Acyl chlorides, also known as acid chlorides, are organic compounds derived from carboxylic acids by replacing the hydroxyl group (-OH) with a chlorine atom. They have the general formula RCOCl, where R represents an alkyl or aryl group. Acyl chlorides are typically colorless liquids with a pungent odor and are highly reactive, making them useful in various chemical reactions. These compounds are commonly used in the synthesis of esters, amides, and anhydrides. Due to their reactivity, acyl chlorides can easily react with alcohols, amines, and water, leading to the formation of these important organic compounds.