Anhydrides

Anhydrides are the chemical reaction of two carboxylic acids, which produces an acid anhydride and a water molecule.

CH₃CH₂COOH + CH₃CH₂COOH → CH₃CH₂COOCOCH₂CH₃ + H₂O
propanoic acid + propanoic acid → hexanoic anhydride (propanoic propanoic anhydride)

Acid anhydrides are significant in organic chemistry as acid anhydrides are involved in esterification with alcohol as a reagent without an catalyst to form an ester.

(C₂H₅CO)₂O + CH₃ CH₂OH → CH₃CH₂COOH + CH₃CH₂COCH₂CH₃

hexanoic anhydride + ethanol → propanoic acid + ethyl propanoate

propanoic propanoic anhydride

Esters are used for industrial purposes as such as flavouring and perfumes.