Relationships between hydrogen donor abilities and chemical structure of aromatic compounds in terms of coal liquefaction

To obtain fundamental information about hydrogen transfer, the relationships between hydrogen donor ability and chemical structure of model compounds representing donor solvents is studied using gas chromatography,¹H n.m.r. and computing calculation methods. The order of the model compounds in terms of the ability as donor solvent to release hydrogen is: decalin < tetralin < 1,2-dihydronaphthalene < < 1,4-dihydronaphthalene. This trend closely correlates with the difference in binding energies of the hydroaromatic compounds and their radicals, determined by intermediate neglect of differential overlap (INDO) calculation. Electron spin resonance spectroscopy (e.s.r.) confirms that radical species are created after heat-treatment of the donor compounds. The ability of model compounds representing coal to accept hydrogen is assessed from a comparison of the¹H n.m.r. spectra. It is established that donor and acceptor efficacies are dependent upon chemical structure.