In addition, 1525 new transitions belonging to the Tetradecad-Pentad hot band system were assigned for the first time, up to J = 20. In particular, rotational assignments in the cold band and in the first related hot band (Octad-Dyad) were extended up to J = 30 and 27, respectively. Thanks to the high temperature, new assignments of vibration-rotation methane line positions have been achieved successfully in the Pentad system and some associated hot bands (Δn = Â☒) observed in the spectral region 2600-3300 cm-1. This work follows our recent global analysis of the Dyad system Δn = Â☑ (1000-1500 cm-1), with n being the polyad number. The ν3 C-H stretching region of methane was reinvestigated in this work using high temperature (620-1715 K) emission spectra recorded in Rennes at Doppler limited resolution. New investigation of the ν3 C-H stretching region of 12CH4 through the analysis of high temperature infrared emission spectraĪmyay, Badr Gardez, Aline Georges, Robert Biennier, Ludovic Vander Auwera, Jean Richard, Cyril Boudon, Vincent The resulting blue shift of this stretching frequency is substantial and amounts to almost 35 and 170 cm(-1), respectively. These changes are largest for the C-H bonds of formic acid and formate anion, which do not participate in H-bonding. However, pronounced electron-density transfer from electron lone pairs of the electron donor also leads to reorganization of the electron density in the electron donor, which results in changes in geometry and vibrational frequency. Electron-density transfer from electron lone pairs of the electron donor is directed into sigma* antibonding orbitals of X- H bonds of the electron acceptor and leads to elongation of the bond and a red shift of the X- H stretching frequency (standard H-bonding). This transfer is much larger with the formate anion, for which it exceeds 0.1 e. Formation of a complex is characterized by electron-density transfer from electron donor to ligands.
Tâme Parreira, Renato Luis Galembeck, Sérgio Emanuel Hobza, PavelĬomplexes between formic acid or formate anion and various proton donors (HF, H(2)O, NH(3), and CH(4)) are studied by the MP2 and B3LYP methods with the 6-311++G(3df,3pd) basis set.
On the origin of red and blue shifts of X- H and C-H stretching vibrations in formic acid (formate ion) and proton donor complexes. To support this interpretation, the halogen-bonded complexes glyoxal-BrF and acrolein-BrF are discussed. The comparison with the glyoxal-HF and the acrolein-HF complexes reveals that these blue shifts are a direct consequence of a negative intramolecular coupling between vicinal C dbnd O and C-H bonds in the aldehyde groups of isolated glyoxal and acrolein molecules. It is demonstrated that the calculated blue shifts of the C-H stretching frequencies in the glyoxal- H 2O complexes are only indirectly pertinent to hydrogen bonding to the C-H group.
The structures and the vibrational spectra of the hydrogen-bonded complexes: glyoxal- H 2O, glyoxal-HF, acrolein- H 2O, and acrolein-HF, are investigated within the MP2/aug-cc-pVTZ computational approach. reply-to-post_container only screen and (max-width: 37.The dimers of glyoxal and acrolein with H 2O and HF: Negative intramolecular coupling and blue-shifted C-H stretch Storybreak stars') background-repeat:no-repeat background-position:center}.editor.
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