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# Isomeric effects in the gas-phase reactions of dichloroethene, C2H2Cl2, with a series of cations

Mikhailov, Victor A. and Parkes, M. A. and Tuckett, R. P. and Mayhew, C. A. (2006) Isomeric effects in the gas-phase reactions of dichloroethene, C2H2Cl2, with a series of cations. The Journal of Physical Chemistry A, 110 (17). pp. 5760-5771. ISSN 1089-5639

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URL of Published Version: http://dx.doi.org/10.1021/jp060093s

Identification Number/DOI: doi:10.1021/jp060093s

A study of the reactions of a series of gas-phase cations (NH$$_4^+$$, H$$_3$$O$$^+$$, SF$$_3^+$$, CF$$_3^+$$, CF$$^+$$, SF5$$^+$$, SF$$_2^+$$, SF$$^+$$, CF$$_2^+$$, SF$$_4^+$$, O$$_2^+$$, Xe$$^+$$, N$$_2$$O$$^+$$, CO$$_2^+$$, Kr$$^+$$, CO$$^+$$, N$$^+$$, N$$_2^+$$, Ar$$^+$$, F$$^+$$ and Ne$$^+$$) with the three structural isomers of dichloroethene, i.e. 1,1-C$$_2$$H$$_2$$Cl$$_2$$, cis-1,2-C$$_2$$H$$_2$$Cl$$_2$$ and trans-1,2-C$$_2$$H$$_2$$Cl$$_2$$ is reported. The recombination energy of these ions spans the range 4.7-21.6 eV. Reaction rate coefficients and product branching ratios have been measured at 298 K in a selected ion flow tube. Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental data. Thermochemistry and mass balance have been used to predict the most feasible neutral products. Threshold photoelectron-photoion coincidence spectra have also been obtained for the three isomers of C$$_2$$H$$_2$$Cl$$_2$$ with photon energies in the range 10-23 eV. The fragment ion branching ratios have been compared with those of the flow tube study to determine the importance of long-range charge transfer. A strong influence of the isomeric structure of dichloroethene on the products of ion-molecule reactions has been observed for H$$_3$$O$$^+$$, CF$$_3^+$$, and CF$$^+$$. For 1,1-C$$_2$$H$$_2$$Cl$$_2$$ the reaction with H$$_3$$O$$^+$$ proceeds at the collisional rate with the only ionic product being 1,1-C$$_2$$H$$_2$$Cl$$_2$$H$$^+$$. However, the same reaction yields two more ionic products in the case of cis-1,2- and trans-1,2-C$$_2$$H$$_2$$Cl$$_2$$, but only proceeds with 14 % and 18 % efficiency, respectively. The CF$$_3^+$$ reaction proceeds with 56-80 % efficiency, the only ionic product for 1,1-C$$_2$$H$$_2$$Cl$$_2$$ being C$$_2$$H$$_2$$Cl$$^+$$ formed via Cl- abstraction, whereas the only ionic product for both 1,2-isomers is CHCl$$_2^+$$ corresponding to a breaking of the C=C double bond. Less profound isomeric effects, but still resulting in different products for 1,1- and 1,2-C$$_2$$H$$_2$$Cl$$_2$$ isomers, have been found in the reactions of SF$$^+$$, CO$$_2^+$$, CO$$^+$$, N$$_2^+$$, and Ar$$^+$$. Although these five ions have recombination energies above the ionization energy of any of the C$$_2$$H$$_2$$Cl$$_2$$ isomers and hence the threshold for long-range charge transfer, the results suggest that the formation of a collision complex at short range between these ions and C$$_2$$H$$_2$$Cl$$_2$$ is responsible for the observed effects.

Type of Work: Article 2006 (Publication) Schools (1998 to 2008) > School of Chemical Sciences School of Chemistry, School of Physics Ion-Molecule Reactions, Selected Ion Flow Tube, TPEPICO, Charge Transfer QD ChemistryQC Physics University of Birmingham American Chemical Society 748 YES

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