According to IUPAC, the carboxylic acid comes first in priority order for functional groups, while anhydride has no prefix. Then how do you name a compound which contains both a carboxylic acid and an anhydride in it?


1 Answer 1


Acids are senior to anhydrides; therefore, a compound that contains both functional groups is named as acid.

The acid is substituted using the usual principles of substitutive nomenclature. The prefix ‘oxo’, denoting $\ce{=O}$, is used to indicate a carbonyl group when the group cannot be cited as suffix. The group $\ce{R-CO-O-{}}$ is indicated by an acyloxy prefix (e.g. ‘acetyloxy’, ‘propanoyloxy’, etc.).

For example: 3-(acetyloxy)-3-oxopropanoic acid

3-(acetyloxy)-3-oxopropanoic acid

(Cyclic anhydrides, however, are named as heterocyclic pseudo ketones.)

  • $\begingroup$ But isn't acetyl used when writing common name? Should be 'ethanoyl-oxy-propanoic acid' I think. $\endgroup$
    – user282856
    Commented Sep 22, 2016 at 17:37
  • 2
    $\begingroup$ @user282856 According to current IUPAC recommendations (2013), acyl groups from the carboxylic acids that have retained names are used as preferred prefixes. Since ‘acetic acid’ is the preferred IUPAC name, ‘acetyl’ is the preferred prefix. The corresponding systematic alternatives ‘ethanoic acid’ and ‘ethanoyl’ may be used in general nomenclature. The name ‘acetyloxy’ is the preferred prefix for the group $\ce{CH3-CO-O-{}}$; the contracted name ‘acetoxy’ may be used in general nomenclature. $\endgroup$
    – user7951
    Commented Sep 22, 2016 at 18:02
  • $\begingroup$ Are the parentheses mandatory? $\endgroup$
    – DHMO
    Commented Sep 22, 2016 at 23:49
  • 2
    $\begingroup$ @user34388 Yes, parentheses are used around compound prefixes as in ‘3-(acetyloxy)’ (‘acetyloxy’ = ‘acetyl’ + ‘oxy’) or ‘(chloromethyl)benzene’ (‘chloromethyl’ = ‘chloro’ + ‘methyl’), but not around the contracted prefix ‘acetoxy’, which may be used in general nomenclature. $\endgroup$
    – user7951
    Commented Sep 23, 2016 at 10:48

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