SPECTRA AND STRUCTURE OF SMALL RING COMPOUNDS .58. STRUCTURAL PARAMETERS FOR CHLOROCYCLOBUTANE FROM COMBINED MICROWAVE DATA AND ABINITIO CALCULATIONS

The structural parameters of chlorocyclobutane, c-C4H7Cl, have been obtained from ab initio Hartree-Fock calculations employing the 6-31G* basis set for both the more stable equatorial and the high energy axial conformers. The determined carbon-hydrogen distances were adjusted by 0.010 angstrom and held fixed while a weighted least-squares adjust was used to obtain all of the heavy atom parameters for the equatorial conformer by fitting the rotational constants of nine isotopic species. The determined r(O) parameters are: r(C-alpha - C-beta) = 1.535(8) angstrom; r(C-beta - C-gamma) = 1.548(3) angstrom; r(C-alpha - Cl) = 1.788(9) angstrom; negative of < C-beta-C-alpha-C-beta' - Cl = 132.0(2)degrees, negative of < C-beta-C-alpha-C-beta' = 89.7(6)degrees, negative of < C-alpha-C-beta-C-gamma; = 87.1(2)degrees, and negative of < C-beta-C-gamma-C-beta' = 88.7(2)degrees. These results are compared to the calculated values as well as those obtained earlier from electron diffraction and microwave studies.