Acyl chlorides are carboxylic acid derivatives. Ethanoyl chloride CH3COCl can be prepared by reacting ethanoic acid with phosphorus V chloride - PCl5, phosphorus III chloride - PCl3 or thionyl chloride - SOCl2. The acyl chloride can be separated by fractional distillation.PCl5 + CH3COOH → CH3COCl + POCl3 + HClSOCl2 + CH3COOH → CH3COCl + SO2 + HClPCl3 + 3CH3COOH → 3CH3COCl + H3PO3Hydrolysis of acyl chlorides produces the corresponding carboxylic acid. The carbonyl group reacts with nucleophiles in an addition-elimination reaction.