When a student treated butanedioic acid with thionyl chloride, she was surprised to find that the product she obtained was an anhydride rather than an acyl chloride. Propose a mechanism to explain why she obtained an anhydride.

Show how you would use an acid chloride as an intermediate to synthesize

(b) phenyl propionate (CH₃CH₂COOPh) from propionic acid and phenol.

Show how you would accomplish the following syntheses using amides as intermediates. You may use any necessary reagents.

(a) benzoic acid → benzyldimethylamine

(b) pyrrolidine → N-ethylpyrrolidine

(c) cyclopentanecarboxylic acid → cyclopentanecarbonitrile

Phosgene (COCl₂) was used as a poison gas in World War I. What product would be formed from the reaction of phosgene with each of the ­following reagents?

c. excess propylamine

d. excess water

Propose a mechanism for the reaction of benzoic acid with oxalyl chloride. This mechanism begins like the thionyl chloride reaction, to give a reactive mixed anhydride. Nucleophilic acyl substitution by chloride ion gives a tetrahedral intermediate that eliminates a leaving group, which then fragments into carbon dioxide, carbon monoxide, and chloride ion.

What reagents are required to carry out the following synthesis?

Predict the product of the following reactions.

(a)