Environmental Science & Technology 2007-11-01

Evidence for a radical mechanism of the dechlorination of chlorinated propenes mediated by the tetrachloroethene reductive dehalogenase of Sulfurospirillum muftivorans.

Roland P H Schmitz, Julia Wolf, Andreas Habel, Anke Neumann, Kerstin Ploss, Ales Svatos, Wilhelm Boland, Gabriele Diekert

Index: Environ. Sci. Technol. 41(21) , 7370-5, (2007)

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Abstract

The reductive dehalogenation of chlorinated propenes was studied with the tetrachloroethene reductive dehalogenase purified from Sulfurospirillum multivorans to obtain indications for a radical mechanism of this reaction. When reduced methyl viologen (MV), which is a radical cation, was applied as electron donor for the reduction of different chloropropenes, a significant part of MV could not be rereduced with Ti(III) citrate, indicating that a part of the MV was consumed in a side reaction. Mass spectrometric analysis of assays with MV as electron donor revealed the formation of side products, the masses of which might account for the formation of adducts from a chloropropenyl radical and reduced methyl viologen. With Ti(III) citrate as sole electron donor, 2,3-dichloropropene was reduced and as a side product, 2,5-dichloro-1,5-hexadiene was formed demonstrating that the reductive dechlorination of 2,3-dichloropropene proceeds via a radical reaction mechanism. The results support different dehalogenation mechanisms forthe reductive dechlorination of chloropropenes and halogenated ethenes.