Quantum chemical study on low energy reaction path for

The semi-empirical quantum-chemical PCILO method has been used for calculation of the energy surface of the proton transfer along the O-H...N hydrogen bond in acetic acid-imidazole . 2 H2O system. The PCILO calculations gave the energy surface with two minima. The most stable minimum corresponds to the O-H...N hydrogen bond and has been found at the distances RH...N = 0.149 nm and RO...N = 0.107 nm. According to the PCILO calculations the proton transfer is accompanied by significant changes in the O...N distance. The second energy minimum corresponding to the proton transfer O-...NH+ complex has been found at RH...N = 0.10 nm and RO...N = 0.30 nm. The approximative minimum energy reaction path for the proton transfer has been calculated by the procedure developed by Muller and Brown. The calculated energy barrier represents a value 376.15 kJ/mol. The second energy minimum lies higher by 246 kJ/mol.

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On the Walk Rearrangement of Cyclopentadienylphosphanes and Related Compounds - A Molecular Orbital Study

Zeitschrift für Naturforschung B ◽

10.1515/znb-1983-1216 ◽

1983 ◽

Vol 38 (12) ◽

pp. 1635-1642 ◽

Cited By ~ 9

Author(s):

Wolfgang W. Schoeller

Keyword(s):

Quantum Chemical ◽

Quantum Chemical Study ◽

Chemical Study ◽

Low Energy ◽

State Structure ◽

Transition State Structure ◽

Frontier Orbitals ◽

Orbital Symmetry ◽

Molecular Orbital Study ◽

Related Compounds

The walk rearrangement of cyclopentadienylphosphanes and related compounds is analyzed on the basis of a quantum chemical study. Although according to orbital symmetry considerations the reaction takes place with retention of configuration (at the migrating atom), inversion of configuration is also feasible. Low energy barriers for the walk reaction are expected if (a) radical stabilizing groups are attached to the cyclopentadienyl unit, (b) the fragment MR2 (migrating group) exerts strong radical stabilizing ability and (c) possesses energetically high lying frontier orbitals. The final goal, the device of a molecular structure which freezes in the transition state structure is discussed

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Study of the Electrochemically Initiated Cyanomethylation of Azomethines by Means of the MNDO and AM1 Semiempirical Methods

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19952028 ◽

1995 ◽

Vol 60 (12) ◽

pp. 2028-2038

Author(s):

Jaromír Toušek ◽

Jaro Komenda ◽

Ulrich Hess

Keyword(s):

Quantum Chemical ◽

Radical Anion ◽

Main Product ◽

Reaction Path ◽

Activation Enthalpy ◽

Quantum Chemical Study ◽

Chemical Study ◽

Stationary Points ◽

Semiempirical Methods ◽

Reaction Step

The semiempirical methods (MNDO and AM1) have been used in the quantum chemical study of electrochemically initiated cyanomethylation of azomethines. Reaction steps leading to the main product of the studied reaction, β-aminonitrile, have been described. The stationary points on the reaction path have been found and the activation enthalpies of reaction steps have been determined. Three possible mechanisms for the abstraction of a proton from acetonitrile have been described (by azomethine radical anion, by β-aminonitrile anion, and by hydrogenated azomethine anion). At the MNDO level, the abstraction of a proton by azomethine radical anion has the highest activation enthalpy (∆H = 197 kJ mol-1) and the abstraction of a proton by hydrogenated azomethine anion has the lowest activation enthalpy (∆H = 146 kJ mol-1). The activation enthalpy of the next reaction step (the reaction of acetonitrile anion with azomethine) is low compared to the activation enthalpies of the previous reation steps (∆H= 12 kJ mol-1).

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