scholarly journals Ab Initio Calculation of Thermodynamic and Kinetic Quantities for 1,3-Dipolar Cycloadditions of Benzonitrile Oxide with Various Dipolarophiles

2002 ◽  
Vol 2002 (6) ◽  
pp. 279-281 ◽  
Author(s):  
E. Rajaian ◽  
M. Monajjemi ◽  
M.R. Gholami
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Rate Constant ◽  
Thermodynamic Stability ◽  
Ab Initio Calculation ◽  
Transition States ◽  
Molecular Orbital Calculations ◽  
Free Energies ◽  
Energy Calculations ◽  
Dipolar Cycloadditions

Ab initio molecular orbital calculations have been used to investigate the structures and transition states of 1,3-dipolar cycloadditions between benzonitrile oxide with ethylene, acrylonitrile, tetracyanoethylene and cyclopentene. Geometry optimisations and energy calculations were performed with RHF/6–31G*//RHF/6–31G* in each case. Calculation of vibrational frequencies permitted computation of the enthalpies, Gibbs free energies and rate constant of reactions. Cycloadditions of 1,3-dipolar benzonitrile oxide with electron-poor dipolarophiles have higher rates and lower thermodynamic stability than with other dipolarophiles.

Ab initio molecular orbital study of simple 1,3-dipolar reactions

1976 ◽  
Vol 29 (3) ◽  
pp. 465 ◽  
Author(s):  
D Poppinger
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Transition States ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Extended Basis ◽  
Optimized Geometries

Ab initio molecular orbital calculations with minimal and extended basis sets have been carried out for the 1,3-dipolar addition of fulminic acid to acetylene, ethylene, ethynamine and propynenitrile. Optimized geometries are reported for the transition states HCNO+C2H2, HCNO+C2H4, HCNO+ C2HNH2, for the adducts isoxazole and 2-isoxazoline, and for nitrosocyclopropene as a possible intermediate. The calculations indicate that (a) these 1,3-dipolar reactions are synchronous processes, (b) the geometry of the transition state is insensitive to substitution and (c) of the isomeric substituted adducts, 5-aminoisoxazole and isoxazole-4-carbonitrile should be formed preferentially.

Ab Initio Study of Solvent Effects on Rate of 1,3-Dipolar Cycloadditions of Benzonitrile Oxide and Various Dipolarophiles

2003 ◽  
Vol 2003 (2) ◽  
pp. 91-95 ◽  
Author(s):  
E. Rajaeian ◽  
M. Monajjemi ◽  
M.R. Gholami
Keyword(s):  
Hydrogen Bonding ◽  
Oxygen Atom ◽  
Water Molecule ◽  
Ab Initio ◽  
Solvent Effects ◽  
Transition States ◽  
Molecular Orbital Calculations ◽  
Interaction Energies ◽  
Ab Initio Study ◽  
Dipolar Cycloadditions

Ab initio molecular orbital calculations have been used to investigate the structures and the transition states of 1,3-dipolar cycloadditions between benzonitrile oxide with ethylene, cyclopentene, acrylonitrile and tetracyanoethylene in heptane and water: calculations reveal enhanced hydrogen bonding of a water molecule to the transition states for the cycloaddition 1,3-dipolar of reaction of benzonitrile oxide with cyclopentene, the optimal interaction energies being 0.7 kcal/mol more favourable for hydrogen bonding to the oxygen atom in the transition states than for the reactants.

Ab initio molecular orbital calculations on thirene: The thermodynamic stability of five C2H2S isomers

1978 ◽  
Vol 53 (2) ◽  
pp. 211-214 ◽  
Author(s):  
O.P. Strausz ◽  
R.K. Gosavi ◽  
F. Bernardi ◽  
P.G. Mezey ◽  
J.D. Goddard ◽  
...  
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Thermodynamic Stability ◽  
Molecular Orbital Calculations

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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