Question

What ester and Grignard reagent are needed to synthesize each alcohol?

a.

b.

Short answer

a.

b.

Step-by-step solution

 Step 1: Formation of tertiary alcohol from ester

Tertiary alcohol formed from an ester and a Grignard reagent must have two identical R (alkyl) groups, and this R group comes from the Grignard reagent RMgX.

All other carbons come from the ester group.

Preparation mechanism

(a) Alkyl 4-methylpentanoate reacts with an excess of methyl magnesium bromide in the presence of water gives the required tertiary alcohol product.

The reaction of Alkyl 4-methylpentanoate with methyl magnesium bromide

(b) Alkyl ethanoate reacts with an excess of butyl magnesium bromide in the presence of water to give the required tertiary alcohol product.

The reaction of Alkyl ethanoate with butyl magnesium bromide