The chemistry of anhydrides is similar to that of acid chlorides, although they react more slowly. A nucleophile attacks the carbonyl group to form a tetrahedral intermediate, and proton transfer to and from solvent primes the other half of the anhydride for elimination. Subsequent collapse of the tetrahedral intermediate with expulsion of the carboxylic acid yields the product ester. Draw curved arrows to show the movement of electrons in this step of the mechanism.