STRUCTURAL INVESTIGATION OF COAL-TAR PITCHES AND COAL EXTRACTS BY C-13 NMR-SPECTROSCOPY

The structural composition of hard and brown coal tar pitches and coal extracts is analysed by 13C n.m.r. spectroscopy on the basis of the chemical-shift data for selected model compounds. For hard-coal-tar pitch, the high aromaticity is confirmed, the predominance of alternant hydrocarbon building blocks established, and the minute aliphatic resonances assigned to definite types of methyl groups and methylene linkages. In brown-coal-tar pitch, long straight-chain alkanes are identified as the major constituents. For three coal extracts obtained by different technical processes, the similar 13C spectral patterns demonstrate their analogous composition. The most striking feature in these spectra is an aliphatic resonance at 30 ppm which is assigned to a structural principle of the dihydrophenanthrene type, in accordance with a modified Given model for the structure of coal. © 1978.