Organic Chemistry – Some Basic Principles Part 1

Compound, which obey Huckel rule, (4n+2)π is called aromatic compound.
Compound, which obey 4nπ rule, is called anti-aromatic compound.
Compound which contain one or more sp3 carbon in its structure is called non-aromatic compound.
The nature of following ions/compounds are as follows :Only (a) is non-aromatic and rest all are aromatic.