Vibration Spectra and Rotational Isomerism of Chain Molecules. VI. 2-Chloro-, 2-Bromo-, and 2-Iodoethyl Methyl Ethers

The Raman and infrared spectra of 2-chloro-, 2-bromo, and 2-iodoethyl methyl ethers, CH3OCH2CH2X (X=Cl, Br, and I), were measured for the liquid, glassy, and crystalline states. The gaseous-state spectra of the chloride were also measured. The vibrational frequencies of these molecules were calculated by the use of the force constants transferred directly from unbranched ethers and alkyl halides. The rotational isomerism was studied and the following conclusions were obtained. (1) In the crystalline state, the molecule takes the form having the trans conformation about the CO–CC axis and the gauche conformation about the OC–CX axis. (2) In addition to this form (TG), three other forms (GG, TT, and GT) exist in the gaseous, liquid, and glassy states. (3) In the liquid state, the TG form is the most stable and the GT form is the least stable. (4) The less polar TT and GT forms are more favored and the more polar TG and GG forms are less favored in the gaseous state than in the liquid state.