Microwave Spectrum of Normal Propyl Chloride

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Abstract
The microwave spectrum of gaseous normal propyl chloride reveals the presence of two rotational isomers, the trans and gauche conformations. The ground vibrational state rotational constants found for the more abundant Cl35 species are, for the gauche form, A = 11829.22, B = 3322.58, C = 2853.06 Mc/sec; for the trans form, B = 2379.7, C = 2271.7 Mc/sec. Analysis of quadrupole hyperfine splittings in the spectrum of the gauche form gives the quadrupole coupling constants χaa = —19.41 Mc/sec, η = 2.105, in the principal axis system of the Cl35 species. Satellite spectra rising from excited vibrational states were also observed: in the gauche form, the first and second excited states of the skeletal torsion were assigned, and another satellite is believed to be from the excited methyl torsion; in the trans form, only the first excited state of the skeletal torsion was assigned. From relative intensity measurements, it is concluded that the energy difference between the trans and gauche isomers is 0±0.5 kcal/mole.