Of the two procedures just described, preparation and carboxylation of a Grignard reagent...

Of the two procedures just described, preparation and carboxylation of a Grignard reagent or formation and hydrolysis of a nitrile, only one is appropriate to each of the following RX → RCO2H conversions. Identify the correct procedure in each case, and specify why the other will fail.

(a) Bromobenzene → benzoic acid

(b) 2-Chloroethanol → 3-hydroxypropanoic acid

(c) fert-Butyl chloride → 2,2-dimethylpropanoic acid

Sample Solution (a) Bromobenzene is an aryl halide and is unreactive toward nucleophilic substitution by cyanide ion. The route C6H5Br → C6H5CN → C6H5CO2H fails because the first step fails. The route proceeding through the Grignard reagent is perfectly satisfactory and appears as an experiment in a number of introductory organic chemistry laboratory texts.