Noncovalent Interactions in High-Rank Coals

Abstract

The adducts formed by reacting maleic anhydride and bituminous coals of varying rank have been prepared. The adducts contain between 16% and 19% maleic anhydride. The extractabilities of the coals and their adducts have been measured in pyridine and THF. For coals having less than 88% C (dmmf), the extractabilities of the coal and its maleic anhydride adduct are the same. The adducts of coals containing more than 90% C are much more extractable than the starting coal is. It is suggested that the coals having more than 90% C are associated by London dispersion interactions (“stacking interactions”) between PNA systems. These interactions are not important to the extractability of lower rank coals because either the size or the population of the PNA systems is insufficient. © 1987, American Chemical Society. All rights reserved.