The effect of the base strength upon the structure of the transition state in E2 reactions. Kinetics of eliminations from 2-arylethyltrimethylammonium bromides promoted by sodium phenoxide and sodium m-nitrophenoxide in N,N-dimethylformamide

1977 ◽  
Vol 42 (2) ◽  
pp. 205-207 ◽  
Author(s):  
Sergio Alunni ◽  
Enrico Baciocchi ◽  
Piero Perucci
Keyword(s):  
Transition State ◽  
Base Strength ◽  
Kinetics Of

THE ALKALINE CLEAVAGE OF o-NITROBENZYLTRIMETHYLSILANE SOLVENT EFFECTS IN THE DIOXANE–WATER SYSTEM

1963 ◽  
Vol 41 (6) ◽  
pp. 1525-1530 ◽  
Author(s):  
H. R. Allcock
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Water System ◽  
Solvent Polarity ◽  
High Water ◽  
Aqueous Dioxane ◽  
Alkaline Cleavage ◽  
Rate Of Reaction ◽  
Kinetics Of

The kinetics of alkaline cleavage of o-nitrobenzyltrimethylsilane were examined in aqueous dioxane media. At high water concentrations, increases in solvent polarity retard the cleavage, as required by a mechanism involving charge dispersion in the transition state. At high dioxane concentrations, solvent polarity increases are accompanied by increases in the rate of reaction, a result which may reflect association between the solvent components.

Nucleophilic participation of incoming ligands in the transition state of substitution reactions of aquocobalamin: kinetics of the reaction with imidazole and its derivatives

1990 ◽  
Vol 170 (1) ◽  
pp. 134
Author(s):  
Helder M. Marques ◽  
Timothy J. Egan ◽  
John H. Marsh ◽  
John R. Mellor ◽  
Orde Q. Munro
Keyword(s):  
Transition State ◽  
Substitution Reactions ◽  
Kinetics Of

Kinetics of the reduction of nicotinonitrile cations by 1,4-dihydronicotinamides

1985 ◽  
Vol 63 (6) ◽  
pp. 1245-1249 ◽  
Author(s):  
John W. Bunting ◽  
John C. Brewer
Keyword(s):  
Ionic Strength ◽  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Spectral Studies ◽  
Close Correspondence ◽  
Charge Generation ◽  
Kinetic Isotope ◽  
Hammett Σ Constants ◽  
Kinetics Of

The rates of reduction of a series of 1-(Z-benzyl)nicotinonitrile cations by a series of 1-(X-benzyl)-1,4-dihydronicotinamides have been studied at 25 °C in 20% CH3CN – 80% H2O (pH 7.0 (5 mM phosphate), ionic strength 1.0 (KCl)). Spectral studies indicate the formation of 1,4-dihydronicotinonitrile products, without the formation of the isomeric 1,2-dihydro- or 1,6-dihydro-nicotinamide intermediates. Second-order rate constants (k2) for these reductions are closely correlated with the Hammett σ constants for X and Z. Thus, for X = H, log k2 = 0.63σz − 1.05, while for Z = 4-CN, log k2 = −0.64σx − 0.65. The close correspondence between these ρx and ρz values indicates that charge neutralization on the nicotinonitrile cation exactly balances charge generation on the nicotinamide cation product in the rate-determining transition state. Thus the migrating hydrogen species is electrically neutral in the rate-determining transition state, which contrasts with the hydridic transition states previously reported in the reduction of isoquinolinium cations by 1,4-dihydronicotinamides. When 1-benzyl-4,4-dideuterio-1,4-dihydronicotinamide is used as the reductant, primary kinetic isotope effects of 3.0 and 2.7 are observed for the reduction of the 1-methylnicotinonitrile and 1-(4-cyanobenzyl)-nicotinonitrile cations, respectively. These data are evaluated in terms of the various mechanistic possibilities for hydride transfer.

Kinetic medium effects. IV. Transition state activity coefficients in mixed solvents

1972 ◽  
Vol 25 (4) ◽  
pp. 777 ◽  
Author(s):  
PT McTigue ◽  
AR Watkins
Keyword(s):  
Transition State ◽  
Activity Coefficients ◽  
Mixed Solvents ◽  
State Theory ◽  
Medium Effects ◽  
State Activity ◽  
Medium Activity ◽  
Solvent Systems ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of acid hydrolysis of a number of aliphatic acetals have been studied in dimethyl sulphoxide-water and dioxan-water mixtures. Where possible, experimentally measured medium activity coefficients for the acetals in the solvent systems have been used in order to calculate the transition state activity coefficients as a function of solvent composition. These activity coefficients are compared with those calculated for the transition states of other hydrolytic reactions, and with the known activity coefficients of some stable ions. The results show no features inconsistent with the assumptions of transition state theory.

Reaction kinetics of hydrogen atom abstraction from isopentanol by the H atom and HO2˙ radical

2018 ◽  
Vol 20 (16) ◽  
pp. 10895-10905
Author(s):  
Prajakta Rajaram Parab ◽  
K. Alexander Heufer ◽  
Ravi Xavier Fernandes
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Reaction Kinetics ◽  
Hydrogen Atom Abstraction ◽  
Abstraction Reaction ◽  
Kinetics Of ◽  
Ho2 Radical

The formation of the transition state for the H-abstraction reaction from isopentanol by the HO2˙ radical.

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