The molecular structure of the anti conformation of vinylcyclopropane as determined by combined electron diffraction and microwave analysis

The electron diffraction data for vinylcyclopropane collected at 273 K and the rotational constants for the parent and four C-13 isotopic species of the anti form were analyzed. A mixture of anti (76(10)%) and gauche forms was observed in the vapor phase. The geometrical parameters (r(g)/angle(alpha) obtained from least squares analysis are as follows: r(C-H)(av) = 1.098(3) Angstrom, r(C-1-C-2) = 1.521(4) Angstrom, r(C-1 -C-2) - r(C-2-C-3) = 0.011(6) Angstrom, r(C-1-C-4) = 1.481(7) Angstrom, r(C-4 = C-5) = 1.340(2) Angstrom, angleC(3)C(1)C(4) = 118.2degrees (5), angleC(1)C(4) = C-5 = 125.8degrees (6), angleHC = C-4(5) = 116.8degrees (25), angle(HCC)(C3) = 118.0degrees (6), tauH(6)C(1)C = C-4(5) = 0.0degrees (anti); 124degrees (18) (gauche) and %anti = 76(10). (C) 2003 Elsevier Science B.V. All rights reserved.