Matrix-Isolation Studies of the Infrared Spectra of the Free Radicals CCl3 and CBr3

CCl₃ has been stabilized both by the reaction of lithium atoms with CCl₄ in an argon matrix at 20°K and by the vacuum‐ultraviolet photolysis of HCCl₃ or of DCCl₃ in an argon or a nitrogen matrix at 14°K. The analogous techniques have been found to lead to the stabilization of CBr₃. The product spectra obtained in the lithium‐atom experiments are considerably simpler than those obtained in the previous studies of the reaction of lithium atoms with matrix‐isolated CX₄. In the vacuum‐ultraviolet photolysis experiments, DCCl₂, HCBr₂, and CBr₂ have also been observed. The absorption frequencies and contours obtained for ${\nu }_3$ of CCl₃ and of CBr₃ are independent of the method used to produce these species, suggesting that lithium atoms and their reaction products do not appreciably perturb the degenerate stretching mode of either CCl₃ or CBr₃. Despite yields of these species comparable to those previously reported, absorptions at 674 and at 582 cm⁻¹, previously attributed to ${\nu }_1$ of CCl₃ and CBr₃, respectively, are completely missing from the present experiments. No other absorption attributable to ${\nu }_1$ of either species has been detected. It is concluded that a pyramidal ${\mathrm{(C}}_{\text{3υ}})$ structure for CCl₃ and for CBr₃ has not been established.