High Overtones of the C−H Stretching Vibrations in Anisole and Thioanisole

Abstract

The high overtone C−H stretching vibrations of anisole and thioanisole have been measured in liquid phases by using optical absorption and optoacoustic spectroscopy. The local mode model satisfactorily describes the experimental data and provides anharmonicities and force constants. The data obtained by the DFT calculations allow a complete assignment of all the observed bands in the vibrational spectra of the two molecules. The comparative analysis of the overtone spectra and of the DFT results confirms the occurrence of the methyl C−H symmetric stretching at low wavenumber (∼2836 cm-1) in anisole as due to a strong anharmonic coupling, deriving from a Fermi resonance with the first overtone of the methyl symmetric deformation mode. This effect is typical of the methoxy group, because it does not occur in thioanisole as well as in toluene. The present investigation demonstrates the existence of a strong effect of electron conjugation of OCH3 toward the aromatic system, in comparison with the SCH3 group, as evidenced also by the study of the rotational barriers and the proton magnetic resonance data.

Eco-Friendly Strategy to Improve the Processiblity and Properties of Poly(vinyl alcohol) Foams Based on a 3D Hydrogen-Bond Network

“…FTIR spectroscopy spectra also provided powerful and direct evidence to demonstrate the variations of functional groups after the purification of LS. The band at 1041 cm –1 was assigned to the SO stretching vibration, which was more obvious in LA than LS. , The stretching of asymmetric and symmetric C–H of methoxy groups on the aromatic ring skeleton at 2929 and 2836 cm –1 intensified is considered to depend on the reduction of reducing sugars . Furthermore, the peak of CO shifted from 1602 to 1616 cm –1 , which is considered as the conversion of carboxylate into carboxylic acid, forming strong intramolecular and intermolecular H-bond interactions with PVA .…”

“…43,44 The stretching of asymmetric and symmetric C−H of methoxy groups on the aromatic ring skeleton at 2929 and 2836 cm −1 intensified is considered to depend on the reduction of reducing sugars. 45 Furthermore, the peak of CO shifted from 1602 to 1616 cm −1 , which is considered as the conversion of carboxylate into carboxylic acid, forming strong intra- molecular and intermolecular H-bond interactions with PVA. 46 Moreover, based on the SEM images in Figures S1 and 2c, the LS with impurities presented a snowflake morphology, and the purified LA from LS had an average diameter of around 130 nm, attributed to the hydrophilic sulfonic acid and hydroxyl groups, hydrophobic phenylpropane, and aromatic rings structures.…”

Excited state deactivation pathways of neutral/protonated anisole and p-fluoroanisole: a theoretical study

“…In the present study, protonation effects on the electronic transition energies and photophysical behavior of anisole and p-fluoroanisole will be addressed based on the CC2/MP2 methods. Anisole has been the subject of many experimental [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] and theoretical [61][62][63] studies. The high resolution S 1 -S 0 electronic excitation spectrum of anisole has been recorded in a molecular beam experiment by F. Lahmani et al 64 and later by C. G. Eisenhardt et al 48 It has been shown that the band origin of the S 1 -S 0 electronic transition of anisole lies at 36 386 cm À1 (4.512 eV).…”

Infrared Spectra of Dimethylphenanthrenes in the Gas phase

“…They are aromatic C–H and methyl C–H stretching vibrations. The assignment of the observed bands in this region is always difficult because of the presence of Fermi resonances . In the aromatic C–H stretching region, Fermi resonances occur due to the interaction of a fundamental mode with a lower frequency overtone or combination mode, whereas, in the methyl C–H stretching region, they generally occur due to the interaction between the methyl C–H symmetric stretch and an overtone involving two quanta of a methyl deformation mode.…”