1,721,018 research outputs found
Effect of hydrogen bonding on the methyl conformation of thioacetamide: an ab initio study
No full textMolecular conformation of isolated and hydrogen bonded N,N'-diformohydrazide: an ab initio study
No full textAdsorption of Choline Phenylalanilate on Polyaromatic Hydrocarbon-Shaped Graphene and Reaction Mechanism with CO2: A Computational Study
No full textThe interaction of ionic liquids (ILs) with carbon materials is of fundamental importance in several areas of materials science, physics, and chemistry. Their adsorption on pristine and N-doped graphene surfaces is discussed here on the basis of results of density functional theory calculations. The nature of adsorption was investigated for an amino acid (AA)-based IL consisting of the choline cation [Ch] and the l-phenylalanilate anion [Phe] that interacts with a sheet of N-doped graphene. The interaction mechanism, binding energy, electron density, and non-covalent interaction analysis were evaluated by considering the cation, anion, and ion pair adsorbed on graphene separately. The distribution of cations and anions in the liquid bulk and on the graphene surface was then analyzed by molecular dynamics simulations. Since AA-based ILs are efficient absorbents for capture of CO2 due to the pronounced affinity of carbon dioxide to react with amino groups, we investigated the capacity of [Ch][Phe] to react with CO2 under various conditions. We considered the multistep mechanism of the reaction of [Phe] with CO2 first for the anion in the liquid bulk and then for the [Phe] anion adsorbed on the graphene surface. The initial step, the formation of the zwitterionic addition product, is followed by its structural rearrangement through intramolecular proton transfer and conformational isomerization processes to form carboxylic acid derivatives. The entire mechanism was evaluated for the [Phe] anion before and after adsorption on graphene to investigate how interactions with surfaces of carbon materials can affect the CO2 capture capacity of an AA-based IL such as [Ch][Phe]. © 2023 American Chemical Society
Molecular structure and benzene ring deformation of three cyanobenzenes from gas-phase electron diffraction and quantum chemical calculations
No full textField-induced π-polarization in barrelene derivatives: a computational study based on structural variation
No full textBarrelene, H–C(CH=CH)3C–H, is an unsaturated polycyclic hydrocarbon containing three isolated double bonds in a non-planar arrangement. We have studied the transmission of field effects through the barrelene framework by analyzing the small structural changes occurring in the phenyl group of many Ph–C(CH=CH)3C–X molecules, where X is a variable substituent. Molecular geometries have been determined by quantum chemical calculations at the HF/6-31G* and B3LYP/6-311++G** levels of theory. Comparison with the results obtained for the corresponding saturated molecules, the bicyclo[2.2.2]octane derivatives Ph–C(CH2–CH2)3C–X, reveals a small, but significant, field-induced π-polarization of the barrelene cage, especially when the remote substituent is a charged group. Additional evidence of π-polarization is obtained by comparing the electric dipole moments of the two sets of uncharged molecules. The structural variation of the barrelene cage caused by the variable substituent in Ph–C(CH=CH)3C–X molecules has also been investigated. It is much larger than that of the phenyl group and depends primarily on the electronegativity of the substituent. Particularly pronounced is the concerted variation of the non-bonded distance between the bridgehead carbons of the cage, r(C···C)1BARR, and the average of the three C–C–C angles at the cage carbon bonded to the variable substituent, α1BARR. A scattergram of r(C···C)1BARR versus the corresponding parameter for bicyclo[2.2.2]octane derivatives, r(C···C)1BCO, shows that the variation of r(C···C)1BARR becomes gradually less pronounced than that of r(C···C)1BCO as the electronegativity of the substituent increases
Polar Effects and Structural Variation in 4-Substituted 1-Phenylbicyclo[2.2.2]octane Derivatives: A Quantum Chemical Study
No full textGroup Electronegativities from Benzene Ring Deformations: A Quantum Chemical Study
No full textWe propose a new scale of group electronegativities, derived from benzene ring deformations in Ph-X
molecules. A recent analysis of such deformations (Campanelli, A. R.; Domenicano, A.; Ramondo, F. J.
Phys. Chem. A 2003, 107, 6429) has shown that two orthogonal linear combinations of the internal ring
angles, termed SE and SR, are directly related to the electronegativity and resonance effects of the substituent,
respectively. In the present paper, we show that SE increases linearly with the electronegativity of X within
each of the first two rows of the periodic table, acting as a sensitive indicator of the polarity of the Ph-X
bond. By using SE values from ab initio quantum chemical calculations, we have derived the electronegativities
of 100 organic and inorganic groups. Nonbonded interactions with the ortho hydrogens and carbons may
fictitiously alter the electronegativity of a group; in most cases, however, they are easily eluded by changing
the conformation of the substituent with respect to the benzene ring. Although the atom directly linked to the
ring tends to dominate the electronegativity of a group, the role of its adjacent atoms is also important. Their
effect depends markedly on the nature of chemical bonding and electron density distribution within the group
Transmission of Electronic Substituent Effects through a Benzene Framework: A Computational Study of 4-Substituted Biphenyls Based on Structural Variation
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Structural variations and electronic substituent effects in phenylcubane derivatives: a quantum chemical study
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