Show how you would accomplish the following synthesis.

(a) Acetphenone→ acetophenone cyanohydrin

(b) Cyclopentancarbaldehyde→ 2-cyclopentyl-2-hydroxyacetic acid

(c) Hexan-1-ol →2-hydroxyheptanoic acid

Acetophenone on reaction with hydrogen cyanide undergoes nucleophilic addition reaction. Cyanide ion acts as a nucleophile and attacks at the carbonyl carbon which is electrophilic in nature and we get acetophenone cyanohydrin as the product.

Acetophenone Acetophenone cyanohydrin

Cyclopentancarbaldehyde on reaction with hydrogen cyanide undergoes nucleophilic addition reaction of cyanide ion onto the carbonyl carbon of aldehyde. Cyanohydrin gets formed which on hydrolysis yields 2-cyclopentyl-2-hydroxyacetic acid. Cyano group gets converted to acid functional group on hydrolysis.

2-cyclopentyl-2- hydroxyacetic acid

Hexan-1-ol on treatment with PCC which is an oxidizing agent, gets converted to hexanal. PCC oxidises alcoholic functional group to aldehyde. On addition of hydrogen cyanide in next step, hexanal undergoes nucleophilic addition reaction of cyanide ion onto carbonyl carbon of aldehyde which leads to generation of cyanohydrin and further hydrolysis yields required product, that is, 2-hydroxyheptanoic acid.

2-hydroxyheptanoic acid