Microwave spectrum, conformer, and ab initio MO calculation of (E)-chloropropanone oxime

The microwave spectrum of chloropropanone oxime was observed in the frequen cy range from 26.5 to 40.0 GHz. The rotational constants (A-level) (MHz) we re determined as A = 6501.04(15), B = 1464.98(1), and C = 1326.80(1) for (C lCH2C)-Cl-35(CH3)=NOH(Cl-35 species) and A = 6519.5(15), B = 1428.07(1), an d C = 1298.00(1) for (ClCH2C)-Cl-37(CH3) = NOH(Cl-37 species) in the ground Vibrational state. The values of Delta I(= I-c-I-b-I-a) obtained for the C l-35 and Cl-37 species were found to be -41.811(7) and -42.06(2) u Angstrom (2), respectively. The observed rotational constants, Delta I, and r(s)-coo rdinates of the chlorine atom were in good agreement with those of anticlin al form in E-isomer (E-ac), having the dihedral angle (phi) of ClC1C2N = 11 6.8 degrees, as shown in Fig. 2. One vibrationally excited state was observ ed and assigned to the C-1-C-2 torsional mode (80(20) cm(-1)). (C) 2000 Els evier Science B.V. All rights reserved.