Aromaticity Chemistry Of Aromatic Compounds

1. Formation of Electrophile: Chloromethane reacts with the Lewis acid (AlCl₃) to form the methyl carbocation (CH₃⁺).
2. Electrophilic Attack: The methyl carbocation attacks the phenol, primarily at the ortho and para positions due to the activating effect of the -OH group.
3. Formation of Products: The main products are o-cresol and p-cresol. The ortho and para positions are more reactive due to increased electron density from the hydroxyl group.

To determine which compound is non-aromatic, we need to check whether the compounds obey Hückel's rule for aromaticity, which states that for a compound to be aromatic, it must have a planar structure and a conjugated system of -electrons that follows the rule (where is a non-negative integer).
1. Compound [A]: - This is benzene ( ), which is aromatic as it has 6 -electrons ( , thus ).
2. Compound [B]: - This is furan, a heterocyclic compound with an oxygen atom in the ring. It has a conjugated system of 6 -electrons, but one of these electrons comes from the oxygen lone pair. According to the rules for aromaticity, furan is not aromatic because it doesn’t follow the rule perfectly in all conditions. Thus, it is non-aromatic.
3. Compound [C]: - This is pyrrole, which is aromatic. It has 6 -electrons (with the nitrogen lone pair participating), and it satisfies the rule.
4. Compound [D]: - This is thiophene, which is aromatic. It has 6 -electrons from the sulfur lone pair and conjugation, fulfilling the rule. Thus, the correct answer is (B) as furan is non-aromatic.