The mechanism for this reaction involves the following steps: Diethyl malonate reacts with ethoxide ion to form enolate anion 1; 3-Hexene reacts with a peroxyacid to form epoxide 2; Enolate anion 1 reacts with epoxide 2 to form malonate alkoxide 3; Malonate alkoxide 3 reacts to form tetrahedral intermediate 4; Tetrahedral intermediate 4 collapses to form lactone 5; Lactone 5 reacts with aqueous base to form carboxylate 6; Carboxylate 6 reacts with aqueous acid to form the final product. Work out the mechanism on a separate sheet of paper, and then draw the structure of carboxylate 6.