The microwave spectrum and potential function of nitrosoethane, CH 3CH 2NO

Abstract

The potential function for internal rotation of the nitroso group in nitrosoethane, CH 3CH 2NO, has been determined. All available microwave data are fitted to the potential, V(α) = 1 2 ∑ n V n[1 − cos(nα)] where V 1 = (−15), V 2 = 63(2), V 3 = 389(1), V 4 = 135(1) and V 5 = 166(2) cm −1. Torsional fundamentals for the nitroso group (CN) have been measured by microwave relative intensity measurements for both rotamers: v t (cis) = 182(17) cm −1 and v t (gauche) = 61(19) cm −1. The energy difference between the two stable conformers has been determined to be ΔW(gauche - cis) = 2.1(4) kJ mol −1. The ground state torsional splitting for gauche-CH 3CH 2NO has been re-evaluated as ΔE ± = 153.5(4) MHz corresponding to a calculated value of the coupling constant T bc = 34.7 MHz. Accurate structural data have been used in the potential function calculations. The resulting potential is compared with those of some isoelectronic molecules.