Spectra and structure of small ring compounds. XXXI Microwave, Raman and infrared spectra, conformation, dipole moment, and quadrupole coupling constants of 2-oxazoline

Abstract

The microwave spectrum of 2-oxazoline has been recorded from 12.4–40.0 GHz. Both Q-branch and R-branch assignments have been made for the ground and five vibrationally excited states of the ring puckering mode for both A - and B-type transitions. The components of the diple moment were determined by the Stark effect to be μa = 1.14±0.01, μb = 1.35±0.01, μc = 0.00±0.00, and μt = 1.77±0.01 D. The quadrupole coupling constants were found to have the following values: χa a = −3.54, χb b = 2.03, and χc c = 1.51 MHz. From the inertial defect Δc and the dipole moment, it is concluded that the heavy atom skeleton is planar. From the relative intensity measurements, the first excited state of the ring puckering vibration was found to have a frequency of 79±8 cm−1 and from a series of difference bands in the infrared spectrum, the ν = 0→1, 1→2, 2→3, 3→4, and 4→5 transitions were found to have the following frequencies: 74, 95, 103, 110, and 117 cm−1, respectively. The potential function governing the ring puckering motion was found to be of the form V = 22.2 (Z4+1.31Z2), where Z is the reduced ring puckering coordinate. The Raman spectra of gaseous, liquid, and solid 2-oxazoline was investigated from 0–3500 cm−1 and the infrared spectra of the gas and solid were recorded from 33–3500 cm−1. The vibrational assignment of the fundamentals is proposed which is consistent with the Cs conformation. The assignment is based on the gas-phase band contours, the depolarization values, and group frequency correlations. The number of lattice modes indicate that there are at least two molecules per primitive cell. The results are compared with those obtained for other similar five-membered rings.

Microwave Spectrum and Intramolecular Hydrogen Bonding of 2-Isocyanoethanol (HOCH2CH2N≡C)

“…This spectrum was soon identified to belong to 2-oxazoline by means of its reported MW spectrum. 56 2-Oxazoline is much more volatile than 2-isocyanoethanol, whereas the other impurity, unreacted HOCH 2 CH 2 NHCHO, has much lower volatility. It was therefore pumped several minutes on the sample at room temperature before filling the cell with fresh sample in order to get rid of as much 2-oxazoline as possible.…”

“…This compound was found to have a symmetry plane (C s symmetry) according to the CCSD(T) computations, in agreement with the spectroscopic study. 56 The CCSD(T) electronic energy of 2-oxazoline is lower than the electronic energy of conformer V by 73.67 kJ/mol, as can be calculated from the entries of Tables 10S and 11S of the Supporting Information.…”

Poly(oxazoline) for the design of amphiphilic silicone coatings

“…In the wavenumber range of 1200 2000 cm -1 , the Raman spectrum of PEG is characterized by well-resolved bands at 1482 cm -1 attributed to the deformation of CH2 scissoring vibration with a contribution of backbone (OCC--) deformation, and two bands located at 1279 and 1233 cm -1 assigned to the gauche mode vibration and the trans mode vibration of the CC-group, respectively [41,42]. The Raman spectrum of POx is characterized mainly by a broad band centred at 1635 cm -1 attributed to the CNstretching vibrations and broad bands in the 1400-1500 cm -1 range (with peaks located at 1483, 1467 and 1439 cm -1 assigned to the in plane bending of the CH2 groups [43].…”

Remoistenable temporary supports for facing of canvas paintings

“…Here, the peak at 1635 is supposed to correspond to v(C=O) modes (Sun, and Wu 2015). The region included between 1390 and 1530 cm −1 , with peaks at 1429, 1460 and 1482 cm −1 , corresponds to δ(CH2) modes (Durig, Riethmiller, and Li 1974).…”

“…It has been suggested that bands between 250 and 560 cm −1 could are due to vibration about the C-C-N bond (Socrates 2001), while the others included in the region 930-1300 cm −1 are overtones of different vibrational mode of CH2 bonds (Durig, Riethmiller, and Li 1974).…”