Karbonyylihalidi

Karbonyylihalidi, commonly known as an acid halide, is an organic compound derived from a carboxylic acid by replacing the hydroxyl group (-OH) with a halogen atom (-X), where X can be fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). The general formula for a karbonyylihalidi is R-CO-X.

Karbonyylihalide structures feature a carbonyl group (C=O) bonded to a halogen atom. Due to the electronegativity of the halogen, the carbon atom of the carbonyl group is electron-deficient, making it highly susceptible to nucleophilic attack. This reactivity is a defining characteristic of karbonyylihalides.

The reactivity of karbonyylihalides is generally higher than that of other carboxylic acid derivatives like esters or amides. This is primarily because the halogen atom is a good leaving group. They readily undergo nucleophilic acyl substitution reactions with a variety of nucleophiles, including water, alcohols, amines, and Grignard reagents. For example, reaction with water yields the corresponding carboxylic acid and a hydrogen halide. Reaction with alcohols produces esters, and reaction with amines forms amides.

Karbonyylihalides are important intermediates in organic synthesis. They are often prepared from carboxylic acids using reagents such as thionyl chloride (SOCl2), phosphorus pentachloride (PCl5), or oxalyl chloride ((COCl)2). Because of their high reactivity, they are typically used immediately after preparation or stored under anhydrous conditions to prevent hydrolysis. The most common and widely used karbonyylihalide is acyl chloride, where the halogen is chlorine.