Issue 3, 2020

Reduction of 1,2,3-trichloropropane (TCP): pathways and mechanisms from computational chemistry calculations

Abstract

The characteristic pathway for degradation of halogenated aliphatic compounds in groundwater or other environments with relatively anoxic and/or reducing conditions is reductive dechlorination. For 1,2-dihalocarbons, reductive dechlorination can include hydrogenolysis and dehydrohalogenation, the relative significance of which depends on various structural and energetic factors. To better understand how these factors influence the degradation rates and products of the lesser halogenated hydrocarbons (in contrast to the widely studied per-halogenated hydrocarbons, like trichloroethylene and carbon tetrachloride), density functional theory calculations were performed to compare all of the possible pathways for reduction and elimination of 1,2,3-trichloropropane (TCP). The results showed that free energies of each species and reaction step are similar for all levels of theory, although B3LYP differed from the others. In all cases, the reaction coordinate diagrams suggest that β-elimination of TCP to allyl chloride followed by hydrogenolysis to propene is the thermodynamically favored pathway. This result is consistent with experimental results obtained using TCP, 1,2-dichloropropane, and 1,3-dichloropropane in batch experiments with zerovalent zinc (Zn0, ZVI) as a reductant.

Graphical abstract: Reduction of 1,2,3-trichloropropane (TCP): pathways and mechanisms from computational chemistry calculations

Supplementary files

Article information

Article type
Paper
Submitted
01 Dec 2019
Accepted
22 Jan 2020
First published
23 Jan 2020
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Processes Impacts, 2020,22, 606-616

Reduction of 1,2,3-trichloropropane (TCP): pathways and mechanisms from computational chemistry calculations

T. L. Torralba-Sanchez, E. J. Bylaska, A. J. Salter-Blanc, D. E. Meisenheimer, M. A. Lyon and P. G. Tratnyek, Environ. Sci.: Processes Impacts, 2020, 22, 606 DOI: 10.1039/C9EM00557A

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