Microwave spectra, molecular structures, and theoretical calculations of s-trans-(E)- and s-trans-(Z)-crotonaldehyde oximes

摘要

The spectroscopic constants of s-trans-(E)- and s-trans-(Z)-crotonaldehyde oxime (Fig. 1) of normal, CH3CH=CH-CH=NOH, and deuterated, CH,CH=CH-CH=NOD, species were observed in the frequency range of 8-40 GHz in the ground vibrational state. The rotational constants of two isomers of normal species were determined to be A = 27,093(15 1), B = 1270.656(8), and C = 1223.288(8) MHz for s-trans-(E) form and A = 12,239(19), B = 1587.49(2), and C= 1417.80(2) MHz for s-trans-(Z) form. The inertial defects (Delta I= I-c-I-a-I-b) of normal and deuterated species were determined to be - 3.25(11) and - 3.24(20) u angstrom(2) for s-trans-(E) form, and - 3.191(73) and - 3.180(36) u angstrom(2) for s-trans-(Z) form, respectively. From the r(s) coordinates of the hydroxyl hydrogen atom determined for s-trans-(E) and s-trans-(Z) forms, their OH bonds were concluded to be at the trans position with respect to the C=N double bond. For s-trans-(E) form, the C-3-C-4 torsional excited vibrational states were observed up to v = 3. The vibrational frequency was found to be 90(40) cm - 1 from the relative intensity measurement. The vibrational mode was nearly harmonic. The structural parameters of r(C-4=N), r(C-3-C-4), angle C3C4N and angle-C4NO for s-trans-(E) and s-trans-(Z) forms were adjusted separately to their rotational constants observed. It was found that the bond angle of angle C3C4N in s-trans-(Z) form are much wider than that in s-trans-(E) form by about 10 degrees. The rotational constants observed for s-trans-(E) and s-trans-(Z) forms were consistent with those calculated using MP2/6-31G(d,p) rather than 6-311 + +G(d,p) basis sets, and those (B and C) calculated for s-trans-(E) using MP2/6-31G(d,p) were in excellent agreement with those observed. (c) 2005 Elsevier B.V. All rights reserved.