Robert P. Lattimer

Microwave Spectrum of Methylhydrazine; Rotational Isomerism, Internal Motions, Dipole Moments, and Quadrupole Coupling Constants

The microwave spectrum of methylhydrazine has been investigated. Two rotamers have been observed, and their spectra have been assigned and analyzed. The ground‐state rotational constants of the inner skew rotamer are A = 36 704.37 MHz, B = 9689.70 MHz, and C = 8531.95 MHz, while the values obtained for the outer skew rotamer are A − C = 29 597.20 MHz and κ = − 0.925849. Strong evidence for the conformational identifications was provided by the measured dipole moment components, which were μa = 1.04 D, μb = 1.21 D, μc = 0.46 D for the inner rotamer and μa = 0.26 D, μb = 0.60 D, and μc = 1.70 D for the outer rotamer. Relative intensity measurements indicate that the inner rotamer is more stable than the outer rotamer by 293 ± 23 cm−1. Spectral splittings produced by inversion and methyl tunneling have been observed. Analysis of the latter effect leads to a barrier of V3 = 1329 cm−1 for the inner rotamer. Hyperfine splittings of the inner rotamer spectrum were described by the single set of 14N quadrupole co...