A large kinetic isotope effect in the reaction of ascorbic acid with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in aqueous buffer solutions

Ikuo Nakanishi; Yoshimi Shoji; Kei Ohkubo; Toshihiko Ozawa; Ken Ichiro Matsumoto; Shunichi Fukuzumi

doi:10.1039/d0cc05214k

A large kinetic isotope effect in the reaction of ascorbic acid with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in aqueous buffer solutions

Ikuo Nakanishi, Yoshimi Shoji, Kei Ohkubo, Toshihiko Ozawa, Ken Ichiro Matsumoto, Shunichi Fukuzumi

Department of Chemistry & Nanoscience

Research output: Contribution to journal › Article › peer-review

14 Scopus citations

Abstract

A large kinetic isotope effect (KIE,k_H/k_D) of 12.8 was observed for the hydrogen-transfer reaction from ascorbic acid to 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in a phosphate buffer solution (0.05 M, pH/pD 7.0) at 298 K. The isotopic difference in the activation energies (6.8 kJ mol⁻¹) determined from the temperature dependence of the KIE suggests that quantum mechanical tunneling may partly play a role in the reaction, although the isotopic ratio of the Arrhenius prefactor (A_H/A_D= 0.86) is within the semiclassical limits.

Original language	English
Pages (from-to)	11505-11507
Number of pages	3
Journal	Chemical Communications
Volume	56
Issue number	77
DOIs	https://doi.org/10.1039/d0cc05214k
State	Published - 4 Oct 2020

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© The Royal Society of Chemistry 2020.

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title = "A large kinetic isotope effect in the reaction of ascorbic acid with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in aqueous buffer solutions",

abstract = "A large kinetic isotope effect (KIE,kH/kD) of 12.8 was observed for the hydrogen-transfer reaction from ascorbic acid to 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in a phosphate buffer solution (0.05 M, pH/pD 7.0) at 298 K. The isotopic difference in the activation energies (6.8 kJ mol−1) determined from the temperature dependence of the KIE suggests that quantum mechanical tunneling may partly play a role in the reaction, although the isotopic ratio of the Arrhenius prefactor (AH/AD= 0.86) is within the semiclassical limits.",

author = "Ikuo Nakanishi and Yoshimi Shoji and Kei Ohkubo and Toshihiko Ozawa and Matsumoto, {Ken Ichiro} and Shunichi Fukuzumi",

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year = "2020",

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doi = "10.1039/d0cc05214k",

language = "English",

volume = "56",

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T1 - A large kinetic isotope effect in the reaction of ascorbic acid with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in aqueous buffer solutions

AU - Nakanishi, Ikuo

AU - Shoji, Yoshimi

AU - Ohkubo, Kei

AU - Ozawa, Toshihiko

AU - Matsumoto, Ken Ichiro

AU - Fukuzumi, Shunichi

PY - 2020/10/4

Y1 - 2020/10/4

N2 - A large kinetic isotope effect (KIE,kH/kD) of 12.8 was observed for the hydrogen-transfer reaction from ascorbic acid to 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in a phosphate buffer solution (0.05 M, pH/pD 7.0) at 298 K. The isotopic difference in the activation energies (6.8 kJ mol−1) determined from the temperature dependence of the KIE suggests that quantum mechanical tunneling may partly play a role in the reaction, although the isotopic ratio of the Arrhenius prefactor (AH/AD= 0.86) is within the semiclassical limits.

AB - A large kinetic isotope effect (KIE,kH/kD) of 12.8 was observed for the hydrogen-transfer reaction from ascorbic acid to 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in a phosphate buffer solution (0.05 M, pH/pD 7.0) at 298 K. The isotopic difference in the activation energies (6.8 kJ mol−1) determined from the temperature dependence of the KIE suggests that quantum mechanical tunneling may partly play a role in the reaction, although the isotopic ratio of the Arrhenius prefactor (AH/AD= 0.86) is within the semiclassical limits.

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U2 - 10.1039/d0cc05214k

DO - 10.1039/d0cc05214k

M3 - Article

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AN - SCOPUS:85092088701

SN - 1359-7345

VL - 56

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EP - 11507

JO - Chemical Communications

JF - Chemical Communications

IS - 77

ER -

A large kinetic isotope effect in the reaction of ascorbic acid with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO˙) in aqueous buffer solutions

Abstract

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