Question

Classify each structure as aromatic, antiaromatic, or nonaromatic. A B С D A: [Select] > B: [Select ] < C: [Select) D: [Select]

Answer 1

The aromatic, non-aromatic and antiaromatic ring can be determined by Huckel rule. According to this rule is the molecule is aromatic if it contains planar ring and (4n+2) pi electrons in a conjugated system (all ring atoms must be sp² hybridized). If a planar cyclic conjugated molecule contains 4n pi elections then the molecule will be antiaromatic.

If the cyclic molecule is nonplanar or it contains an sp³ hybrid carbon atom in the ring, the molecule will be non-aromatic.

Molecule	aromatic/antiaromatic/nonaromatic	explanation
A	Aromatic	This molecule contains planar ring having all carbon atoms sp2 hybridized. Number of pi electrons is (4*1+2 = 6) six and it obeys Huckel rule
B	Antiaromatic	This molecule contains planar ring having all carbon atoms sp2 hybridized. Number of pi electrons is (4*1= 4) four and according to Huckel rule it si antiaromatic
C	Nonaromatic	In the ring one carbon atom forms four single bonds, it's mean that this carbon atom is sp3 hybridized thus molecules do not contain conjugated ring system and it is nonaromatic
D	Aromatic	This molecule is a resonance structure of benzene and this molecule contains planar ring having all carbon atoms sp2 hybridized. Number of pi electrons is (4*1+2 = 6) six and it obeys Huckel rule