Carboxylic Acids and their Derivatives

Acid Anhydrides Rule C-491

491.1 - Symmetrical anhydrides of monocarboxylic acids, when unsubstituted, are named by replacing the word "acid" by "anhydride".

Examples to Rule C-491.1

Note: In some languages the word "acid" is included before "anhydride".

491.2 - Anhydrides of substituted monocarboxylic acids, if symmetrically substituted, are named by prefixing "bis-'' to the name of the acid and replacing the word "acid" by "anhydride''. The "bis'' may, however, be omitted.

Examples to Rule C-491.2

491.3 - Mixed anhydrides (anhydrides of different monobasic acids) are named by giving in alphabetical order the first (i.e., the specific) part of the names of the two acids, followed by "anhydride''.

Examples to Rule C-491.3

491.4 - Cyclic anhydrides of polycarboxylic acids, although possessing a heterocyclic structure, are preferably named as acid anhydrides, as in Rule C-491.1 but with any necessary locants.

Examples to Rule C-491.4

See Recommendations'93 R-5.7.7

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