Generation and Microwave Spectrum of trans-Nitrosoethylene, CH 2CH-NO

Abstract

The microwave spectrum of trans-nitrosoethylene (nitrosoethene) generated by pyrolysis of chloroacetaldehyde oxime has been observed in the frequency range from 8.0 to 50.0 GHz. The rotational constants (MHz) have been determined as A = 52 635(172), B = 5071.56(3), and C = 4625.91(3)in the ground vibrational state. The inertial defect is found to be −0.002(33)u Å 2. The nuclear quadrupole coupling constants (MHz) due to each nitrogen atom are determined to be χ aa = 0.34(43), χ bb = −6.28(33), and χ cc = 5.94(76). The dipole moments (Debye) obtained are μ a = 2.67(3), μ b = 0.748(7), and μ total = 2.77(3). Two excited vibrational states are assigned: the C-N torsional mode [150(20)cm −1] and the in-plane mode [490(50) cm −1]. The C-N torsional vibration was almost harmonic. This fact and the obtained inertial defect suggest that trans-nitrosoethylene has a planar structure. The lifetime of trans-nitrosoethylene is ca. 30 sec in the waveguide cell. We detected trans-nitrosoethylene in the gas phase, which has not been reported before.