CH3COCl

Acetyl chloride, with the chemical formula CH3COCl, is an organochlorine compound and an active acyl chloride. It is a colorless, highly volatile liquid that fumes in air and has a sharp, acrid odor. It is extremely reactive with moisture, and exposure can cause severe burns to skin and eyes. In contact with water or alcohols it rapidly hydrolyzes, releasing hydrogen chloride and forming acetic acid.

As a reagent, CH3COCl is a versatile acetylating agent in organic synthesis. It reacts with alcohols to give esters (acetates) and with amines to form amides, both with concomitant production of HCl. It is generally more reactive than acetic anhydride because chloride is a good leaving group. Uses include preparation of acetylated derivatives in pharmaceuticals, fragrances, and polymers, as well as serving as a key step in various synthetic routes.

Preparation typically involves converting acetic acid to the corresponding acyl chloride. Industrial routes include the reaction of acetic acid with chlorinating agents such as thionyl chloride (SOCl2) or phosphorus halide reagents, producing acetyl chloride along with byproducts like SO2 and HCl. Laboratory methods may also employ related chlorinating reagents to convert carboxylic acids to acyl chlorides.

Storage and safety considerations are critical. Acetyl chloride should be kept in dry, tightly closed containers under appropriate ventilation, away from moisture, bases, and heat. It is highly corrosive and emits irritating fumes; handling usually requires a fume hood, protective gloves, and eye protection. It reacts vigorously with water, alcohols, and amines, so it must be used with care to avoid unwanted hydrolysis and corrosion.