Stephen E. Stein

Henry H. Storch Award in Fuel Chemistry
sponsored by Exxon Research & Engineering Co.

STEPHEN E. STEIN has shown
how fundamental principles of predictive
thermochemistry and kinetics
and model compound studies can
be used to understand complex coal
reactions. In particular, his pioneering
research has provided a general
framework on which to view coal
conversion chemistry and to build
mechanistic models.
In one set of theoretical studies,
Stein, a research chemist in the
chemical kinetics division of the National
Institute of Standards & Technology
(NIST), applied the Hûckel
molecular orbital theory to homologous
series of benzenoid polycyclic
aromatic hydrocarbons (PAHs). This
work showed that reactivity depends
almost solely on the chemical structures
near the reaction site, leading to
"an impressive simplification/' as
one colleague puts it, of the problem
of reactions of complex mixtures of
PAHs. In turn, it enables the examination
of possible chemical mechanisms
for coal gasification. In other
such studies, Stein organized the
types of reactions and classes of free
radicals of probable importance in
thermal coal chemistry.
In experimental work, Stein and
his coworkers measured rate constants
needed for predicting the behavior
of reacting systems of aromatic
and polycylic aromatic molecules.
Rate constants for radical disproportionation,
for instance, were measured
for the first time for hydroaromatic
radicals and an unexpected dependence
on radical structure was
found. More recently, Stein determined
the dissociation rates of a
large number of substituted anisoles
and the effects of various substituents
on bond strengths.
The result of his theoretical and
experimental work has been a much
better understanding of carbon
growth and Η-transfer reactions.
And it has provided a scientific basis
for the idea of active sites as well as
a method for estimating energies of
reactions at the edges of large PAHs.
Stein received a B.S. degree in
chemistry from the University of

Rochester in 1969, and a Ph.D. degree
in physical chemistry from the
University of Washington, Seattle,
in 1974. He did postdoctoral work
and was a research chemist at Stanford
Research Institute from 1974 to
1976, and it was during this period
that he began his research in coal
chemistry. He joined the faculty at
West Virginia University in 1976
and moved to NIST in 1982.
Stein has more than 50 publications
to his credit. He served on the
editoral board of the International
Journal of Chemical Kinetics from 1976
to 1987. He has been a consultant to
Union Carbide and Exxon.

30 October 28, 1991 C&EN