The Infra-Red Absorption Spectrum of Methylamine Vapor

Abstract

The infra-red absorption of methylamine vapor has been measured from 2 to 18μ with a cell of 18 cm length using pressures from 2 to 55 cm. A total of nineteen bands has been observed, nine of which are assigned to fundamental vibrations. The bending vibrations of the two groups give rise to several bands in the region from 6 to 8μ. This causes considerable overlapping which makes it difficult to locate band centers and to determine band types in this region. Three bands which originate from the C – H vibrations occur at wave-lengths between 3.0 and 3.6μ. A band due to the N – H parallel valence vibration has been found at 2.98μ. The most intense band in the spectrum occurs at 12.9μ, and arises from a bending vibration of the hydrogen atoms in the amino group. The parallel vibration between the methyl and amino groups gives rise to an intense band at 9.56μ. This is a parallel band having a sharp and intense zero branch. A band also due to a bending vibration in the amino group was observed at 16μ, and from the experimental curve it can not be said whether it is parallel or perpendicular; hence definite assignment is not made. The other bands which have been observed have been assigned to overtones and combinations.