Ab initio electronic structure study of one-electron reduction of polychlorinated ethylenes

Eric J. Bylaska, Michel Dupuis, Paul Tratnyek

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Polychlorethylene radicals, anions, and radical anions are potential intermediates in the reduction of polychlorinated ethylenes (C 2C1 4, C 2HCl 3) trans-C 2H 2Cl 2, cis-C 2H 2Cl 2, 1,1-C 2H 2Cl 2, C 2H 3Cl). Ab initio electronic structure methods were used to calculate the thermochemical properties, ΔH f°(298.15 K), S°(298.15 K,1 bar), and ΔG S(298.15 K, l bar) of 37 different polychloroethylenyl radicals, anions, and radical anion complexes, C 2H yCl 3-y C 2H yCl 3-y, -, and C 2H yCl 4-y for y = 0-3, for the purpose of characterizing reduction mechanisms of polychlorinated ethylenes. In this study, 8 radicals, 7 anions, and 22 radical anions were found to have stable structures, i.e., minima on the potential energy surfaces. This multitude of isomers for C 2H y,Cl 4-y radical anion complexes are π*, σ*, and -H⋯CI -structures. Several stable π* radical anionic structures were obtained for the first time through the use of restricted open-shell theories. On the basis of the calculated thermochemical estimates, the overall reaction energetics (in the gas phase and aqueous phase) for several mechanisms of the first electron reduction of the polychlorinated ethylenes were determined. In almost all of the gas-phase reactions, the thermodynamically most favorable pathways involve -H⋯Cl - complexes of the C 2H yCl 4-y radical anion, in which a chloride ion is loosely bound to a hydrogen of a C 2H xCl 2-x radical. The exception is for C 2Cl 4, in which the most favorable anionic structure is a loose σ* radical anion complex, with a nearly iso-energetic π* radical anion. Solvation significantly changes the product energetics with the thermodynamically most favorable pathway leading to C 2H yCl 3-y + Cl -. The results suggest that a higher degree of chlorination favors reduction, and that reduction pathways involving the C 2H yCl 3-y - anions are high energy pathways.

Original languageEnglish (US)
Pages (from-to)5905-5916
Number of pages12
JournalJournal of Physical Chemistry A
Volume109
Issue number26
DOIs
StatePublished - Jul 7 2005

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Ethylenes
Electronic structure
Anions
ethylene
electronic structure
anions
Electrons
electrons
Gases
vapor phases
Potential energy surfaces
shell theory
thermochemical properties
chlorination
Chlorination
Solvation
Human computer interaction
Isomers

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Ab initio electronic structure study of one-electron reduction of polychlorinated ethylenes. / Bylaska, Eric J.; Dupuis, Michel; Tratnyek, Paul.

In: Journal of Physical Chemistry A, Vol. 109, No. 26, 07.07.2005, p. 5905-5916.

Research output: Contribution to journalArticle

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title = "Ab initio electronic structure study of one-electron reduction of polychlorinated ethylenes",
abstract = "Polychlorethylene radicals, anions, and radical anions are potential intermediates in the reduction of polychlorinated ethylenes (C 2C1 4, C 2HCl 3) trans-C 2H 2Cl 2, cis-C 2H 2Cl 2, 1,1-C 2H 2Cl 2, C 2H 3Cl). Ab initio electronic structure methods were used to calculate the thermochemical properties, ΔH f°(298.15 K), S°(298.15 K,1 bar), and ΔG S(298.15 K, l bar) of 37 different polychloroethylenyl radicals, anions, and radical anion complexes, C 2H yCl 3-y C 2H yCl 3-y, -, and C 2H yCl 4-y for y = 0-3, for the purpose of characterizing reduction mechanisms of polychlorinated ethylenes. In this study, 8 radicals, 7 anions, and 22 radical anions were found to have stable structures, i.e., minima on the potential energy surfaces. This multitude of isomers for C 2H y,Cl 4-y radical anion complexes are π*, σ*, and -H⋯CI -structures. Several stable π* radical anionic structures were obtained for the first time through the use of restricted open-shell theories. On the basis of the calculated thermochemical estimates, the overall reaction energetics (in the gas phase and aqueous phase) for several mechanisms of the first electron reduction of the polychlorinated ethylenes were determined. In almost all of the gas-phase reactions, the thermodynamically most favorable pathways involve -H⋯Cl - complexes of the C 2H yCl 4-y • radical anion, in which a chloride ion is loosely bound to a hydrogen of a C 2H xCl 2-x • radical. The exception is for C 2Cl 4, in which the most favorable anionic structure is a loose σ* radical anion complex, with a nearly iso-energetic π* radical anion. Solvation significantly changes the product energetics with the thermodynamically most favorable pathway leading to C 2H yCl 3-y • + Cl -. The results suggest that a higher degree of chlorination favors reduction, and that reduction pathways involving the C 2H yCl 3-y - anions are high energy pathways.",
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N2 - Polychlorethylene radicals, anions, and radical anions are potential intermediates in the reduction of polychlorinated ethylenes (C 2C1 4, C 2HCl 3) trans-C 2H 2Cl 2, cis-C 2H 2Cl 2, 1,1-C 2H 2Cl 2, C 2H 3Cl). Ab initio electronic structure methods were used to calculate the thermochemical properties, ΔH f°(298.15 K), S°(298.15 K,1 bar), and ΔG S(298.15 K, l bar) of 37 different polychloroethylenyl radicals, anions, and radical anion complexes, C 2H yCl 3-y C 2H yCl 3-y, -, and C 2H yCl 4-y for y = 0-3, for the purpose of characterizing reduction mechanisms of polychlorinated ethylenes. In this study, 8 radicals, 7 anions, and 22 radical anions were found to have stable structures, i.e., minima on the potential energy surfaces. This multitude of isomers for C 2H y,Cl 4-y radical anion complexes are π*, σ*, and -H⋯CI -structures. Several stable π* radical anionic structures were obtained for the first time through the use of restricted open-shell theories. On the basis of the calculated thermochemical estimates, the overall reaction energetics (in the gas phase and aqueous phase) for several mechanisms of the first electron reduction of the polychlorinated ethylenes were determined. In almost all of the gas-phase reactions, the thermodynamically most favorable pathways involve -H⋯Cl - complexes of the C 2H yCl 4-y • radical anion, in which a chloride ion is loosely bound to a hydrogen of a C 2H xCl 2-x • radical. The exception is for C 2Cl 4, in which the most favorable anionic structure is a loose σ* radical anion complex, with a nearly iso-energetic π* radical anion. Solvation significantly changes the product energetics with the thermodynamically most favorable pathway leading to C 2H yCl 3-y • + Cl -. The results suggest that a higher degree of chlorination favors reduction, and that reduction pathways involving the C 2H yCl 3-y - anions are high energy pathways.

AB - Polychlorethylene radicals, anions, and radical anions are potential intermediates in the reduction of polychlorinated ethylenes (C 2C1 4, C 2HCl 3) trans-C 2H 2Cl 2, cis-C 2H 2Cl 2, 1,1-C 2H 2Cl 2, C 2H 3Cl). Ab initio electronic structure methods were used to calculate the thermochemical properties, ΔH f°(298.15 K), S°(298.15 K,1 bar), and ΔG S(298.15 K, l bar) of 37 different polychloroethylenyl radicals, anions, and radical anion complexes, C 2H yCl 3-y C 2H yCl 3-y, -, and C 2H yCl 4-y for y = 0-3, for the purpose of characterizing reduction mechanisms of polychlorinated ethylenes. In this study, 8 radicals, 7 anions, and 22 radical anions were found to have stable structures, i.e., minima on the potential energy surfaces. This multitude of isomers for C 2H y,Cl 4-y radical anion complexes are π*, σ*, and -H⋯CI -structures. Several stable π* radical anionic structures were obtained for the first time through the use of restricted open-shell theories. On the basis of the calculated thermochemical estimates, the overall reaction energetics (in the gas phase and aqueous phase) for several mechanisms of the first electron reduction of the polychlorinated ethylenes were determined. In almost all of the gas-phase reactions, the thermodynamically most favorable pathways involve -H⋯Cl - complexes of the C 2H yCl 4-y • radical anion, in which a chloride ion is loosely bound to a hydrogen of a C 2H xCl 2-x • radical. The exception is for C 2Cl 4, in which the most favorable anionic structure is a loose σ* radical anion complex, with a nearly iso-energetic π* radical anion. Solvation significantly changes the product energetics with the thermodynamically most favorable pathway leading to C 2H yCl 3-y • + Cl -. The results suggest that a higher degree of chlorination favors reduction, and that reduction pathways involving the C 2H yCl 3-y - anions are high energy pathways.

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