Aksyylkloridit

Aksyylkloridid (acyl chlorides) are a class of organic compounds in which the hydroxyl group of a carboxylic acid is replaced by chlorine. They have the general formula R-CO-Cl, where R is an alkyl or aryl group. Acyl chlorides are highly reactive and widely used as versatile intermediates in organic synthesis.

Most aksyylkloridid are prepared from carboxylic acids by reaction with reagents such as thionyl chloride (SOCl2), oxalyl chloride (COCl)2, or phosphorus pentachloride (PCl5). A common route is R-CO2H + SOCl2 → R-COCl + SO2 + HCl, often with catalytic DMF to speed the reaction. The process requires dry conditions to prevent hydrolysis.

Chemically, acyl chlorides are activated toward nucleophilic acyl substitution. They hydrolyze readily in water to give carboxylic acids: R-CO-Cl + H2O → R-CO2H + HCl. They react with alcohols to form esters and with amines to form amides. They can also react with carboxylates to yield anhydrides. Their reactivity and relative ease of forming derivatives make them valuable reagents, with physical properties that vary but many are reactive liquids or low-boiling compounds.

Applications include the preparation of esters, amides, and anhydrides, as well as common intermediates in pharmaceutical, dye, fragrance, and polymer syntheses. Acyl chlorides are widely used to introduce the acyl group into substrates and to activate carboxylic acids for further transformation.

Safety and handling: aksyylkloridid are corrosive and often lachrymatory. They react with water, releasing HCl (and sometimes SO2), so they must be handled under dry, inert conditions in a fume hood and stored in tightly closed, moisture-free containers.