Templated syntheses of cyclic acetylacetone hosts, their affinities for divalent ions, and an example of a slow proton transfer from enol to hydroxide ion

1977 ◽  
Vol 99 (11) ◽  
pp. 3880-3882 ◽  
Author(s):  
Albert H. Alberts ◽  
Donald J. Cram
Keyword(s):  
Proton Transfer ◽  
Divalent Ions ◽  
Hydroxide Ion

Proton transfer from imidazole, benzimidazole, and their 1-alkyl derivatives. FMO analysis of the effect of methyl and benzo substitution

1986 ◽  
Vol 64 (6) ◽  
pp. 1240-1245 ◽  
Author(s):  
Erwin Buncel ◽  
Helen A. Joly ◽  
John R. Jones
Keyword(s):  
Proton Transfer ◽  
Reaction Scheme ◽  
Frontier Molecular Orbital ◽  
Neutral Species ◽  
Ph Profile ◽  
Hydroxide Ion ◽  
Methyl Substitution ◽  
Rate Determining Step ◽  
Alkyl Derivatives ◽  
Conjugate Acid

The rate–pH profile for detritiation from the C-2 position of 1-methylimidazole has been determined in aqueous solution at 85 °C. The profile is consistent with a mechanism involving attack by hydroxide ion on the conjugate acid of the substrate to give an ylid intermediate in the rate-determining step. At higher pH, hydroxide-catalyzed exchange of the neutral species becomes increasingly important. Comparison of the second-order rate constants derived from the rate–pH profiles of imidazole, 1-methylimidazole, benzimidazole, and 1-methylbenzimidazole showed that methyl substitution caused the rate to increase by 2-to 3-fold while benzo annelation increased the rate by 10- to 20-fold. Frontier molecular orbital (FMO) analysis of the reaction scheme for proton transfer from imidazole, benzimidazole, and their 1-alkyl derivatives has been used to explain the rate-accelerating effect of methyl substitution and benzo annelation in these processes.

scholarly journals Hydroxide Ion Carrier for Proton Pumps in Bacteriorhodopsin: Primary Proton Transfer

2020 ◽  
Vol 124 (39) ◽  
pp. 8524-8539
Author(s):  
Junichi Ono ◽  
Minori Imai ◽  
Yoshifumi Nishimura ◽  
Hiromi Nakai
Keyword(s):  
Proton Transfer ◽  
Primary Proton ◽  
Proton Pumps ◽  
Hydroxide Ion ◽  
Ion Carrier

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.

Hydroxide Ion in Liquid Water: Structure, Energetics, and Proton Transfer Using a Mixed Discrete-Continuum ab Initio Model

1995 ◽  
Vol 99 (11) ◽  
pp. 3798-3805 ◽  
Author(s):  
Inaki Tunon ◽  
Daniel Rinaldi ◽  
Manuel F. Ruiz-Lopez ◽  
Jean Louis Rivail
Keyword(s):  
Proton Transfer ◽  
Ab Initio ◽  
Liquid Water ◽  
Water Structure ◽  
Hydroxide Ion

The solvent deuterium isotope effect on the hydroxide-ion-catalyzed conversion of acetaldehyde to its enolate ion

1988 ◽  
Vol 66 (9) ◽  
pp. 2440-2442
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge
Keyword(s):  
Water Molecule ◽  
Proton Transfer ◽  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Solvent Isotope Effect ◽  
Fractionation Factor ◽  
Hydroxide Ion ◽  
Solvent Isotope

Rates of proton transfer from acetaldehyde to the hydroxide ion were measured by iodine scavenging in H2O and in D2O solution at 25 °C; the results give the solvent isotope effect [Formula: see text]. This value is somewhat more consistent with an estimate, made using fractionation factor theory, for hydron transfer directly from the substrate to the hydroxide ion than with another estimate, made similarly, for hydron transfer through an intervening water molecule.

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