Definition: In organic chemistry, acylation refers to a chemical reaction that adds an aryl halide onto the nitrogen in a benzene ring. This can be performed by both nucleophilic substitution (a.k.a. C1 substitution) or ahyloxylation. Nucleophilic substitution (also known as C1 substitution) is one of the most common reactions used in acylation, and it involves replacing one atom with another with the aim to achieve an intermediate that reacts with nitrogen to produce a secondary product. This typically requires a small number of carbons or a high degree of substituents on the nitrogen. The acyl halide (in this case, a hydrazine) is attached to the nitrogen group in a benzene ring. When the acyl halide binds and forms an ionic bond with nitrogen in the benzene, it can form a secondary product that reacts with the nitrogen to produce an intermediate that then undergoes a series of reaction steps leading to the desired primary product. Ahyloxylation (also known as hydrazolysis) is another way in which acylation occurs. In this case, a hydroxyl group attached to the nitrogen in a benzene ring is replaced by an ionic bond with another hydroxide or hydronium ion. This typically requires more than one carbonyl group and involves the use of organic acids that react with nitrogen. The resulting intermediate can then undergo a series of reaction steps leading to the desired primary product. Both nucleophilic substitution and hyloxylation are important reactions in acylation, as they allow for the addition of aryl halides onto the nitrogen in benzene without having to resort to more complex reagents like carbonyls or alkynes.

acylation