THE MICROWAVE-SPECTRUM AND POTENTIAL FUNCTION OF NITROSOETHANE, CH3CH2NO

The potential function for internal rotation of the nitroso group in n itrosoethane, CH3CH2NO, has been determined. All available microwave d ata are fitted to the potential, [GRAPHICS] where V-1 = (-15), V-2 = 6 3(2), V-3 = 389(1), V-4 = 135(1) and V-5 = 166(2) cm(-1). Torsional fu ndamentals for the nitroso group (C-N) have been measured by microwave relative intensity measurements for both rotamers: nu(t)(cis) = 182(1 7) cm(-1) and nu(t)(gauche) = 61(19) cm(-1). The energy difference bet ween the two stable conformers has been determined to be Delta W(gauch e - cis) = 2.1(4) kJ mol(-1). The ground state torsional splitting for gauche CH3CH2NO has been re-evaluated as Delta E(+/-) = 153.5(4) MHz corresponding to a calculated value of the coupling constant T-be = 34 .7 MHz. Accurate structural data have been used in the potential funct ion calculations. The resulting potential is compared with those of so me isoelectronic molecules.