MICROWAVE-SPECTRUM, MOLECULAR-STRUCTURE, AND AB-INITIO CALCULATION OF(E)-CHLOROACETALDEHYDE OXIME

The microwave spectra of (E)-(ClCH2CH)-Cl-35=NOH, (E)-(ClCH2CH)-Cl-37= NOH, (E)-(ClCH2CH)-Cl-35=NOD, and (E)-(ClCH2CH)-Cl-37=NOD have been ob served in the frequency range from 26.4 to 40.5 GHz. The rotational an d centrifugal distortion constants of the four isotopic species in the ground and excited vibrational states were determined, The values of the Delta I(=I-f -I-a -I-b) obtained for the normal (Cl-35 and Cl-17) and deuterated (Cl-35 and Cl-37) species in the ground vibrational sta te were found to be -16.350(4), -16.36(4), -17.06(4), and -17.07(6) u Angstrom(2), respectively. The molecular structure of this molecule wa s determined to be the anticlinal form (phi(1):angle ClCCN = 121.4 deg rees, phi(2):angle CNOH = 180.0 degrees), as shown in Fig. l(a). It wa s found that ab initio calculation of MP2/6-31G* level can be used to predict the most stable rotational conformer of (E)-ClCH2CH=NOH, The seven structural parameters of the heavy atom skeleton of this molecul e were fitted to the eight rotational constants (B and C) of the four isotopic species. The obtained structural parameters (r(0)) are almost the same as those (r(alpha)) Obtained previously by a gas-phase elect ron diffraction study (K. Iijima, T. Miwa, T. Sakaizumi, O. Ohashi, J, Mol. Struct. 352/353 (1995) 161), within the errors. The r(C=N) and a ngle CCN obtained for (E)-ClCH2CH=NOH are slightly shorter and drastic ally narrower than those of (Z)-ClCH2CH=NOH. The trend is consistent w ith those of CH3CH=NOH and CH3CH2CH=NOH. (C) 1997 Elsevier Science B.V .