Ping-pong tunneling reactions, part 2: boron and carbon bell-clapper rearrangement

Anthracene can be used as a scaffold for intramolecular S 2 degenerate reactions of the “bell clapper” type, where a central boron atom or its isoelectronic carbocation bonds alternatively towards one or the other lateral Lewis bases at the first and eight anthracene positions. This ping-pong bond-s...

Full description

Saved in:
Bibliographic Details
Published inPure and applied chemistry Vol. 92; no. 1; pp. 39 - 47
Main Authors Nandi, Ashim, Sucher, Adam, Tyomkin, Anat, Kozuch, Sebastian
Format Journal Article
LanguageEnglish
Published Berlin De Gruyter 01.01.2020
Walter de Gruyter GmbH
Subjects
Anthracene
bell-clapper reaction
Boron
computational chemistry
Cryogenic temperature
ICPOC-24
Isotopes
kinetic isotope effect
kinetics
NMR
NMR spectroscopy
quantum tunneling
Quantum tunnelling
Online AccessGet full text

Cover

More Information
Summary:Anthracene can be used as a scaffold for intramolecular S 2 degenerate reactions of the “bell clapper” type, where a central boron atom or its isoelectronic carbocation bonds alternatively towards one or the other lateral Lewis bases at the first and eight anthracene positions. This ping-pong bond-switching reaction possesses a symmetrical double-well potential with low activation barrier and relatively narrow barrier width. Herein we show by computational means the active role played by heavy atom quantum tunneling in this degenerate rearrangement reaction at cryogenic temperatures. At these conditions the thermal “over the barrier” reaction is forbidden, whereas the tunneling effect enhances the rate of reaction up to an experimentally measurable half-life. Kinetic isotope effects and cryogenic NMR spectroscopy can, in principle, experimentally demonstrate the tunneling mechanism.
ISSN:0033-4545
1365-3075
DOI:10.1515/pac-2019-0401