The study of high-severity liquefaction carried out at UNDERC using Big Brown Texas lignite demonstrated the viability of natural abundance /sup 2/H NMR spectroscopy for the study of coal conversion reactions, particularly H-transfer chemistry. Several observations were made that indicated that further investigations in this area would be fruitful. They are: (1) differences in natural abundance /sup 2/H NMR distributions resulted from differences in the processing history of the samples; and (2) the addition of small amounts of H-donor to a liquefaction reaction changed the natural abundance /sup 2/H NMR distribution with respect to an identical run without added donor. The /sup 1/H and /sup 13/C distribution were unchanged. These observations mean that the history of a sample could be compared with that of another sample and that the H-donor history may be deduced from the comparative data. Some mechanistic and kinetic information was obtained from high-severity liquefaction reactions with labeled syngas (/sup 2/H/sub 2//CO and H/sub 2///sup 13/CO). Tests made with /sup 2/H/sub 2//CO showed product incorporation of /sup 2/H to be greater than 270 times the natural abundance level as determined by standard addition /sup 2/H NMR spectroscopy and the /sup 2/H distribution was not the same as in the unlabeled test. /sup 2/H entered all fractions of the product during the test including the distillate alkanes, phenols and polars, H/sub 2/O, and soluble vacuum bottoms. Polars and H/sub 2/O were the most enriched fractions, due to relatively easy H-exchange. There was a distinct isotope effect on the yield as processing with /sup 2/H/sub 2//CO resulted in decreased conversion to THF solubles when compared with the identical test with /sup 1/H/sub 2//CO. 22 refs., 2 figs., 7 tabs.