Direct dynamics calculation of the kinetic isotope effect for an organic hydrogen-transfer reaction, including corner-cutting tunneling in 21 dimensions

1993 ◽  
Vol 115 (17) ◽  
pp. 7806-7817 ◽  
Author(s):  
Yi Ping Liu ◽  
Da Hong Lu ◽  
Angels Gonzalez-Lafont ◽  
Donald G. Truhlar ◽  
Bruce C. Garrett
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydrogen Transfer ◽  
Transfer Reaction ◽  
Corner Cutting ◽  
Direct Dynamics ◽  
Hydrogen Transfer Reaction ◽  
Kinetic Isotope ◽  
Dynamics Calculation

Kinetic isotope effect and tunnelling in the proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent

1979 ◽  
Vol 57 (6) ◽  
pp. 669-672 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Deuterium Isotope Effect ◽  
Kinetic Isotope ◽  
Enthalpy Of Activation ◽  
Entropy Of Activation ◽  
Large Primary

The proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent shows a large primary deuterium isotope effect, kH/kD = 24.3 at 0 °C and 16.9 at 20 °C. The enthalpy of activation difference (ΔHD≠ − ΔHH≠) = 2.6 ± 0.4 kcal mol−1 and the entropy of activation difference (ΔSD≠ − ΔSH≠) = 3.4 ± 1.3 cal mol−1 K−1. This isotope effect, when fitted to Bell's equation, indicates that there is a considerable contribution to this reaction from tunnelling of the proton through the potential energy barrier.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1085-1096 ◽  
Author(s):  
A M Kuznetsov ◽  
Jens Ulstrup
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Rate Constants ◽  
Bovine Serum ◽  
Kinetic Isotope Effect ◽  
Hydrogen Transfer ◽  
Low Frequency ◽  
Specific Rate ◽  
Adiabatic Limits ◽  
Kinetic Isotope

We discuss a broad theoretical frame for hydrogen transfer in chemical and biological systems. Hydrogen tunnelling, coupling between the tunnel modes and the environment, and fluctuational barrier preparation for hydrogen tunnelling are in focus and given precise analytical forms. Specific rate constants are provided for three limits, i.e., the fully diabatic, the partially adiabatic, and the fully adiabatic limits. These limits are all likely to represent real chemical or biological hydrogen transfer systems. The rate constants are referred particularly to the driving force and temperature dependence of the kinetic isotope effect (KIE). The origin of these correlations is different in the three limits. It is rooted in the tunnel factor and weak excitation of the heavier isotopes in the former two limits, giving a maximum for thermoneutral processes. A new observation is that the adiabatic limit also accords with a KIE maximum for thermoneutral processes but the KIE is here reflected solely in the activation Gibbs free energy differences, in this case rooted in the low-frequency environmental nuclear dynamics. Three systems of biological hydrogen tunnelling, viz. lipoxygenase, yeast alcohol dehydrogenase, and bovine serum amine oxygenase, offer unusual new cases for analysis and have been analysed using the theoretical frames. All the systems show large KIEs and strong indications of hydrogen tunnelling. They also represent different degrees of fluctuational barrier preparation, with lipoxygenase as the most rigid and bovine serum amine oxygenase as the softest system.Key words: generalized Born-Oppenheimer scheme, kinetic isotope effect, gated proton transfer, partially adiabatic proton transfer, proton tunnelling in enzyme catalysis.

scholarly journals Evidence for tunneling in base-catalyzed isomerization of glyceraldehyde to dihydroxyacetone by hydride shift under formose conditions

2015 ◽  
Vol 112 (14) ◽  
pp. 4218-4220 ◽  
Author(s):  
Liang Cheng ◽  
Charles Doubleday ◽  
Ronald Breslow
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydrogen Transfer ◽  
Hydrogen Atom Transfer ◽  
Hydride Shift ◽  
Kinetic Isotope ◽  
Isomerization Mechanism ◽  
The Difference ◽  
Intrinsic Kinetic ◽  
Quantitative Hplc

Hydrogen atom transfer reactions between the aldose and ketose are key mechanistic features in formose chemistry by which formaldehyde is converted to higher sugars under credible prebiotic conditions. For one of these transformations, we have investigated whether hydrogen tunneling makes a significant contribution to the mechanism by examining the deuterium kinetic isotope effect associated with the hydrogen transfer during the isomerization of glyceraldehyde to the corresponding dihydroxyacetone. To do this, we developed a quantitative HPLC assay that allowed us to measure the apparent large intrinsic kinetic isotope effect. From the Arrhenius plot of the kinetic isotope effect, the ratio of the preexponential factors AH/AD was 0.28 and the difference in activation energies Ea(D) − Ea(H) was 9.1 kJ·mol−1. All these results imply a significant quantum-mechanical tunneling component in the isomerization mechanism. This is supported by multidimensional tunneling calculations using POLYRATE with small curvature tunneling.

Correction to “Direct-Dynamics VTST Study of the [1,7] Hydrogen Shift in 7-Methylocta-1,3-(Z),5(Z)-triene. A Model System for the Hydrogen Transfer Reaction in Previtamin D3”

2011 ◽  
Vol 115 (33) ◽  
pp. 9322-9324
Author(s):  
S. Hosein Mousavipour ◽  
Antonio Fernández-Ramos ◽  
Rubén Meana-Pañeda ◽  
Emilio Martínez-Nuñez ◽  
Saulo A. Vázquez ◽  
...  
Keyword(s):  
Hydrogen Transfer ◽  
Transfer Reaction ◽  
Model System ◽  
Hydrogen Shift ◽  
Direct Dynamics ◽  
Hydrogen Transfer Reaction
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