Trichloroethylene reduction by outer-sphere electron transfer agents

Trichloroethylene (TCE) is an environmental contaminant that is degraded in natural and engineered systems by reduction. Several characteristic products are observed: cis-dichloroethylene, trans-dichloroethylene, vinyl chloride, dichloro-acetylene, chloroacetylene, ethylene, and acetylene. The product distribution is dependent on the reducing agent, which has led to the hypothesis that the distinguishing feature could be used as an indicator of mechanism. The reaction pathway for Vitamin B12, a common catalyst for reductive dechlorination, is unknown and both an inner-sphere and an outer-sphere mechanism have been proposed. TCE was reacted with well-defined outer-sphere reducing agents to establish the product distribution for this limiting reaction type. Preliminary results suggested that product ratios differ with each process and therefore might be used to determine which is dominant in natural systems. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA, 8/22-26/2004).