Anilides

Anilides are a class of amide compounds in which the amide nitrogen is bonded to an aryl group derived from aniline. In common form, they have the general structure R-CO-NH-Ph, where Ph represents a phenyl ring and R is an acyl substituent. The simplest member is acetanilide (CH3-CO-NH-Ph). More broadly, anilides are considered N-aryl amides of carboxylic acids, and they are typically prepared by acylation of aniline with acyl chlorides, anhydrides, or activated carboxylic acid derivatives under basic conditions.

Properties of anilides vary with the substituents on the acyl and aryl rings. They are usually solids with moderate to low water solubility and a range of melting points. Some anilides are relatively stable to air and moisture, while others hydrolyze to give the corresponding carboxylic acid and aniline under acidic or basic conditions.

Uses and examples of anilides span pharmaceuticals and agriculture. The best-known anilide is acetanilide, historically used as an analgesic and antipyretic; related compounds such as phenacetin and acetaminophen (paracetamol) are also N-acylated anilines with analgesic activity. In agriculture, several anilide derivatives are employed as herbicides, particularly N-arylpropionanilide-type compounds. In organic synthesis, anilides function as intermediates and protecting groups for amines, as well as reagents for acyl transfer.

Safety considerations include potential toxicity from hydrolysis to aniline, a compound with known health hazards. Proper handling and disposal are important, and some anilide derivatives have been restricted or withdrawn due to safety concerns.