Acylation

(organic chemistry) Any process whereby the acyl group is incorporated into a molecule by substitution.

A process in which a hydrogen atom in an organic compound is replaced by an acyl group (RCO, where R = an organic group). The reaction involves substitution by a nucleophile (electron donor) at the electrophilic carbonyl group (C&dbnd;O) of a carboxylic acid derivative. The substitution usually proceeds by an addition-elimination sequence. Two common reagents, with the general formula RCOX, that bring about acylation are acid halides (X = Cl, Br) and anhydrides (X = OCOR). There are also other acylating reagents. The carboxylic acid (X = OH) itself can function as an acylating agent when it is protonated by a strong acid catalyst as in the direct esterification of an alcohol. Typical nucleophiles in the acylation reaction are alcohols (ROH) or phenols (ArOH), both of which give rise to esters, and ammonia or amines (RNH₂), which give amides. See also Acid anhydride; Acid halide; Amide; Amine; Electrophilic and nucleophilic reagents.

Introduction of an acyl radical into the molecules of a compound.

In chemistry, acylation (rarely, but more formally: alkanoylation) is the process of adding an acyl group to a compound. The compound providing the acyl group is called the acylating agent.

Because they form a strong electrophile when treated with some metal catalysts, acyl halides are commonly used as acylating agents. For example, Friedel-Crafts acylation uses acetyl chloride (ethanoyl chloride), CH₃COCl, as the agent and aluminum chloride (AlCl₃) as a catalyst to add an ethanoyl(acetyl) group to benzene:

The mechanism of this reaction is electrophilic substitution.

Acyl halides and anhydrides of carboxylic acids are also commonly used acylating agents to acylate amines to form amides or acylate alcohols to form esters. The amines and alcohols are nucleophiles; the mechanism is nucleophilic addition-elimination. Succinic acid is also commonly used in a specific type of acylation called succination. Oversuccination occurs when more than one succinate adds to a single compound.

See also

• acetyl
• ketene
• indicator
• chemical synthesis

References

• NIH Thesaurus

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