Microwave spectrum of dichloroacetaldehyde oxime

The microwave spectra of dichloroacetaldehyde oxime ((Cl2CHCH)-Cl-35=NOH) a nd its two isotopic species ((ClClCHCH)-Cl-37-Cl-35=NOH and (Cl2CHCH)-Cl-35 =NOD) were observed in the frequency range from 26 500 to 40 000 MHz. Their rotational constants and centrifugal distortion constants were determined: for the normal species in the ground vibrational state, A = 3149.619(242) MHz, B = 1368.304(13) MHz, C = 996.960(5) MHz, and Delta(JK) = 3.479(89) kH z. By referring to the values of the rotational constants and the planar mo ments (P-bb) and the r(s) coordinates of the chlorine and hydroxyl hydrogen atoms, we deduced the conformation of the molecule to be (E)-isomer with t he ac C-s symmetry plane. The bond length C-Cl, bond angle CICC, and dihedr al angle ClCCN, were determined to be 1.763(19) Angstrom, 110.4(17)degrees and 117.9(26)degrees, respectively. These values were in good agreement wit h those calculated by the ab initio MO calculations (MP2/6-31G** level). Th e C-C torsional frequency of (E)-dichloroacetaldehyde oxime was estimated t o be 77(35) cm(-1) from the relative intensity measurements. (C) 1999 Elsev ier Science B.V. All rights reserved.