Vibrational Intensities in Halogenated Methanes. I. Methylene Chloride

Abstract

The absolute infrared absorption intensities of four fundamental bands in CH₂Cl₂ have been measured in the vapor state. The intensities that have been observed are $$\begin{array}{c}{A}_6\mathrm{\hspace{0.17em}(}\mathrm{CH\; stretching}{\text{)=48.0×10}}^{10}\hspace{0.17em}\mathrm{cycles}/\mathrm{sec\; at\; NTP}\\ A_7\mathrm{\hspace{0.17em}(}\mathrm{CH\; rocking}{\text{)=13.0×10}}^0\hspace{0.17em}\mathrm{cycles}/\mathrm{sec\; at\; NTP}\\ A_8\mathrm{\hspace{0.17em}(}\mathrm{CCl\; stretching}{\text{)=1420.0×10}}^{10}\hspace{0.17em}\mathrm{cycles}/\mathrm{sec\; at\; NTP}\\ A_9\mathrm{\hspace{0.17em}(}\mathrm{CCl\; rocking}{\text{)=375.0×10}}^{10}\hspace{0.17em}\mathrm{cycles}/\mathrm{sec\; at\; NTP}.\end{array}$$ These data indicate that the bond moments and bond derivatives are $$\begin{array}{c}{\mu }_{\mathrm{CH}}{\text{=+0.45×10}}^{\text{−18}}\hspace{0.17em}\mathrm{esu}\\ {\mu }_{\mathrm{CCl}}{\text{=−0.95×10}}^{\text{−18}}\mathrm{esu}\\ {\mathrm{\partial \mu }}_{\mathrm{CH}}{\mathrm{/\partial r}}_{\mathrm{CH}}{\text{=+0.3×10}}^{\text{−10}}\hspace{0.17em}\mathrm{esu\; or}{\text{\hspace{0.17em}−0.2×10}}^{\text{−10}}\hspace{0.17em}\mathrm{esu}\\ {\mathrm{\partial \mu }}_{\mathrm{CCl}}{\mathrm{/\partial r}}_{\mathrm{CCl}}{\text{=+3.7×10}}^{\text{−10}}\hspace{0.17em}\mathrm{esu}.\end{array}$$ It was not possible to resolve the ambiguity in signs that lead to the alternate values of ∂μ_CH/∂r_CH.