Rotational spectra, electric dipole moment and methyl group internal rotation barrier of 1,1,1-trifluoropropane

Abstract

The microwave spectra of the main species of 1,1,1-trifluoropropane and the three singly substituted ¹³C isotopic species have been studied in the frequency region 6–40 GHz using Stark modulation and Fourier-transform microwave spectroscopy. Accurate rotational spectroscopic constants and quartic centrifugal distortion constants have been obtained for the ground vibrational state. A reasonable molecular structure has been derived from the rotational constants and planar moments of inertia. The barrier to internal rotation of the methyl top has been determined from the A–E splittings to be 2635(4) cal mol¹¹. The dipole moment components have been computed from Stark effect measurements to be µ_a = 2.172(4) D and µ_b = 1.140(9) D with a total dipole moment of µ = 2.453(8) D.