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An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid. In organic chemistry, organic acid anhydrides contain the functional group −C(=O)−O−C(=O)−. Organic acid anhydrides often form when one equivalent of water is removed from two equivalents of an organic acid in a dehydration reaction.
Therefore, the aromatic carboxylic acid anhydride and the mixed anhydride (MA) coexist in the system. Furthermore, aliphatic carboxylic acid anhydride produced via disproportionation of the MA is simultaneously present in the system; thus, it is directly used as a mixture without being separated.
First, the Lewis acid catalyst activates the TFBA, and then a carboxyl group in seco acid reacts with the activated TFBA to produce mixed anhydride (MA) once. Then, a carbonyl group derived from the seco acid in MA is selectively activated and is attacked by a hydroxyl group in the seco acid through intramolecular nucleophilic substitution.
A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O)) 2 O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. [2] Thus, (CH 3 CO) 2 O is called acetic ...
The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in equilibrium, and with loss of a water molecule (hence the name condensation). [3] The reaction may otherwise involve the functional groups of the molecule, and is a versatile class of reactions that can occur in acidic or basic ...
The pyrophosphate anion has the structure P 2 O 4− 7, and is an acid anhydride of phosphate. It is unstable in aqueous solution and hydrolyzes into inorganic phosphate: P 2 O 4− 7 + H 2 O → 2 HPO 2− 4. or in biologists' shorthand notation: PP i + H 2 O → 2 P i + 2 H +
Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO 3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. [6] This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water ...
Trifluoroacetic anhydride has various uses in organic synthesis. It may be used to introduce the corresponding trifluoroacetyl group, for which it is more convenient than the corresponding acyl chloride , trifluoroacetyl chloride , which is a gas.