An Experimentally Established Key Intermediate in Benzene Nitration with Mixed Acid. Issue 47 (25th September 2015)

• Record Type: Journal Article
• Authors: Koleva, Gergana; Galabov, Boris; Hadjieva, Boriana; Schaefer, Henry F.; Schleyer, Paul von R.
• Is Part Of: Angewandte Chemie international edition. Volume 54:Issue 47(2015)
• Page Start: 14123
• Page End: 14127
• Publication Date: 2015-09-25
• Subjects: aromatic electrophilic substitution -- density functional computations -- nitration -- reaction mechanisms; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201506959
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Experimental evidence is reported for the first intermediate in the classic SE 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 (H2 SO4 ) 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. Abstract : A new intermediate in an old reaction : Experimental evidence is presented for the first intermediate in benzene nitration with mixed acid. Both experiment and theory show that no charge transfer accompanies the formation of the π‐complex. EOM=Equation of motion.