How amino and nitro substituents direct electrophilic aromatic substitution in benzene: an explanation with Kohn-Sham molecular orbital theory and Voronoi deformation density analysis

Olga Stasyuk , Halina Szatyłowicz , Tadeusz Marek Krygowski , C. Fonseca Guerra

Abstract

The substituent effect of the amino and nitro groups on the electronic system of benzene has been investigated quantum chemically using quantitative Kohn–Sham molecular orbital theory and a corresponding energy decomposition analysis (EDA). The directionality of electrophilic substitution in aniline can accurately be explained with the amount of contribution of the 2pz orbitals on the unsubstituted carbon atoms to the highest occupied π orbital. For nitrobenzene, the molecular π orbitals cannot explain the regioselectivity of electrophilic substitution as there are two almost degenerate π orbitals with nearly the same 2pz contributions on the unsubstituted carbon atoms. The Voronoi deformation density analysis has been applied to aniline and nitrobenzene to obtain an insight into the charge rearrangements due to the substituent. This analysis method identified the orbitals involved in the C–N bond formation of the π system as the cause for the π charge accumulation at the ortho and para positions in the case of the NH2 group and the largest charge depletion at these same positions for the NO2 substituent. Furthermore, we showed that it is the repulsive interaction between the πHOMO of the phenyl radical and the πHOMO of the NH2 radical that is responsible for pushing up the πHOMO of aniline and therefore activating this π orbital of the phenyl ring towards electrophilic substitution.
Author Olga Stasyuk (FC / DPC)
Olga Stasyuk,,
- Department Of Physical Chemistry
, Halina Szatyłowicz (FC / DPC)
Halina Szatyłowicz,,
- Department Of Physical Chemistry
, Tadeusz Marek Krygowski
Tadeusz Marek Krygowski,,
-
, C. Fonseca Guerra
C. Fonseca Guerra,,
-
Journal seriesPhysical Chemistry Chemical Physics, ISSN 1463-9076, (A 40 pkt)
Issue year2016
Vol18
No17
Pages11624-11633
Publication size in sheets0.5
ASJC Classification1606 Physical and Theoretical Chemistry; 3100 General Physics and Astronomy
DOIDOI:10.1039/C5CP07483E
URL http://pubs.rsc.org/en/Content/ArticleLanding/2016/CP/c5cp07483e#!divAbstract
Project[2013/11/B/ST4/00531 POLON ] Towards physical interpretation of the substituent effect. Project leader: Szatyłowicz Halina, , Phone: (22) 234-7755 w. 106, start date 22-08-2014, Implemented
WCh Projects financed by NSC [Projekty finansowane przez NCN]
Languageen angielski
File
c5cp07483e.pdf 3.96 MB
Score (nominal)40
ScoreMinisterial score = 40.0, 05-09-2019, ArticleFromJournal
Ministerial score (2013-2016) = 40.0, 05-09-2019, ArticleFromJournal
Publication indicators Scopus Citations = 15; WoS Citations = 16; Scopus SNIP (Source Normalised Impact per Paper): 2016 = 1.117; WoS Impact Factor: 2016 = 4.123 (2) - 2016=4.242 (5)
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