Carboxylic Acid to Acid Chloride Practice Problems

Phosgene (COCl₂) is a toxic gas used as chemical weapon. Identify the product formed by the reaction of phosgene with acetic acid.

The reaction of pentanedioic acid with thionyl chloride results in an anhydride instead of an acyl chloride. Provide the mechanism for the formation of the anhydride.

Draw the mechanism for the reaction of 3-methylbutanoic acid and oxalyl chloride to form 3-methylbutanoyl chloride. The mechanism is similar to that of the reaction of thionyl chloride (SOCl₂) with a carboxylic acid. It starts with the formation of a mixed acid anhydride intermediate. This anhydride undergoes nucleophilic acyl substitution by the chloride ion, to remove the leaving group which further breaks into carbon dioxide, carbon monoxide, and chloride ion.