Reinvestigation of microwave spectrum, molecular structure, dipole moment, and theoretical calculation of s- trans ( E)- and s- trans ( Z)-acrylaldehyde oxime

Abstract

The spectroscopic constants of s- trans ( E)-acrylaldehyde oxime of normal, CH 2CHCHNOH, and deuterated, CH 2CHCHNOD, species were refined by adding a-type R-branch transitions observed in the frequency range of 34–40 GHz in the ground vibrational state. For s- trans ( Z) form, the spectroscopic constants of normal species were refined by refitting the reported frequencies with four b-type Q-branch transitions and those of deuterated species were determined by the least-squares fitting of the observed a-type R-branch transitions in the ground vibrational state. The spectroscopic constants of two isomers of normal species were also determined in the vibrationally excited states. The inertial defects (Δ I= I c − I a − I b ) of normal and deuterated species were determined to be −0.042(24) and −0.064(17) u Å 2 for s- trans ( E)-1 form, and −0.0536(8) and −0.063(11) u Å 2 for s- trans ( Z)-1 form, respectively. From the r s coordinates of the hydroxyl hydrogen atom determined for s- trans ( Z)-1 form, its OH bond was concluded to be at the trans position with respect to the CN double bond. The dipole moments of deuterated species of s- trans ( E)-1 form and those of normal and deuterated species of s- trans ( Z)-1 form were determined. The structural parameters of r(C 2C 3), ∠C 1C 2C 3, ∠C 2C 3N, and ∠C 3NO for s- trans ( E)-1 and s- trans ( Z)-1 forms were adjusted separately using to their rotational constants observed. It was found that the bond angle of ∠C 2C 3N in s- trans ( Z)-1 form are much wider than that in s- trans ( E)-1 form by about 10°. The difference between the observed and calculated (using MP2/6-311++G (d,p) level) rotational constants of s- trans ( Z)-1 form was larger than that of s- trans ( E)-1 form.