Vibration Spectra and Rotational Isomerism of Chain Molecules. I. Methyl Propyl Ether, Ethyl Propyl Ether, and Butyl Methyl Ether

Abstract

The Raman and infrared spectra of methyl propyl ether, ethyl propyl ether, and butyl methyl ether were measured for the gaseous, liquid, glassy and crystalline states. The normal vibration frequencies were calculated, a consistent set of force constants explaining the frequencies of basic aliphatic ethers being assumed. The rotational isomerism was studied and the following conclusions were obtained. (1) Only the all-trans form exists in the crystalline state. (2) Another form which takes the gauche conformation about the OC–CC axis and the trans conformation about the CC–CC and CO–CC axes exists in the glassy state. (3) Other forms also exist in the liquid state. These results confirmed that the repulsive force between nonbonded hydrogen atoms was one of the important factors influencing the stability of molecular conformations. The stable conformations of the ether molecules were correlated with those of polyether chains.