The reaction between acetic acid CH3COOH and thionyl chloride SOCl2 to form acetyl chloride CH3COCl is an acid chloride formation reaction. The mechanism for this reaction is as follows:1. Nucleophilic attack: The oxygen atom of the acetic acid's carbonyl group C=O acts as a nucleophile and attacks the electrophilic sulfur atom of thionyl chloride SOCl2 . This forms an intermediate with a tetrahedral sulfur center.2. Leaving group departure: The chloride ion Cl- from thionyl chloride acts as a leaving group, and the sulfur-oxygen bond in the intermediate breaks, releasing a molecule of sulfur dioxide SO2 and forming an acyl chloride intermediate.3. Proton transfer: The acyl chloride intermediate undergoes a proton transfer, with the chloride ion Cl- acting as a base to abstract a proton from the -OH group, forming a molecule of hydrochloric acid HCl .4. Formation of acetyl chloride: The final product, acetyl chloride CH3COCl , is formed as the chloride ion Cl- attacks the carbonyl carbon, displacing the hydroxyl group OH- and forming a new carbon-chlorine bond.Overall, the reaction can be summarized as:CH3COOH + SOCl2 CH3COCl + SO2 + HClThis reaction is a common method for converting carboxylic acids into their corresponding acid chlorides, which are important intermediates in organic synthesis.