Vacuum-ultraviolet (147 nm) photodecomposition of 1,1,2-trichloro-2,2-difluoroethane

Article abstract of DOI:10.1063/1.439525

The 147 nm photolysis of CF2ClCHCl2 has been investigated at 25 deg C as a function of reactant pressure, conversion, and nitric oxide as additive.In the absence of NO the observed reaction products are CF2CHCl, CF2CCl2, and the diastereomers of (CF2ClCHCl)2.At constant reactanr pressure the quantum yields of the olefin decrease with increasing conversion and there is a corresponding increase in the quantum yield of the C4 product.For fixed values of conversion the olefin quantum yields decrease with increasing reactant pressure and approach limiting values at ca. 100 Torr.The addition of NO completely suppresses the formation of the chlorofluorobutanes, while it enhances the olefin quantum yields at higher conversion.These observations are interpreted in terms of reactions of chlorine atoms which result either directly (by near simultaneous expulsion of two Cl atoms), or via the dissociation of an excited Cl2^* molecule produced by molecular elimination in the primary process.Chlorine atoms abstract hydrogen from the parent or add to the product olefins.These processes provide the principal source of halo-ethyl radicals in the system.The addition reaction leads to chemically activated radicals with a mean lifetime of τ ca. 0.8*10^-8 sec which is commensurate with RRKM-theory predictions.The addition of nitric oxide provides a competing channel for chlorine atom removal by way of their NO-catalyzed recombination.The functional dependence of the olefin quantum yields with conversion in the absence and presence of NO suggests that the major fraction of the principal product, CF2CHCl, derives directly from a primary process, while CF2CCl2 is formed via both, the molecular elimination of HCl and from radical precursors.The limiting quantum yields of CF2CHCl and CF2CCl2 are found to be φ₀ ca. 0.68 and φ₀' ca. 0.19, in the absence of NO, respectively, and φ_0,NO ca. 0.56 and φ_0,NO' ca. 0.087 in the presence of NO.The extinction coefficient for CF2ClCHCl2 at 147 nm and 25 deg C has been determined: ε = (1/PL)ln(I₀/I_t) = 404 +/- 40 atm^-1cm^-1.

Full text of DOI:10.1063/1.439525

Vacuum–ultraviolet (147 nm) photodecomposition of 1,1,2trichloro2,2difluoroethane
T. Yano and E. TschuikowRoux
Citation: The Journal of Chemical Physics 72, 3401 (1980); doi: 10.1063/1.439525
View online: http://dx.doi.org/10.1063/1.439525
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/72/5?ver=pdfcov
Published by the AIP Publishing
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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.18.123.11 On: Sat, 20 Dec 2014 18:23:43