The conformational equilibria and the IR and Raman spectra of 2‐(choromethyl)‐2‐methyl‐1,3‐dichloropropane

Abstract

AbstractThe infrared spectra of 2‐chloromethyl‐2‐methyl‐1,3‐dichloropropane in several phases, including the pure liquid, as a solute and as an amorphous and crystalline solid at 80 K and under pressure (2–30 kbar), have been recorded. Raman spectra of the neat liquid and of the plastic and anisotropic crystalline phases were obtained at various temperatures.A large number of IR and Raman bands present in the neat liquid, in solution and in the plastic crystalline phase vanished in the low‐temperature and in the high‐pressure crystal spectra. Among seven possible conformers, three (having symmetries C1, C8 and C3) have no 1,3‐parallel CCI bonds and are present in the liquid, in solution and in the plastic phase. In the anisotropic crystal, only the C1 conformer was present. A phase transition between the plastic and anisotropic crystal occurred at 253 K. ΔH0 values between the most stable conformers Cs and C1 were 5±1 and 3±1 kJ mol−1 K−1 in the plastic phase and in the liquid phase, respectively.A force constant calculation for the C1, Cs and C3 conformers and for various conformers of other halogenated neopentanes (a total of 11 conformer molecules) was carried out with the overlay technique. A 41‐parameter force field was adjusted to more than 280 observed frequencies, giving very satisfactory agreement.The spectra were interpreted in terms of conformers of C1, Cs and C3 symmetry.