Mechanistic Studies of Vitamin B12 Mediated DechlorinationEPA Grant Number: U915562
Title: Mechanistic Studies of Vitamin B12 Mediated Dechlorination
Investigators: Shey, Justin
Institution: University of Illinois at Urbana-Champaign
EPA Project Officer: Packard, Benjamin H
Project Period: June 1, 1999 through June 1, 2002
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1999) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Chemistry and Materials Science
The objective of this research project is to elucidate the chemical mechanism by which certain enzymatic and non-enzymatic systems dechlorinate perchloroethylene (PCE) and trichloroethylene (TCE).
To understand the mechanism of non-enzymatic dechlorination, the dechlorination of two radical probes (cis and trans-[2-trichlorovinyl-cyclopropyl]-benzene) will be synthesized and studied, and a stopped-flow UV-vis apparatus will be utilized. With the radical probes, the investigators intend to "trap" any radical that forms alpha to the cyclopropane ring during the dechlorination process. If the major products are opened using the ring, it would support a mechanism in which radicals are involved in the non-enzymatic dechlorination process. Because 2-propanol is a reliable hydrogen atom donor, the dechlorination of the trans radical probe also will be performed in deuterated water with 2-propan(ol-d) as well as water with 2-propan-2-d-ol. If the deuterated water system provides more deuterated products, it would suggest that the product obtains the hydrogen as a proton. Likewise, if the water system results in more deuterated products, it would support the hypothesis that the product obtains the hydrogen as a hydrogen atom. The stopped-flow methodology allows monitoring of the oxidation states of cobalt on the sub-second time scale. Because the three different oxidation states of cobalt in cobalamin offer very distinct UV-vis spectra, the mechanism of dechlorination could be followed by observing the cobalamin during the reaction. With the stopped-flow apparatus, activation parameters for these reactions also could be obtained.
If the mechanism and rate limiting step(s) of dechlorination can be elucidated for the abiotic system, rational design and synthesis of remediation systems that are inexpensive and more effective can be realized.