GENERATION AND MICROWAVE-SPECTRUM OF TRANS-1-CHLORO-2-NITROSOETHENE, CLCH=CH-N=O

trans-1-Chloro-2-nitrosoethene, ClCH=CH-NO (syn form: 8 in Fig. 1), ha s been generated in the gas phase from 1,1-dichloro-2-(hydroxyimino) e thane by pyrolysis or by chemical reaction of the precursor with NaHCO 3 and identified by microwave spectroscopy. The microwave spectrum has been observed in the frequency range from 8.0 to 40.0 GHz. The rotati onal constants (MHz) have been determined as A = 38 935 (147), B = 151 9.056 (6), and C = 1461.595 (6) for trans-(ClCH)-Cl-35=CHNO (Cl-35 spe cies) and A = 38 546 (81), B = 1481.667 (3), and C = 1426.835 (3) for trans-(ClCH)-Cl-37=CHNO (Cl-37 species). The observed inertial defects of the Cl-35 and Cl-37 species were found to be -0.099 (51) and -0.00 3 (30) u Angstrom(2), respectively. The nuclear quadrupole coupling co nstants (MHz) were determined to be chi(aa) = -50.4 (21) and chi(bb) = 31.1 (63) MHz for the Cl-35 species, and chi(aa) = -40.9 (10) and chi (bb) = 27.7 (22) MHz for the Cl-37 species. One vibrationally excited state was observed and assigned to the C-N torsional mode [120 (30) cm (-1)] that was almost harmonic. The observed pyrolysate was determined to be trans-1-chloro-2-nitrosoethene by comparing the observed and ca lculated rotational constants and coordinates of the chlorine atom. Th e ro structural parameters of r(C-Cl) and r(C=C) and bond angle of Cl- C-C were determined by fitting them to the observed rotational constan ts. Interesting reaction products, such as formyl chloride and hydroge n cyanide, were also detected during the pyrolysis of the precursor. T he lifetime of trans-1-chloro-2-nitrosoethene is ca. 1 min in the wave guide cell. (C) 1996 Academic Press, Inc.