Volume 238, 2022

Influence of second-order saddles on reaction mechanisms

Abstract

The transition state, a first-order saddle point on the potential energy surface, plays a central role in understanding the mechanism, dynamics, and rate of chemical reactions. However, we recently identified energetically accessible second-order saddles (SOS) in certain reactions and showed that the SOS plays a crucial role in the dynamics of the reactions [Pradhan et al., Phys. Chem. Chem. Phys., 2019, 21, 12837; Rashmi et al., Regul. Chaotic Dyn., 2021, 26, 119]. In the present work, we investigated the role of second-order saddle points on the dynamics of the thermal denitrogenation of 1-pyrazoline using ab initio classical trajectory simulations at the CASSCF(4,4)/6-31+G* level of theory, for total energies of 130, 140, and 150 kcal mol−1 available to the system. In this unimolecular dissociation reaction, the SOS point is 4 kcal mol−1 higher in energy than the synchronous bond-breaking transition state and opens up an additional reaction pathway. We found that the fraction of molecules following the synchronous bond-breaking pathway decreased with an increase in the total available energy in the reaction, accompanied by an increase in the fraction following the asynchronous pathway. To further understand the competition between the transition state and the SOS pathways, we investigated the mechanism of halogen-substituted 1-pyrazolines where the SOS energies are comparable to that of the transition states.

Graphical abstract: Influence of second-order saddles on reaction mechanisms

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
31 jan 2022
Accepted
04 mar 2022
First published
04 mar 2022

Faraday Discuss., 2022,238, 183-203

Influence of second-order saddles on reaction mechanisms

K. Yadav, R. Pradhan and U. Lourderaj, Faraday Discuss., 2022, 238, 183 DOI: 10.1039/D2FD00026A

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