Normal coordinate analyses of three isomeric acetylpyridines and acetophenone

Abstract

Normal coordinate analyses for 2-, 3-and 4-acetylpyridine and acetophenone were carried out employing a systematic procedure based on a modified valence force field that is comparable to those used previously for different aromatic molecules. The general valence force fields (GVFF) were determined using a set of 41 parameters (25 planar and 16 non-planar) for the above compounds to compare the observed wavenumbers with the calculated values satisfactorily with an average error of 7.0 cm −1 (0.82%) for in-plane and 9.2 cm −1 (1.60%) for out-of-plane modes. On the basis of the calculated potential energy distribution, certain revisions of the previous assignments were made. The decomposition of the normal mode wavenumbers into those related to different internal coordinates is discussed. EXPERIMENTALThe three isomeric acetylpyridines and acetophenone were supplied by Fluka, Ega-Chemie, Sigma and SRL (India) in 98%, 99%, 97% and 99% purity, respectively and they were further purified by vacuum distillation. IR spectra were measured on thin films on a previously calibrated Perkin-Elmer Model 783 IR spectrophotometer. The resolution of the IR band is about 2 cm 1 for sharp bands and slightly less for the broader bands.Raman spectra of pure samples were recorded with a Spex Raman spectrometer (Ramalog) system, fitted with an argon ion laser using 488 nm as the excitation wavelength, interfaced with a computer in the photon counting mode. The slit widths of the monochromators were adjusted to obtain reasonably good Raman spectra. The detection system used is was a R928-7 PMT from Hamamatsu Photonics, attached to the spectrometer and held in a cryostat (Spex model 1730) having a suitable resistor network. The laser power was kept at 200 mW. Polarized Raman spectra were recorded with an arrangement

Vibrational spectra and computational study of 3-amino-2-phenyl quinazolin-4(3H)-one

“…For some modes, this splitting is so small that they may be considered as quasi-degenerate and for the other modes a significant amount of splitting is observed. Such observations have already been reported [74][75][76][77].…”

Concentration-dependent surface-enhanced Raman scattering of 2-benzoylpyridine adsorbed on colloidal silver particles

“…1 shows the molecular structure of 2-BP. Vibrational assignment of these [17] and of similar molecules [18][19][20][21][22][23] with monosubstituted benzenes and pyridines and molecules containing two or more aromatic rings (homo-and hetero-) is reported in the literature. The SER spectra of such molecules are found to be very sensitive to the small change of their concentration in silver colloidal solution.…”

FT‐IR, FT‐Raman and DFT calculations of the salicylanilide derivate 4‐chloro‐2‐(4‐bromophenylcarbamoyl)phenyl acetate

“…For some modes, this splitting is so small that they may be considered as quasi-degenerate and for other modes a significant amount of splitting is observed. [47,49] The existence of one or more aromatic rings in the structure is normally determined from the C-H and C C-C ring related vibrations. The C-H stretching occurs above 3000 cm −1 and is typically exhibited as multiplicity of weak to moderate bands, compared with the aliphatic C-H stretching.…”