The electrophilic aromatic bromination of benzenes: mechanistic and regioselective insights from density functional theory

Research output: Contribution to journalArticlepeer-review

Abstract

The HBr-assisted electrophilic aromatic bromination of benzene, anisole and nitrobenzene was investigated using static DFT calculations in gas phase and implicit apolar (CCl4) and polar (acetonitrile) solvent models at the ωB97X-D/cc-pVTZ level of theory. The reaction profiles corresponding to either a direct substitution reaction or an addition-elimination process were constructed and insight into the preferred regioselectivity was provided using a combination of conceptual DFT reactivity indices, aromaticity indices, Wiberg bond indices and the non-covalent interaction index. Our results show that under the considered reaction conditions the bromination reaction preferentially occurs through an addition-elimination mechanism and without formation of a stable charged Wheland intermediate. The ortho/para directing effect of the electron-donating methoxy-group in anisole was ascribed to a synergy between strong electron delocalisation and attractive interactions. In contrast, the preferred meta-addition on nitrobenzene could not be traced back to any of these effects, nor to the intrinsic reactivity property of the reactant. In this case, an electrostatic clash between the ipso-carbon of the ring and the nitrogen atom resulting from the later nature of the rate-determining step, with respect to anisole, appeared to play a crucial role.

Original languageEnglish
Pages (from-to)28581-28594
Number of pages14
JournalPhysical Chemistry Chemical Physics
Volume25
Issue number42
DOIs
Publication statusPublished - 1 Sep 2023

Bibliographical note

Funding Information:
The authors gratefully acknowledge the Research Foundation-Flanders for the financial support through a research grant (G024019N). FDP also wishes to thank the Vrije Universiteit Brussel (VUB) for the support to his research group through a strategic research program. XD wishes to thank Jochen Eeckhoudt for the very fruitful brainstorming discussions. VVS acknowledges funding from the Research Board of the Ghent University. All computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government. The graphical representations of the geometries were obtained using the freely available CYLview software.57

Funding Information:
The authors gratefully acknowledge the Research Foundation-Flanders for the financial support through a research grant (G024019N). FDP also wishes to thank the Vrije Universiteit Brussel (VUB) for the support to his research group through a strategic research program. XD wishes to thank Jochen Eeckhoudt for the very fruitful brainstorming discussions. VVS acknowledges funding from the Research Board of the Ghent University. All computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation – Flanders (FWO) and the Flemish Government. The graphical representations of the geometries were obtained using the freely available CYLview software.57

Publisher Copyright:
© 2023 The Royal Society of Chemistry.

Fingerprint

Dive into the research topics of 'The electrophilic aromatic bromination of benzenes: mechanistic and regioselective insights from density functional theory'. Together they form a unique fingerprint.

Cite this