A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to g...

A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.

(a) Propose a mechanism to show how the reaction of ethyl formate with an excess of allylmagnesium bromide gives, after protonation, hepta-1,6-dien-4-ol.

(b) Show how you would use reactions of Grignard reagents with ethyl formate to synthesize the following secondary alcohols.

(i) pentan-3-ol (ii) diphenylmethanol (iii) trans,trans-nona-2,7-dien-5-ol