MICROWAVE-SPECTRUM AND MOLECULAR-STRUCTURE OF (Z)-CHLOROACETALDEHYDE OXIME

The microwave spectra of (Z)-(ClCH2CH)-Cl-35=NOH, (Z)-(ClCH2CH)-Cl-37= NOH, (Z)-(ClCH2CH)-Cl-35=NOD, and (Z)(ClCH2CH)-Cl-37=NOD have been obs erved in the frequency range from 16.5 to 40.0 GHz. The rotational and centrifugal distortion constants of four isotopic species and the nuc lear quadrupole coupling constants of the Cl-35 species were determine d. The values of planar moment (P-alpha = (I-a + I-b - I-c)/2) Obtaine d for four isotopic species were found to be 1.761(14), 1.800(18), 1.7 77(19), and 1.770(18) u Angstrom(2) in the ground vibrational state. T he unchanged values of P-cc shaw that the chlorine and hydroxyl hydrog en atoms lie in or are very close to the ab inertial plane of the mole cule. The conformation of the Z-ferm was determined to be Calcd I (phi (1) = 180 degrees, phi(2) = 180 degrees), as shown in Fig. 1, from the comparison of the observed and calculated rotational constants and co ordinates of the chlorine and hydroxyl hydrogen atoms. The determined conformation is consistent with that reported by an electron diffracti on study (K. Iijima, T. Hanamori, T. Sakaizumi, and O. Ohashi, J. Mol. Struct. 299, 149-153 (1993).). One excited vibrational state is assig ned to the C-C torsional mode, and it is anharmonic. This fact is also consistent with the result of a large amplitude motion about the C-C single bond reported by a gas-phase electron diffraction study. Assumi ng the skeleton of the heavy atoms is a planar molecule, the seven str uctural parameters of the Z-form (anti-form) were fitted to the eight rotational constants (B and C) of four isotopic species. The obtained structural parameters (r(0)) are almost the same as those obtained by electron diffraction study (r(alpha)) within the errors. (C) 1996 Acad emic Press, Inc.