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Hydrogen Atoms Transfer In Same Way As Electrons Do

During the last 40 years, chemists have developed an understanding of how an electron transfers from one group to another to create new compounds.

Now a team of University of Washington chemists has found that the same ideas apply to transferring a hydrogen atom -- an electron and a proton -- together. That understanding could prove important to scientists trying to devise new classes of chemical reactions.

"What we've shown is that one approach works for a wide range of hydrogen atom transfer reactions, including those involving metals and purely organic reactions. The processes are the same," said James Mayer, a UW chemistry professor who heads the research team.

For industry, hydrogen transfer reactions are key to many processes, from the creation of synthetic materials such as nylon to keeping plastic and paint from breaking down when exposed to light. Hydrogen transfer also holds deep interest for biochemists since it is a key step in a variety of enzyme processes and in the function of antioxidants such as vitamins C and E. There even are potential applications in areas such as environmental chemistry, Mayer said.

Research in Mayer's laboratory that led to the deeper understanding of hydrogen transfer is described in a paper published in today's edition of Science. Other authors include Justine Roth, who earned her doctorate at the UW and now is a postdoctoral researcher at the University of California, Berkeley; Jeffrey Yoder, a UW chemistry research associate; and Tae-Jin Won, an assistant professor at Changwon National University in South Korea who was on leave at the UW during the time of the research.

Understanding how a hydrogen atom can leave one molecular group for another is key to creating new compounds. The process occurs at different rates for different compounds. For instance, the nature of the bond between the two atoms makes it easy to transfer hydrogen to or from oxygen, while hydrogen linked to carbon is much more difficult to transfer, and more energy is required, Mayer said.

"These kinds of chemical reactions can be thought of as trying to pipe water over the mountains," he said. "The pipe goes over a pass and down to a lower spot on the other side. The farther down you go the more gravity will pull the water along and the faster the water -- or in this case the chemical reaction -- flows.

"You also will get more flow if you use a larger pipe -- it is naturally easier to push a lot of water through a larger pipe. Our studies show how hydrogen atom transfer is affected both by the amount of push and the inherent properties of the materials."

As scientists achieve a better understanding of how these chemical transfers take place, they will have a clearer idea of what is required to devise new classes of chemical reactions, which ultimately will lead to development of new compounds. It also can give chemists for manufacturing companies a clearer understanding of what's happening as they combine chemicals to produce materials for their companies' products.

"Having a better understanding, companies can make their products in cleaner, more efficient ways," Mayer said.

Developing that kind of understanding does not lead immediately to breakthrough new products, he said, but in the long run it should help in knowing the best way to make or improve a product, or to manufacture a new product.

"We have shown how you have to think about the problem," he said. "This is an important way to move the science forward."

Mayer's work was paid for by a grant from the National Institutes of Health. - By Vince Stricherz

[Contact: James Mayer, Vince Stricherz]






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