Microwave Spectrum, Structure, and Dipole Moment of s-trans Acrolein

Abstract

The microwave spectrum of acrolein has been studied in the 19–37 kmc region. A series of R-type transitions was identified for the ground and three excited torsional states of the s-trans isomer and these spectra were successfully fitted in the rigid rotor approximation. Using the ground state moments and additional electron diffraction data a reasonable though not unique structure has been obtained. The torsional frequency was found to be 200±50 cm—1 from relative intensity measurements, and a lower limit of about 2300 cal was estimated for the barrier hindering trans-cis conversion. The dipole moment for the ground state was found to be 3.11±0.04 d, oriented about 14° from the carbonyl group. The results obtained and the absence of a strong s-cis spectrum establish the s-trans isomer as the predominant form.

Generation, Microwave Spectrum, Barrier to Internal Rotation of Methyl Group, and ab Initio MO Calculation of syn-2-Nitrosopropene, syn-CH2C(CH3)NO

“…Table 13 shows the comparison of the dipole moments of syn-CH 2 ACHOY and syn-CH 2 AC(CH 3 )OY (Y ϭ NO and CHO). The total observed for syn-2-nitrosopropene was almost the same as that of syn-nitrosoethene (2), within the limits of error, while the total of syn-methacrolein (13) was smaller than that of syn-acrolein (10). It was found that the trend of the total dipole moment of syn-nitrosoethene and syn-acrolein decreases with the methyl effect.…”

“…The two rotational isomers of CH 3 CH 2 -Y (Y ϭ NO (8) and CHO (9)) were determined by microwave spectroscopy to be cis ( ϭ 0°) and skew ( ϭ 120°, : dihedral angle of C-C-N-O in CH 3 CH 2 -NO and C-C-C-O in CH 3 CH 2 -CHO) forms. The values of V 3 in cis and skew forms of CH 3 CH 2 -NO (8) were found to be 2578(40) and 2586 (10) cal/mol, while those in cis and skew forms of CH 3 CH 2 -CHO (9) were found to be 2195 (23) and 2532 (29) cal/mol, respectively. The value of V 3 of cis-CH 3 CH 2 -NO was higher than that of cis-CH 3 CH 2 -CHO by ca.…”

“…In the case of molecules with an alkene group, two molecular configurations of CH 2 ACHOCHO were determined by microwave spectroscopy to be syn (10) and anti forms (11), while gas-phase Raman spectroscopy revealed that the syn form was more stable than the anti form by 594 (14) cm Ϫ1 (12). On the other hand, the molecular conformation of CH 2 ACHONO (2) was determined by microwave spectroscopy to be only the syn form, which was consistent with the ab initio MO calculation (MP2/6-31G**) showing that the anti form was considerably less stable than the syn form with energy greater by 1394 cm Ϫ1 (2).…”

Structure and conformation of nitroxyl spin-label compounds in frozen solutions by electron nuclear double resonance spectroscopy

“…The ENDOR determined structure of Iis identical to the corresponding structure defived ffom X-ray diffraction studies [17]. Wagner and coworkers have estimated that the potential energy of s-trans acrolein is about 2.5 kcal/mol lower than the s-cis conformer, and only about 2 % of the molecules in solution at room temperature are in the s-cis conformation [29]. On this basis we anticipate that the s-trans conformation of II found in this study is similarly energetically favored over the s-cis conformation.…”

A Search for Interstellar Molecular Lines in the Frequency Range 8·6 to 9·2 GHz

“…§ Peak-to-peak, channel-to-channel. II References to transition frequencies: 1, Bowater et al (1971); 2, Sorensen (1967); 3, Kirchhoff et al (1971); 4, Wagner et al (1957); 5, Johnson et al (1971).…”