative elements like nitrogen, oxygen and sulphur replace carbon in the ring to form heterocyclic aromatic compounds.

Complete step by step answer:
In the above question, all the compounds are aromatic compounds because they have delocalized structures and all of them obey the Huckel’s rule of aromaticity. But benzene is an aromatic compound of carbon that has only carbon and hydrogen atoms and no other atoms are present in it.
Coming to naphthalene, it has ten carbon atoms in its structure and besides that it has hydrogen atoms. Hence, this is also not a heterocyclic compound.
Coming to pyridine, in this compound there are five carbon atoms and besides that one nitrogen atom. Hydrogen atoms balance the tetravalency of carbon in the ring. Hence, as there are more than two different elements in this compound so this is a heterocyclic compound.

So, the correct answer is option C, pyridine.

Note:
There are different numbers of heteroatoms in the heterocyclic compounds and the study of the properties and the nature of these compounds is called heterocyclic chemistry. Examples of heterocyclic compounds include nucleic acids, majority of the drugs, most of the biomass, artificial and synthetic dyes, etc.
The molecules include three, four, five, six, seven, eight, and a lot more members in the heterocyclic ring. These structures are mostly formed from fusion of other rings, either carboxylic or heterocyclic.