Environmental Science & Engineering - www.esemag.com - September 2004
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Chemical catalysts may neutralize groundwater contaminants
Everything from the manufacture
of new materials to the creation
of modern medications
relies on chemicals known as
metal-based catalysts. Catalysts pack a
double punch - even as they greatly
increase the rate of chemical processes,
they regenerate so they can be used
again. Catalysts also can be designed
to break or make powerful chemical
bonds at one end of a molecule while
leaving the other end to sit quietly
inactive. For this reason, many
chemists, particularly inorganic
chemists who often study metals and
their reactivity, are on a continuing
quest for new catalysts.
At The Johns Hopkins University,
researchers have developed a new set
of molecules that has the potential to
catalyze a wide variety of chemical
reactions, including but not limited to
the clean-up of common but quite dangerous
groundwater pollutants called
organohalides. Scientists announced
their results in late August at the
American Chemical Society's annual
summer meeting, held in Philadelphia.
“Organohalides comprise a high
percentage of the priority pollutants as
registered by the EPA, so this is a pretty
important advance,” said David P.
Goldberg, associate professor in the
Department of Chemistry in the
Krieger School of Arts and Sciences at
Johns Hopkins. “In addition, our molecules
have the potential to catalyze a
number of other reactions important in
the synthesis of specialty chemicals
for industry.”
In the biological world, enzymes are
the catalysts which function inside
cells, and many enzymes depend on
metal held inside specially built organic
molecules called porphyrins. Using
these as a model, Goldberg’s team synthesized
a variation that changed the
properties of the reactive metal in the
center.
Called a “corrolazine”, the new ring
contains one less atom than other, better-
studied porphyrins. These molecules
are fascinating from a fundamental
perspective, Goldberg said. The tiny
change made in their structure imparts
some very different properties than the
same system found in nature, and may
allow scientists to catalyze reactions in
very different ways from their natural
counterparts.
“By studying these natural mimics,
we can learn a great deal about why
nature, actually evolution, made certain
choices in the design and development
of enzymes,” Goldberg said.
Though some of the molecules
being investigated by Goldberg's team
are important synthetic precursors that
can ultimately be used in making specialty
chemicals and pharmaceuticals,
other recent work in the group, spearheaded
by graduate students Joseph
Fox and David Capretto, has focused
on how to use the new catalysts to render the groundwater pollutants called
organohalides harmless by way of a
simple chemical reaction.
“Organohalides can be transformed
into safer compounds by breaking the
bonds between the halogen and carbon
atoms they contain,” Goldberg said.
Contact: www.jhv.edu.
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