Issue 25, 2022

Perceptions on the treatment of apparent isotope effects during the analyses of reaction rate and mechanism

Abstract

Isotope substitution, a fascinating tool of physical chemistry, has been broadly applied in the research field of heterogeneous catalysis. In general, due to the differences in the mass-related atomic vibrational frequencies and zero-point energy of isotopic molecules, the apparent isotope effect (AIE) or observed kinetic isotope effect (observed KIE) from isotope substitution examination could provide unique knowledge regarding the reaction rate and mechanism of a catalytic reaction, such as the rate-determining step, key reaction intermediate, or catalyst design and synthesis. However, the treatment of the AIE is not as straightforward as the isotopic switch experiment, and needs sufficient care and comprehensive identification to deal with the influences from the equilibrium isotope effects (EIEs) of quasi-equilibrium elementary steps, kinetic isotope effect (KIE) of the pseudo rate-determining step, transition states, intrinsic reaction barriers, etc. Fundamentally, the key factors affecting the AIE could be the partition function part and the zero-point energy part of each single elementary step. Theoretically, the classification of the KIE could be based on the quantity of KIE (including normal KIE and inverse KIE) or the molecular transformation (including primary KIE, secondary KIE, tunneling KIE, and solvent KIE) involved. This article presents a recap of the fundamental concepts and relations of KIE, EIE and AIE, and a concise review on the selected applications of isotope effects throughout heterogeneous catalysis. Lastly, the meaningful perspectives regarding the critical factors that impact the AIE and the appropriate treatment of the AIE are discussed meticulously.

Graphical abstract: Perceptions on the treatment of apparent isotope effects during the analyses of reaction rate and mechanism

  • This article is part of the themed collection: PCCP Reviews

Article information

Article type
Perspective
Submitted
18 Ots. 2022
Accepted
21 Mai. 2022
First published
24 Mai. 2022

Phys. Chem. Chem. Phys., 2022,24, 15182-15194

Perceptions on the treatment of apparent isotope effects during the analyses of reaction rate and mechanism

X. Gao, X. Yu and C. Chang, Phys. Chem. Chem. Phys., 2022, 24, 15182 DOI: 10.1039/D2CP00825D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements