Infrared data were obtained for chloromethylphosphorous dichloride, chloromethylphosphonic dichloride (also Raman data), and chloromethylthiophosphonic dichloride over the region 45–3800 cm<sup>−1</sup>. Infrared data were also obtained for bromomethylphosphonic dibromide in the region 300–3800 cm<sup>−1</sup>. Infrared spectra for these compounds were recorded at different temperatures, and show that the pentavalent compounds exist as rotational isomers at room temperature. A previous study of chloromethylphosphonic dichloride and chloromethylthiophosphonic dichloride has established that these two compounds exist as rotational isomers, but the present study gives additional significant information. The infrared spectrum for methylphosphonic dichloride in the region 45–600 cm<sup>−1</sup> has been recorded for purpose of comparison with the ClCH<sub>2</sub>–P series. No spectral evidence was observed for the P–CH<sub>3</sub> torsion vibration in methylphosphonic dichloride.
R. A. Nyquist, "Vibrational Spectroscopic Studies of Organophosphorus Compounds: ClCH2–PCl2, XCH2,–P(=O)X2, and ClCH2–P(=S)Cl2," Appl. Spectrosc. 22, 452-459 (1968)