Study of the reaction of maleic anhydride with Illinois bituminous coal

Maleic anhydride reacted with Illinois No. 6 bituminous coal (mf) at 200 and 250 °C resulted in a 22.5 and 39.3% increase in weight, respectively, which was based on the benzene-insoluble residue. The carboxyl group content of this coal residue, after it had been refluxed with water and demineralized, was 2.01 meq g^?1 (459% increase) at 200 °C, and 2.74 meq g^?1 at 250 °C (626% increase). If one assumes an average molecular weight of 2000 for bituminous coal, these results correspond to approximately 2 mol dienophile reacting with each mol of coal. Carboxyl group content of the insoluble coal residue was determined by the barium acetate method.