Question

Show how you would accomplish the following synthetic conversions by adding an organolithium reagent to an acid.

Short answer

Organolithium reagents can be used to synthesize ketones from given carboxylic acids. Being very reactive toward carbonyls, organolithium reagents attack the lithium salt of a carboxylate anion to form dianions. Again, hydrate is formed from the protonation of the dianion which loses water molecules to yield the carboxylic acid.

Step-by-step solution

Introduction

Organometallic compounds containing carbon-lithium bonds are known an organolithium reagent. Organolithium reagents are important in organic synthesis.

Synthetic conversion

(a)

Benzoic acid reacts with organolithium reagent to form a dianion which undergoes protonation to form a hydrate. The hydrate formed undergoes hydrolysis quickly to form ketone.

(b)

Bromo cyclopentane reacts with lithium to form cyclopentyl lithium. Then, carboxylic acid reacts with a desired organolithium reagent to form a dianion which undergoes protonation to form a hydrate. The hydrate formed undergoes hydrolysis quickly to form ketone.

(c)

Pentanoic acid reacts with organolithium reagent to form a dianion which undergoes protonation to form a hydrate. The hydrate undergoes hydrolysis quickly to form ketone (heptan-3-one).

(d)

Phenylacetic acid reacts with organolithium reagent to form a dianion which undergoes protonation to form a hydrate. The hydrate formed undergoes hydrolysis quickly to form ketone (3,3-dimethyl-1-phenylbutan-2-one).