Hydrogen bond CH…O in liquid methanol

Using the C–O stretch to unravel the nature of hydrogen bonding in low-temperature solid methanol–water condensates

“…Therefore, not unlike the liquid phase, in the bulk amorphous solid it is highly likely that the methyl group does indeed participate in hydrogen bonding. Thus the increasing blue-shift in the C-H bands below R=0.6 − 0.7 that we see in Figures 5 and 6 strongly suggest that the methyl group begins to form hydrogen bonds, most likely with H 2 O molecules due to higher H 2 O concentrations at low R. Interestingly this is also around the mixing ratio where we hypothesise the change in the bonding environment observed in Figure 4 showing the variation in the O-H stretch position as a function of R. The splitting of the C-H stretch region in the mixed samples into four distinct bands compared to that of the less defined region in pure CH 3 OH in fact suggests that only one CH 3 hydrogen participates in a hydrogen bond 37 . This may also explain the comparatively smaller blue-shift of the symmetric stretch band (ν s ) compared to the asymmetric bands(ν a ).…”

“…In CH 3 OH the vibrational spectra of the O-H, C-H and the C-O stretch are sensitive to the interaction between nearest neighbours. The interactions between CH 3 OH and H 2 O have been studied in mixed CH 3 OH/H 2 O liquids [29][30][31][32] , heterodimers [33][34][35] and small clusters both in the gas phase and in matrix isolation studies 33,34 , supported with extensive computational studies [36][37][38][39][40][41][42][43][44] . The O-H stretch has been used extensively to study hydrogen bonding between H 2 O and CH 3 OH in dimers, matrix isolation and in clusters, however, in the bulk condensed and liquid phases this poses a problem as the broad absorption bands due to the O-H stretching frequencies of both CH 3 OH and H 2 O overlap.…”

Polarized Infrared Spectra of the H(D) Bond in 2‐Thiophenic Acid Crystals: A Spectroscopic and Computational Study

“…The third approximation neglects the electrical anharmonicity, which is quite a strong effect that cannot be discarded in the treatment of the IR line shape of the stretching mode ν S (XH⋅⋅⋅Y) of H‐bonded species, especially for strongly H‐bonded systems in polar solvents 67. The removal of this approximation in the present approach may be justified by the fact that the spectra have been measured using an inert solvent (CCl 4 ), and therefore the mutual interactions of 2TPA dimers with the solvent will not affect the IR line‐shape transitions.…”

BCL3 gene role in facial morphology

“…This inability to reproduce some details of the fine structure was yet met for precedent works using the same model and dealing with other more complex molecules. It may be explained by the fact that the model used ignored Fermi resonance [13, 25, 26], anharmonicity of the fast modes19, and the electrical anharmonicity, which is a quite strong effect that cannot be discarded in the in the area of the IR line shape of stretching mode υ XH of H‐bonded species, especially for H‐bonded system in polar solvents27.…”