Mixing furan (Problem 13.45) with maleic anhydride in diethyl ether yields a crystalline solid with a melting point of 125(C. When melting of this compound takes place, however, one can notice that the melt evolves a gas. If the melt is allowed to resolidify, one finds that it no longer melts at 125(C but instead it melts at 56(C. Consult an appropriate chemistry handbook and provide an explanation for what is taking place.