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An Experimentally Established Key Intermediate in Benzene Nitration with Mixed Acid
Author(s) -
Koleva Gergana,
Galabov Boris,
Hadjieva Boriana,
Schaefer Henry F.,
Schleyer Paul von R.
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201506959
Subject(s) - nitration , chemistry , benzene , photochemistry , electrophile , potential energy surface , molecule , ion , electrophilic aromatic substitution , reaction mechanism , computational chemistry , electronic structure , organic chemistry , catalysis
Experimental evidence is reported for the first intermediate in the classic S E Ar reaction of benzene nitration with mixed acid. The UV/Vis spectroscopic investigation of the reaction showed an intense absorption at 320 nm (appearing as a band shoulder) arising from a reaction intermediate. Our theoretical modeling shows that the interaction between the two principal reactants with solvent (H 2 SO 4 ) molecules significantly affects the structure of the initial complex. In this complex, a larger distance between the aromatic ring and nitronium ion precludes the possibility for electronic charge transfer from the benzene π‐system to the electrophile. The computational modeling of the potential energy surface reveals that the reaction favors a stepwise mechanism with intermediate formation of π‐ and σ‐ (arenium ion) complexes.