Electron Diffraction Study on the Rotational Isomerism in n-Propyl Chloride

Abstract

The molecular structure and the rotational isomerism of n‐propyl chloride were investigated by means of the sector‐microphotometer method of electron diffraction. The following structural parameters were obtained: C–Cl=1.77₅±0.02 A, C–C=1.53₅±0.02 A, and ∠C–C–Cl=111°±2°. It was confirmed that there are two isomers in the vapor phase; one is the trans‐form, and the other is the gauche‐form. From the analysis of the scattering intensity of the small‐angle region (q=5∼15), the angle of ∠C–C–C, the azimuthal angle of the gauche‐form, and the fraction of the trans‐form were found to be 109.5°±2.5°, 59°±5°, and 19±5%, respectively. It was also found through the calculation of the partition functions that the gauche‐form is only a few hundred calories/mole more stable than the trans‐form, in fairly good agreement with the spectroscopic results. The procedure used in the analysis of the small‐angle region is described in detail.