Ester 5:

Problem:

Solution:

The reagent in this reaction is thionyl chloride (SOCl₂). Thionyl chloride and phosphorus pentachloride (PCl₅) are common reagents for the formation of acyl chlorides, in this instance benzoyl chloride from benzoic acid. Acyl chlorides are invariably prepared from carboxylic acids. They react with alcohols to form esters, primary and secondary amines to afford amides and water to regenerate a carboxylic acid. Draw a mechanism for the transformation of benzoic acid (1) to benzoyl chloride (2). Click here.