Atsüülhalogeniid

Atsüülhalogeniid, also known as acyl halide, is a class of organic compounds with the general formula RCOX, where R is an alkyl or aryl group, and X is a halogen atom (typically chlorine, bromine, or iodine). These compounds are derivatives of carboxylic acids, where the hydroxyl group (OH) is replaced by a halogen atom. Atsüülhalogeniidid are generally colorless liquids or solids with pungent odors. They are highly reactive due to the polarized carbon-halogen bond and the electron-withdrawing nature of the halogen. This reactivity makes them useful intermediates in organic synthesis.

The primary method of preparation for atsüülhalogeniidid involves the reaction of a carboxylic acid with a halogenating agent. Common reagents include thionyl chloride (SOCl2) for acyl chlorides, phosphorus tribromide (PBr3) for acyl bromides, and phosphorus pentachloride (PCl5) for acyl chlorides. Atsüülhalogeniidid readily undergo nucleophilic acyl substitution reactions. For instance, they react with alcohols to form esters, with amines to form amides, and with water to regenerate the parent carboxylic acid. Their high reactivity also means they must be handled with care, often in anhydrous conditions, as they can react violently with water.