R1COCl

R1COCl is a general chemical formula representing an acyl chloride. An acyl chloride is an organic compound derived from a carboxylic acid by replacing the hydroxyl group (-OH) with a chlorine atom (-Cl). The 'R1' in the formula signifies a hydrocarbon group or a hydrogen atom. This means the simplest acyl chloride is formyl chloride (R1=H), although it is highly unstable. More common examples include acetyl chloride (R1=CH3) and benzoyl chloride (R1=C6H5).

Acyl chlorides are highly reactive compounds. The carbonyl carbon atom is electrophilic due to the electron-withdrawing effect of both the oxygen atom and the chlorine atom. This makes them susceptible to nucleophilic acyl substitution reactions. They readily react with water to form the parent carboxylic acid and hydrochloric acid. They also react with alcohols to form esters and with amines to form amides. These reactions are often vigorous and exothermic. Due to their reactivity and irritating nature, acyl chlorides are typically handled with care in laboratory settings. They are important intermediates in organic synthesis, used for the preparation of esters, amides, and other carboxylic acid derivatives.