Chemical structure of tar-sand bitumens by 13C and 1H n.m.r. spectroscopic methods

¹H and ¹³C n.m.r. spectra of Athabasca, Cold Lake and Orinoco tar-sand bitumens, their columnchromatographed fractions, their vacuum distillates, their vacuum residues and the columnchromatographed fractions of the vacuum residues were determined to investigate the average molecular structures of these materials. The most probable average structural parameters were calculated without making any assumptions, and average structural models for the Athabasca series are proposed. Compared with corresponding petroleum fractions, tar-sand bitumens contain shorter, paraffinic straight-chains and are abundant in alicyclic carbon atoms. This trend is more marked in the saturate fractions or vacuum distillates. The vacuum residues of tar-sand bitumens contain relatively longer, paraffinic straight-chains than the original bitumens.