Issue 28, 2020

Large transition state stabilization from a weak hydrogen bond

Abstract

A series of molecular rotors was designed to study and measure the rate accelerating effects of an intramolecular hydrogen bond. The rotors form a weak neutral O–H⋯O[double bond, length as m-dash]C hydrogen bond in the planar transition state (TS) of the bond rotation process. The rotational barrier of the hydrogen bonding rotors was dramatically lower (9.9 kcal mol−1) than control rotors which could not form hydrogen bonds. The magnitude of the stabilization was significantly larger than predicted based on the independently measured strength of a similar O–H⋯O[double bond, length as m-dash]C hydrogen bond (1.5 kcal mol−1). The origins of the large transition state stabilization were studied via experimental substituent effect and computational perturbation analyses. Energy decomposition analysis of the hydrogen bonding interaction revealed a significant reduction in the repulsive component of the hydrogen bonding interaction. The rigid framework of the molecular rotors positions and preorganizes the interacting groups in the transition state. This study demonstrates that with proper design a single hydrogen bond can lead to a TS stabilization that is greater than the intrinsic interaction energy, which has applications in catalyst design and in the study of enzyme mechanisms.

Graphical abstract: Large transition state stabilization from a weak hydrogen bond

Supplementary files

Article information

Article type
Edge Article
Submitted
15 May 2020
Accepted
02 Jul 2020
First published
02 Jul 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 7487-7494

Large transition state stabilization from a weak hydrogen bond

E. C. Vik, P. Li, J. M. Maier, D. O. Madukwe, V. A. Rassolov, P. J. Pellechia, E. Masson and K. D. Shimizu, Chem. Sci., 2020, 11, 7487 DOI: 10.1039/D0SC02806A

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