Esterification of Acid Halides

Because of their relative thermodynamic instability, acyl halides are good starting points for the formation of the whole array of carboxylic acid derivatives (carboxylic acids, amides, esters, or acid anhydrides). An alcohol, like water or ammonia, begins the reaction by donating an electron pair to the acyl carbon. An ester is formed when an alcohol performs as the nucleophile in an acyl substitution reaction.