Chapter 21.SE, Problem 36MP

When 4-dimethylaminopyridine (DMAP) is added in catalytic amounts to acetic anhydride and an alcohol, it significantly increases the rate of ester formation. The process begins with a reaction between acetic anhydride and DMAP to form a highly reactive acetylpyridinium intermediate that is more reactive than acetic anhydride itself. Propose a mechanism for this process that includes the formation and reaction of the acetylpyridinium intermediate.