MATRIX INFRARED SPECTRUM AND BONDING IN THE MONOCHLOROMETHYL RADICAL
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Date
1970
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Ohio State University
Abstract
Simultaneous deposition of $CH_{2}ClX$ (X = F, Cl, Br, I) with atomic lithium or sodium at high dilution in argon on a CsI window maintained at $15^\circ K$ has produced the monochloromethyl free radical for infrared spectroscopic study. Vibrational assignments to $\nu_{2}$ (the symmetric C-Cl stretch), $\nu_{3}$ (the symmetric valance angle bend) and $\nu_{c}$ (the out of plane hydrogen bend) are supported by the reactions of lithium with $CHDCl_{2}$ and lithium or sodium with $CD_{2} Cl_{2}$. These assignments are further substantiated by normal coordinate calculations. The unusually high C-Cl force constant in $CH_{2}Cl$ (4.09=0.03 mdyn/\AA) indicates considerable stabilization of the C-Cl bond. Therefore, we suggest (p-p)$\pi$ bonding in $CH_{2}Cl$. The average calculated $F\alpha$ does not quantitatively account for the observed isotopic frequencies of $v_{6}$. However, a simple harmonicquartic potential function obtained from first order perturbation theory (V(O) = (1/2(1.83) ($\Delta$(O)$^{2}+ (10.7) (\Delta$O)$^{4}$)$\times 10^{-13}$ ergs) accurately determines the observed spectrum: this large positive quartic term is evidence for a planar radical.
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Author Institution: Department of Chemistry, University of Virginia