Acyl anhydrides are compounds that are widely used in organic chemistry. These compounds are highly reactive and often used as intermediates in the synthesis of various organic compounds including esters, amides, and carboxylic acids. Other common synonyms used to refer to acyl anhydrides are carboxylic anhydrides, acid anhydrides or mixed anhydrides. Acyl anhydrides are formed by the reaction of two molecules of carboxylic acids with the elimination of one molecule of water. These compounds are commonly used as reagents in organic synthesis and are also utilized as catalysts in several chemical reactions. They are highly versatile and have a wide range of applications in the pharmaceutical, agrochemical and fine chemical industries.