Ab initio molecular orbital calculations on hydrogen bonding in binary water-alcohol mixtures: (CH3OH)2(H2O), (CH3OH) (H2O)2, and (CF3CH2OH)(H2O)

2009 ◽  
Vol 20 (S15) ◽  
pp. 189-197
Author(s):  
L. A. Curtiss ◽  
D. J. Frurip
Keyword(s):  
Hydrogen Bonding ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Alcohol Mixtures ◽  
Water Alcohol

Ion-specificity for hydrogen-bonding hydration of polymer: an approach by ab initio molecular orbital calculations II

2001 ◽  
Vol 574 (1-3) ◽  
pp. 195-211 ◽  
Author(s):  
Hajime Muta ◽  
Tesong Sin ◽  
Akira Yamanaka ◽  
Susumu Kawauchi ◽  
Mitsuru Satoh
Keyword(s):  
Hydrogen Bonding ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Ion Specificity

Amino and cyano N atoms in competitive situations: which is the best hydrogen-bond acceptor? A crystallographic database investigation

2001 ◽  
Vol 57 (6) ◽  
pp. 850-858 ◽  
Author(s):  
Nahossé Ziao ◽  
Jérôme Graton ◽  
Christian Laurence ◽  
Jean-Yves Le Questel
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Amino Nitrogen ◽  
Lone Pair ◽  
Molecular Surface ◽  
Molecular Orbital Calculations ◽  
Hydrogen Bond Acceptor

The relative hydrogen-bond acceptor abilities of amino and cyano N atoms have been investigated using data retrieved from the Cambridge Structural Database and via ab initio molecular orbital calculations. Surveys of the CSD for hydrogen bonds between HX (X = N, O) donors, N—T—C≡N (push–pull nitriles) and N—(Csp 3) n —C≡N molecular fragments  show that the hydrogen bonds are more abundant on the nitrile than on the amino nitrogen. In the push–pull family, in which T is a transmitter of resonance effects, the hydrogen-bonding ability of the cyano nitrogen is increased by conjugative interactions between the lone pair of the amino substituent and the C≡N group: a clear example of resonance-assisted hydrogen bonding. The strength of the hydrogen-bonds on the cyano nitrogen in this family follows the experimental order of hydrogen-bond basicity, as observed in solution through the pK HB scale. The number of hydrogen bonds established on the amino nitrogen is greater for aliphatic aminonitriles N—(Csp 3) n —C≡N, but remains low. This behaviour reflects the greater sensitivity of the amino nitrogen to steric hindrance and the electron-withdrawing inductive effect compared with the cyano nitrogen. Ab initio molecular orbital calculations (B3LYP/6-31+G** level) of electrostatic potentials on the molecular surface around each nitrogen confirm the experimental observations.

A pairwise additivity scheme for conformational energies of substituted ethanes

1975 ◽  
Vol 343 (1632) ◽  
pp. 1-10 ◽  
Keyword(s):  
Large Deviations ◽  
Ab Initio ◽  
Dihedral Angle ◽  
Molecular Orbital ◽  
Methyl Groups ◽  
Molecular Orbital Calculations ◽  
Linear Combinations ◽  
Strongly Interacting ◽  
Conformational Energies

Ab initio molecular orbital calculations are used to explore additivity in the conformational energies of poly-substituted ethanes in terms of conformational energies of ethane and appropriate mono- and 1,2-di-substituted derivatives. Such relations would allow complex calculations for poly-substituted ethanes to be replaced by much simpler ones on a small number of parent molecules. General expressions for the linear combinations are derived from the assumption that interactions between vicinal substituents are pairwise additive and depend only on the vicinal dihedral angle. The additivity scheme is tested for 15 ethanes, di-, tri- or tetrasubstituted by cyano and methyl groups and for a smaller number of fluoroethanes. Additivity applies to within 0.1- 0.3 k J mol -1 in the methylethanes and mostly to within about 0.7- 0.8 kJ mol -1 in cyanoethanes. Large deviations are found among the geminally substituted fluoroethanes. It is suggested that the additivity approximation is most successful in the absence of strongly interacting geminal groups. Predictions are made of conformational energies of ten hexa(cyano- and methyl-) substituted ethanes.

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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