Catalytic Mechanism of Dihydrofolate Reductase Enzyme. A Combined Quantum-Mechanical/Molecular-Mechanical Characterization of Transition State Structure for the Hydride Transfer Step

1999 ◽  
Vol 121 (51) ◽  
pp. 12140-12147 ◽  
Author(s):  
R. Castillo ◽  
J. Andrés ◽  
V. Moliner
Keyword(s):  
Transition State ◽  
Dihydrofolate Reductase ◽  
Catalytic Mechanism ◽  
Mechanical Characterization ◽  
Hydride Transfer ◽  
Quantum Mechanical ◽  
State Structure ◽  
Transition State Structure ◽  
Transfer Step

Topological aspects of chemical reactivity. On the possible use of similarity index in characterizing the transition state structure in concerted pericyclic reactions

1987 ◽  
Vol 52 (6) ◽  
pp. 1375-1385
Author(s):  
Robert Ponec
Keyword(s):  
Transition State ◽  
Chemical Reactivity ◽  
Transition States ◽  
Similarity Index ◽  
Pericyclic Reactions ◽  
State Structure ◽  
Transition State Structure ◽  
Topological Similarity

The use of the topological similarity index as a simple means for classification and characterization of the structure of the transition states in concerted pericyclic reactions is discussed. The suggested formulation makes it possible to bring a quantitative aspects into the empirical Dewar's classification of transition states in terms of aromaticity and/or antiaromaticity.

Hydride transfer reactions. A kinetic study of oxidation of 2- and 3-methoxy-N-methylacridans by some π acceptors and a one-electron oxidant

1984 ◽  
Vol 62 (9) ◽  
pp. 1780-1784 ◽  
Author(s):  
Allan K. Colter ◽  
Peter Plank ◽  
John P. Bergsma ◽  
Roy Lahti ◽  
André A. Quesnel ◽  
...  
Keyword(s):  
Transition State ◽  
Kinetic Study ◽  
Radical Cation ◽  
Hydride Transfer ◽  
Transfer Reactions ◽  
State Structure ◽  
Transition State Structure ◽  
Hydride Transfer Reactions ◽  
The One

Relative rates of oxidation of N-methylacridan (1a), 2-methoxy-N-methylacridan (1b), and 3-methoxy-N-methylacridan (1c) have been investigated as a probe of transition state structure in hydride transfer reactions. Oxidants investigated cover a 2 × 107-fold (with 1a) to 2 × 108-fold (with 1c) range of reactivity, and include the π acceptors 1,4-benzoquinone (BQ), p-chloranil (CA), 2,3-dicyano-1,4-benzoquinone (DCBQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE) in acetonitrile (AN), BQ in 50:50 (v/v) AN–water, and the one-electron oxidant tris(2,2′-bipyridyl)cobalt-(III), [Formula: see text], in AN, all at 25 °C. For all of the π acceptors except TCNE the order of reactivity, 1c > 1b > 1a, (DH) indicates a transition state resembling the corresponding acridinium ion product (D+), while the order of reactivity with [Formula: see text], 1b > 1c > 1a, indicates a transition state resembling the acridan radical cation [Formula: see text]. The order of reactivity observed with TCNE, 1b > 1c > 1a, is tentatively interpreted as indicating a transition state resembling the corresponding 9-acridanyl radical (D•).

Mechanism and transition-state structure of hydride-transfer reactions mediated by nad(p)h-models

Tetrahedron ◽  
1986 ◽  
Vol 42 (4) ◽  
pp. 975-992 ◽  
Author(s):  
J.W. Verhoeven ◽  
W. van Gerresheim ◽  
F.M. Martens ◽  
S.M. van der Kerk
Keyword(s):  
Transition State ◽  
Hydride Transfer ◽  
Transfer Reactions ◽  
State Structure ◽  
Transition State Structure ◽  
Hydride Transfer Reactions
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