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J . A m . Chem. Soc. 1984, 106, 299-303
Photoelectron Spectroscopic Study of the Ground States of CH2C1+,CHC12+,and CHFC1' Lester Andrews,* John M. Dyke, Neville Jonathan, Noureddine Keddar, and Alan Morris Contribution f r o m the Department of Chemistry, The University, Southampton, SO9 5 N H , U.K. Received August 15, 1983
Abstract: Reactions of chloromethanes with fluorine atoms produced the CH2C1,CHC12,and C H F C l free radicals for observation of structured first photoelectron bands. These bands a t 8.87, 8.54, and 9.16 f 0.01 eV vertical ionization energies, respectively, exhibited 1040 f 30, 860 f 30, and 920 f 40 cm-I vibronic intervals that are due to symmetric C-C1 stretching fundamentals in the ground states of the CH2CI+,CHC12+,and CHFCl' cations. The observed fundamentals a r e substantially higher than corresponding values for the ground electronic states of the neutral radicals, which indicates a substantial increase in net C-CI bonding in the cations as compared to the free radicals.
Introduction Photoelectron spectroscopy has been generally employed t o study stable molecules and low-lying electronic states of t h e corresponding cations.',* Although free radicals require special methods for preparation, these species are interesting subjects for photoelectron spectroscopic investigation since t h e cations formed on ionization may have different bonding and structure from t h e neutral free radicals. Hydrogen a t o m abstraction by fluorine a t o m s from suitable precursors has proven t o be a n effective method for preparing free radicals for photoelectron spectroscopic s t ~ d y . ~T- h~i s paper reports such a study of t h e ground states of C H 2 C l + , CHCl2+,and CHFCI' produced by ionization of the corresponding free radicals; preliminary photoelectron spectra of t h e CH,CI free radical have been communicated in a n earlier letter.6 Only a few direct observations of chloromethyl free radicals have been reported, although these radicals have been proposed as reaction intermediate^.'-^ The infrared s p e c t r u m of CH2C1 in solid argon provided evidence for a planar radical with some (C2p
