Electron diffraction investigation of the molecular structures of isopropyl isocyanate and isopropyl isothiocyanate

The molecular structures of isopropyl isocyanate and isopropyl isothiocyanate have been determined by electron diffraction in the gas phase. For both molecules the data are consistent with the presence of a single conformer at room temperature, with the NCX group eclipsing one of the C---C bonds of the isopropyl group (a skew conformation). The structures found are consistent with the limited information available from microwave studies. The skeletal parameters found are (NCO, NCS; distances in pm, angles in degrees): r(C---N) 146.0(8), 145.9(13); r(C---C) 153.4(5), 15.8(7); r(N=C) 121.4(6), 120.1(6); r(C=O) 118.4(4); r(C=S) 159.8(5); NCC 110.0(5), 110.4(10); CCC 114.7(9), 115.7(13); C---N=C 132.6(10), 135.9(17); NCX 159(3), 166(3); C---N torsion 125(3), 115(6) (where a torsion angle of 120° corresponds to the skew form). The results are compared with those for some related molecules.