Barrier to Rotation about the Phenyl−Carbonyl Carbon Bond of Methyl Benzoate by Dynamic NMR Spectroscopy and ab Initio Molecular Orbital Calculations

2000 ◽  
Vol 65 (5) ◽  
pp. 1552-1553 ◽  
Author(s):  
Diwakar M. Pawar ◽  
Kanyetta K. Wilson ◽  
Eric A. Noe
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Methyl Benzoate ◽  
Molecular Orbital Calculations ◽  
Dynamic Nmr ◽  
Carbonyl Carbon ◽  
Carbon Bond ◽  
Dynamic Nmr Spectroscopy

A theoretical study of adduct formation between methanolate and Propan-2-one

1981 ◽  
Vol 34 (6) ◽  
pp. 1189 ◽  
Author(s):  
JC Sheldon
Keyword(s):  
Hydrogen Bond ◽  
Oxygen Atom ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Theoretical Study ◽  
Adduct Formation ◽  
Molecular Orbital Calculations ◽  
Carbonyl Carbon ◽  
Methyl Group ◽  
Methoxide Anion

Ab initio molecular orbital calculations at the STO-3G level of approximation predict that the methoxide anion bonds through its oxygen atom to form complexes with acetone in at least three different ways: (i) A tetrahedral adduct at the carbonyl carbon (ΔE -262 kJ mol-1). (ii) A hydrogen-bond complex with a single hydrogen of one methyl group (- 100 kJ mol-1). (iii) A symmetrical bidentate hydrogen-bond complex with a hydrogen from each acetone methyl group (- 143 kJ mol-1).

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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