Torsional frequency, barrier to internal rotation, and dipole moment of N-sulphinylaniline from microwave rotational spectra

Microwave spectra of the ground and first three excited torsional states of N-sulphinylaniline have been assigned. The variation of the inertial defect with torsional number shows the molecule to be planar. The torsional frequency has been determined as ν = 41.1 cm ^-1 and the barrier to internal rotation as V₂ = 2.3 kcal/mole. From the splittings of the Stark lobes of some lines the values μ_a = 2.20 ± 0.06, μ_b = 0.664 ± 0.005, and μ_tot = 2.30 ± 0.06 were obtained.