Synthetic use of the primary kinetic isotope effect in hydrogen atom transfer: generation of α-aminoalkyl radicals

2010 ◽  
Vol 8 (20) ◽  
pp. 4653 ◽  
Author(s):  
Mark E. Wood ◽  
Sabine Bissiriou ◽  
Christopher Lowe ◽  
Andrew M. Norrish ◽  
Katell Sénéchal ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Kinetic Isotope

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.

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