Barrier Studies in the Halopropenes. I. The Microwave Spectrum, Barrier to Internal Rotation, Quadrupole Coupling Constants, and Microwave Double-Resonance Spectra of 2-Chloropropene

Abstract

The microwave spectra of CH3C35Cl:CH2 and CH3C37Cl:CH2 have been observed in the ground and first excited torsional states. The ground-state rotational constants of CH3C35Cl:CH2 are A=9272.79±0.10 Mc/sec, B=4983.84±0.10 Mc/sec, and C=3304.39±0.10 Mc/sec. The ground-state rotational constants for CH3C37Cl:CH2 are A=9272.31±0.10 Mc/sec, B=4850.48±0.10 Mc/sec, and C=3245.11±0.10 Mc/sec. The quadrupole coupling constants along the appropriate principal inertial axes in the ground torsional state of CH3C35Cl:CH2 are χaa=−68.15±0.10 Mc/sec, χbb=37.11±0.10 Mc/sec, and χcc=31.04±0.10 Mc/sec. The quadrupole coupling constants for CH3C35Cl:CH2 in the excited torsional state were within the experimental error of the corresponding ground-state values. The quadrupole coupling constants in CH3C37Cl:CH2 are χaa=−53.80±0.10 Mc/sec, χbb=29.30±0.10 Mc/sec, and χcc=24.50±0.10 Mc/sec. Analysis of the first excited-torsional-state rotational spectrum yielded a barrier to the internal rotation of the methyl group of 2671±20 cal/mole. Microwave double-resonance experiments were used to provide a positive confirmation for the assignments of the 000→101 and 101→202 transitions in CH3C35Cl:CH2 as well as exhibiting some interesting features in the energy levels involved in the transitions. Two types of experiments were performed. The first experiments involved irradiating the quadrupole components in the 000→101 transition while observing the 101→202 transition. The second set of experiments involved irradiating one of the quadrupole components in the 000→101 transition and using a second klystron to observe the entire 000→101 triplet.