Final answer:
When benzoic acid is treated with fuming sulfuric acid, the expected major product is meta-sulfobenzoic acid through a sulfonation reaction.
Step-by-step explanation:
When benzoic acid is treated with fuming sulfuric acid, the expected major product is benzenesulfonic acid. The reaction taking place is known as sulfonation, a type of electrophilic aromatic substitution where a hydrogen atom on the benzene ring of benzoic acid is replaced by a sulfonyl group (-SO3H). This reaction occurs as the sulfuric acid provides the sulfur trioxide (SO3) needed to carry out the sulfonation. The benzoic acid, with its -COOH functional group, typically directs new substituents to the meta position relative to the existing carboxyl group. Therefore, the product of such a reaction would be meta-sulfobenzoic acid, though reaction conditions can alter the outcome significantly.