Anhydrides come from condensing two molecules of carboxylic acids. The condensation of two molecules of the same acid gives rise to symmetrical anhydrides, which are named by replacing the word acid with anhydride .



Asymmetric anhydrides -formed from two different acids- are named by citing the acids alphabetically.



Cyclic anhydrides—formed by cyclization of a diacid—are named by changing the word acid to anhydride and ending the name en- dioic .