JEE MainChemistryHydrocarbons
Consider the following two reaction sequences starting from toluene: Sequence 1: Toluene KMnO₄, H^+, P CH₃CH₂Cl, AlCl₃ Q Sequence 2: Toluene CH₃CH₂Cl, AlCl₃ R (major) KMnO₄, H^+, S Identify the final products Q and S. (Note: If a reagent fails to react, the starting material of that step is recovered as the product).
Options
- AQ is Benzoic acid; S is Benzene-1,4-dicarboxylic acid
- BQ is 3-Ethylbenzoic acid; S is 4-Ethylbenzoic acid
- CQ is 3-Ethylbenzoic acid; S is Benzene-1,4-dicarboxylic acid
- DQ is Benzoic acid; S is 4-Ethylbenzoic acid
Correct answer
A. Q is Benzoic acid; S is Benzene-1,4-dicarboxylic acid
Step-by-step solution
In Sequence 1, toluene is subjected to vigorous oxidation with KMnO₄ / H^+ and heat. The side-chain methyl group is oxidized to a carboxylic acid group, yielding benzoic acid as product P. Benzoic acid contains the strongly deactivating - COOH group, which reduces the electron density on the benzene ring significantly. As a result, it does not undergo Friedel-Crafts alkylation when treated with CH₃CH₂Cl and AlCl₃ . Thus, no reaction occurs in the second step, and Q remains benzoic acid. In Sequence 2, toluene first