Microwave Spectrum and Internal Rotation of Methylthiocyanate

Abstract

The microwave spectrum of methylthiocyanate has been investigated in the frequency range of 8–34 kMc/sec. The rotational constants determined from the spectrum are A=15 796.2, B=4155.4, and C=3354.2 Mc/sec. From the Stark effect of the low‐J lines, the dipole moment is found to be very nearly parallel to the principal a axis with a magnitude of 4.03 D. Splittings due to internal rotation (A—E splittings) are observed for rotational transitions in the ground and in the first excited torsional states. Analysis of these splittings gives an internal barrier of 556 cm⁻¹. Two sets of vibrational satellite lines are found for all the low‐J transitions. They are believed to be associated with the first two excited states of a bending vibrational mode of frequency about 160 cm⁻¹. A structure of the molecule which is consistent with the rotational constants is C–H=1.093 Å, ∠HCH=109°28′, C–S (CH₃–S)=1.820 Å, C–N=1.156 Å, S–C=1.684 Å, and ∠CSC=99°52′.