Infrared Spectrum of the Trichloromethyl Radical in Solid Argon

Abstract

The primary products of the reaction of lithium atoms and carbon tetrachloride in solid argon at 15°K are lithium chloride and the trichloromethyl radical, which are identified by infrared spectral studies. Natural chlorine isotopes, carbon 13 and bromine substitution, and loss of CCl₃ absorptions with attendant growth of absorptions due to C₂Cl₆ on sample warming verify the molecular identity. Assignments to the carbon–chlorine stretching vibrations ${\nu }_1\text{\hspace{0.17em}=\hspace{0.17em}674}$ and ${\nu }_3\text{\hspace{0.17em}=\hspace{0.17em}898}{\mathrm{cm}}^{\text{−1}}$ are supported by normal coordinate calculations, and the weak bending modes ${\nu }_2$ and ${\nu }_4$ were not detected. The stretching force constants $F_{\tau }\text{\hspace{0.17em}=\hspace{0.17em}3.83}\mathrm{mdyn}\mathrm{\hspace{0.17em}/\hspace{0.17em}\AA }$ and $F_{\mathrm{\tau \tau }}\text{\hspace{0.17em}=\hspace{0.17em}0.43}\mathrm{mdyn}\mathrm{\hspace{0.17em}/\hspace{0.17em}\AA }$ are compared with those of other chlorocarbons and BCl₃ This comparison supports proposed resonance stabilization of the trichloromethyl radical.