Under certain conditions, mixing furan with maleic anhydride in diethyl ether yields a crystalline solid wth a melting point of 114C. When melting point of this compound takes place; however, one can notice that the melt evolves a gas. If the melt is allowed to re-solidify, one finds that it no longer melts at 114C but instead melts at 56C. Provide an eplanation for what is taking place.