Answer :
The reaction of an ester with a Grignard reagent involves nucleophilic acyl substitution to form a ketone intermediate, followed by nucleophilic addition and then an acid work-up to produce a tertiary alcohol.
The reaction mechanism of an ester with a Grignard reagent to form a tertiary alcohol is a multi-step process. Initially, the Grignard reagent performs a nucleophilic acyl substitution, replacing the OR' group of the ester with the alkyl group from the Grignard reagent, thereby forming a ketone.
This ketone is highly reactive and does not isolate; it undergoes a subsequent nucleophilic addition with a second equivalent of the Grignard reagent forming an alkoxide intermediate. Finally, an acid work-up protonates the alkoxide, generating the tertiary alcohol product. If the ester’s R group is a carbon group, the reaction will yield a tertiary alcohol as the product.
This reaction is a key transformation in organic synthesis, allowing for the construction of complex alcohol structures from simpler ester precursors. The general stoichiometry of the reaction can be summarized as follows: an ester reacts with two equivalents of a Grignard reagent, followed by an acid work-up, to produce a tertiary alcohol.
