Deuterium is selectively incorporated into the ring positions of-l-met
hylnaphthalene from gaseous deuterium, and the distribution of deuteri
um in the rings is essentially the same in the presence or absence of
coal. Incorporation is under kinetic control. Ring exchange appears to
be due to catalysis by the walls of the reactor. Incorporation in the
methyl position does not occur to an appreciable extent at 385 or 450
degrees C in the absence of coal, but extensive incorporation does oc
cur in the presence of coal. The pattern of ring substitution of deute
rium precludes, or places severe restrictions on, the role of hydrogen
shuttling by l-methylnaphthalene as an explanation for the observatio
n of higher coal conversion in this nondonor solvent than in a donor s
olvent, tetralin.