Knowledge Bank

The reaction of chlorine atoms with ethylene and two of its deuterium isotopomers in solid $para$-hydrogen ($p$-H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$) matrices at 3 K has been studied using infrared spectroscopy. Irradiation at 365 nm of a co-deposited mixture of Cl$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$, C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$H$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$, and $p$-H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ at 3 K produces a series of new lines in the infrared spectrum. Several of the new lines are readily assigned to the gauche and trans conformers of 1,2-dichloroethane (CH$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ClCH$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Cl) resulting from the addition of two Cl atoms to C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$H$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$. Of the remaining lines, a strong line at 664 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ and three weaker lines at 562, 1070, and 1228 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ are concluded to be due to a single carrier based on their behavior upon subsequent annealing to 4.5 K and irradiation at 254 and 214 nm. When the positions and intensities of these lines are compared to the MP2/aug-cc-pVDZ predicted vibrational spectra of the possible species that could result from the addition and abstraction reactions of one Cl atom with C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$H$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$, 10842 (2000)}, the best agreement is found with the 2-chloroethyl radical ($\cdot$CH$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CH$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Cl). In order to confirm this assignment, isotopic experiments were performed with C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$D$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$ and t-C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$D$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ and the corresponding infrared bands due to the deuterium isotopomers of this radical ($\cdot$CD$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CD$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Cl and $\cdot$CHDCHDCl) have been observed. A final set of experiments were performed following irradiation of the Cl$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$/C$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$H$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$/$p$-H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ mixture at 365 nm, in which the matrix was irradiated with filtered infrared light from a globar source, which has been shown to induce a reaction between isolated Cl atoms and matrix H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ to produce HCl and H atoms, 3124 (2006)}. In our experiments, the major products observed were HCl and ethyl chloride (CH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$CH$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$Cl) and the possible mechanism of the formation of ethyl chloride will be discussed.