Identify the starting material for the following reaction:

Step-by-step solution

The reaction involves a di-Grignard reagent, BrMg-(CH ₂ ) ₄ -MgBr , reacting with a substrate to form a cyclic tertiary alcohol, 1-ethylcyclopentanol. For a Grignard reagent to add twice to the same carbon atom, the starting material must be an ester (or an acid halide). When an ester R-COOR ' reacts with a di-Grignard reagent BrMg-(CH ₂ ) _n -MgBr , it forms a cyclic alcohol with a ring size of n+1 . The mechanism proceeds in two main steps: 1. One nucleophilic end of the di-Grignard reagent attacks the ester carb