On the conformational behavior of dimethyl carbonate

Bohets, Hugo; Veken, B.J. van der

doi:10.1039/a901046g

Cited by 60 publications

(71 citation statements)

References 15 publications

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“…[23] The main conclusion from all the previous work is that the gas phase consists of a mixture of the cis,cis and cis,trans conformers in which the cis,cis predominates. Ab initio calculations show that there is also a slightly higher energy near trans,trans conformer with the methyl groups slightly above and below the molecular plane.…”

Section: Methanediol and Dimethoxymethanementioning

confidence: 94%

Ligand Close Packing, Molecular Compactness, the Methyl Tilt, Molecular Conformations, and a New Model for the Anomeric Effect

Gillespie

Robinson

Pilmé

2010

Chemistry A European J

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All the atoms in a molecule attract each other until they reach their equilibrium positions at which point the repulsive forces between the atoms just balance the attractive forces and there are no resultant forces acting on any of the atoms in the molecule. Thus, we can consider that in the equilibrium geometry the atoms in a molecule are arranged as compactly as possible. This is the basis of the ligand close packing (LCP) model according to which three or four monatomic ligands X, such as F, Cl or O (formally =O or O(-)) pack as closely as possible around a small central atom such as a boron or carbon atom giving a truly close-packed equilateral triangular AX(3) molecule or a tetrahedral AX(4) molecules. Such monatomic ligands can, to a good approximation, be described as having a spherical shape with a single ligand radius r(X). In contrast, ligands with donor atoms with lone pairs such as the oxygen atom in an OX group have a less symmetrical electron density requiring two ligand radii, r(O(lp)) in the lone pair direction, and r(O(b)) in the bonding direction, where r(O(lp)) < r(O(b)) for an approximate description. On this basis we propose an explanation for the "methyl tilt", in methanol and many related molecules, and in conjunction with the concept of compactness, a model for explaining the relative energies of the conformations of molecules containing OH and OMe ligands, including molecules that exhibit the anomeric effect. We compare our model for the anomeric effect with the widely accepted "hyperconjugation" model. We also discuss the relationship between the concept of compactness and the concept of hardness.

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Section: Methanediol and Dimethoxymethanementioning

confidence: 94%

Ligand Close Packing, Molecular Compactness, the Methyl Tilt, Molecular Conformations, and a New Model for the Anomeric Effect

Gillespie

Robinson

Pilmé

2010

Chemistry A European J

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“…For ethyl formate, propyl formate, and dimethyl carbonate, vibrational mode data were obtained from Refs. [21][22][23] respectively.…”

Section: A Introductionmentioning

confidence: 99%

Interplay between permanent dipole moments and polarizability in positron-molecule binding

et al. 2012

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Energy-resolved studies of positron-molecule collisions exhibit vibrational Feshbach resonances in annihilation, thus providing evidence that positrons can bind to these species. The downshifts of the observed resonances from the positions of the vibrational modes provides a measure of the positron-molecule binding energies, which range from 1 to 300 meV. Reported here are annihilation spectra and binding energies for a wider range of chemical species than studied previously, including aldehydes, ketones, formates, acetates, and nitriles. While the measured binding energies show an approximate correlation with molecular dipole polarizability and permanent dipole moment, other effects are important for dipole moments 2.0 D. For these compounds, it appears that localization of the positron wave function near a portion of the molecule leads to enhanced binding and an increased dependence on both the molecular dipole moment and the electron-positron correlations. The relationship of these results to theoretical calculations is discussed.

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“…The intensive absorption at 1,293 cm -1 could be assigned to the m as (O-C-O) vibration. Kar et al [46] and Bohets and van der Veken [47] used a similar assignation for identifying the absorption bands obtained after DMC adsorption. In the 2,000 and 1,100 cm -1 region in the spectra of MF adsorbed on Cu/Norit between peaks were detected at 1,768, 1,754 and 1,743 cm -1 and a weak absorption was observed at 1,208 cm -1 .…”

Section: Drift Spectra Registered During the Reactionmentioning

confidence: 99%

The Synthesis of Dimethyl Carbonate by the Oxicarbonylation of Methanol Over Cu Supported on Carbon Norit

et al. 2014

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The catalytic activity of Norit supported Cu, Ni and Cu-Ni catalysts was investigated in the synthesis of dimethyl carbonate (DMC) by the oxidative carbonylation of methanol. Cu/Norit showed the best catalytic activity. The reaction was carried out in a continuous flow system at atmospheric pressure usually at 393 K. The main products were methyl formate, DMC and CO 2 . The methanol conversion on Cu/Norit achieved in steady state was about 22 % and the DMC yield 13.2 %. Based on the XPS data we can establish that copper reduced to its metallic form during reduction but oxidized in the reaction mixture, and is mostly in the Cu ? state, with some Cu 2? . It is possible that the DMC formation rate depends on the surface concentration of oxidized Cu and on the ratio of Cu ? and Cu 2? . Based upon the IR measurements adsorbed DMC was found on the surface of the Cu/Norit catalyst during the catalytic reaction.

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On the conformational behavior of dimethyl carbonate

Cited by 60 publications

References 15 publications

Ligand Close Packing, Molecular Compactness, the Methyl Tilt, Molecular Conformations, and a New Model for the Anomeric Effect

Ligand Close Packing, Molecular Compactness, the Methyl Tilt, Molecular Conformations, and a New Model for the Anomeric Effect

Interplay between permanent dipole moments and polarizability in positron-molecule binding

The Synthesis of Dimethyl Carbonate by the Oxicarbonylation of Methanol Over Cu Supported on Carbon Norit

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