2016
DOI: 10.1021/acs.accounts.6b00120
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Electrophilic Aromatic Substitution: New Insights into an Old Class of Reactions

Abstract: The classic SEAr mechanism of electrophilic aromatic substitution (EAS) reactions described in textbooks, monographs, and reviews comprises the obligatory formation of arenium ion intermediates (σ complexes) in a two-stage process. Our findings from several studies of EAS reactions challenge the generality of this mechanistic paradigm. This Account focuses on recent computational and experimental results for three types of EAS reactions: halogenation with molecular chlorine and bromine, nitration by mixed acid… Show more

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Cited by 161 publications
(148 citation statements)
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“…The direct substitution mechanism consists of a single concerted reaction step, in which the hydrogen transfer from HCl to Cl 2 and from the aromatic compound to HCl takes place. The addition–elimination mechanism, as proposed by Galabov, Schleyer and co‐workers, involves three steps. The first step is an addition of Cl 2 to the aromatic ring.…”
Section: Introductionmentioning
confidence: 99%
“…The direct substitution mechanism consists of a single concerted reaction step, in which the hydrogen transfer from HCl to Cl 2 and from the aromatic compound to HCl takes place. The addition–elimination mechanism, as proposed by Galabov, Schleyer and co‐workers, involves three steps. The first step is an addition of Cl 2 to the aromatic ring.…”
Section: Introductionmentioning
confidence: 99%
“…H-ZSM-5, 12 C-benzene/ethanol and 13 C-benzene/ethanol were purchased from ACS materials, Sigma Aldrich and Cambridge Isotope Laboratories, respectively. Catapal D (alumina) was received from Sasol.…”
Section: Methodsmentioning
confidence: 99%
“…Furthermore, this reaction is also of academic interest, as the underlying mechanistic principles of S E Ar are currently the subject of debate. According to a few recent studies, the classical Wheland intermediate is not always considered to be an obligatory intermediate during S E Ar [10][11][12][13] . Thus, the objectives of this work are to investigate the S E Ar mechanism at the solid/gas interface of a heterogeneous catalyst, and to resolve the ambiguity about the involvement of Wheland intermediates in zeolite-catalysed S E Ar reactions.…”
mentioning
confidence: 99%
“…The electrophilic addition to the aromatic is assumed to give an alkyl cyclohexadienyl cation, also known as a Wheland intermediate or σ-complex (Fig. 1), although an alternative concerted additionelimination pathway without the formation of the intermediate carbocation has been proposed for some cases 8 . As confirmed by Weckhuysen and colleagues for the ethylation of benzene, the active electrophile on zeolites is the ethyl group directly bonded to framework oxygen (that is, the ethoxy group) resulting from the reaction of ethanol or ethylene with the Brønsted acid (Fig.…”
Section: Teresa Blascomentioning
confidence: 99%