Hydrogen exchange studies. X. Base-catalyzed isotopic exchange of molecular hydrogen. III. Transition-state vs. initial-state solvation in the dimethyl sulfoxide-water system

1976 ◽  
Vol 98 (3) ◽  
pp. 656-660 ◽  
Author(s):  
E. Buncel ◽  
E. A. Symons
Keyword(s):  
Transition State ◽  
Dimethyl Sulfoxide ◽  
Molecular Hydrogen ◽  
Hydrogen Exchange ◽  
Isotopic Exchange ◽  
Water System ◽  
Initial State

Base-catalyzed Isotopic Exchange of Molecular Hydrogen. II. Rate Dependence on Basicity in the Dimethyl Sulfoxide–Water System

1973 ◽  
Vol 51 (11) ◽  
pp. 1673-1681 ◽  
Author(s):  
E. Allan Symons ◽  
Erwin Buncel
Keyword(s):  
Proton Transfer ◽  
Dimethyl Sulfoxide ◽  
Molecular Hydrogen ◽  
Isotopic Exchange ◽  
Water System ◽  
Medium Composition ◽  
Hydroxide Ion ◽  
Hydride Ion ◽  
Low Sensitivity ◽  
Concerted Reaction

Isotopic exchange of D2 has been determined in mixtures of dimethyl sulfoxide and water under catalysis by hydroxide ion. The rate of exchange increases by ca. 104 as the medium composition is changed from 0% DMSO to 99.6% DMSO at 65 °C. The unusually low sensitivity to medium basicity is reflected in abnormally low slope values for the plots of log kobs υs. H− or J−. When [Me4NOH] is varied at a given medium composition, the apparent order with respect to [Me4NOH] is greater than unity.These results are discussed in terms of (1) rate determining proton transfer from D2 to OH− with formation of hydride ion; (2) a concerted reaction of OH−, D2, and H2O; (3) addition of OH− to D2 to yield an intermediate adduct, [HODD]−; (4) a 6-centered process involving cation participation and electrophilic assistance by H2O in the reaction of OH− with D2.L'échange isotopique de D2 a été étudié dans des mélanges de sulfoxyde de diméthyle et d'eau sous l'effet d'une catalyse par l'ion hydroxyle. Le taux d'échange augmente d'environ 104 alors que la composition du milieu change de 0% en DMSO à 99.6% en DMSO à 65 °C. La sensitivité anormalement faible à la basicité du milieu est réflétée par des valeurs anormalement faibles de la pente dans les graphiques du log kobs υs. H− ou J−. Quand la concentration de Me4NOH est changée pour une composition donnée du milieu, l'ordre apparent en ce qui a trait à la [Me4NOH] est plus élevé que l'unité.

Enhanced reactivity of an α-nucleophile in water-dimethyl sulfoxide mixtures. A transition state effect.

1984 ◽  
Vol 25 (12) ◽  
pp. 1267-1268 ◽  
Author(s):  
Marguerite Laloi-Diard ◽  
Jean-François Verchere ◽  
Patrick Gosselin ◽  
François Terrier
Keyword(s):  
Transition State ◽  
Dimethyl Sulfoxide ◽  
State Effect

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.

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