Formation and characterization of the radical cation of pentamethylbenzyl trifluoroacetate from the oxidation of hexamethyl (Dewar benzene) by thallium(<scp>III</scp>) trifluoroacetate in trifluoroacetic acid—a slow and complex reaction

Eberson, Lennart; Hartshorn, Michael P.; Persson, Ola; Svensson, Jan‐Olof

doi:10.1039/p29950001253

Cited by 6 publications

(4 citation statements)

References 40 publications

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“…8 The mechanism of the reaction was suggested to be similar to that for oxidation with mercury() as shown in Scheme 2, 8 but Eberson has proposed that the mechanism is more complex. 9 Arylthallium() radical cations 7 ϩ have never been directly observed in these reactions, but the reaction of anthracene gives rise to the spectrum of the radical cations of 9-trifluoroacetoxyand 9,10-bis(trifluoroacetoxy)anthracene, 10-12 benzo[a]pyrene, 7-methylbenzo[a]pyrene, and 12-methylbenzo[a]pyrene show the spectrum of the radical cations of the 7-and/or 12-trifluoroacetates, 13 and triptycene (9,10-dihydro-9,10-[1,2]benzenoanthracene) shows a spectrum which was ascribed to the radical cation of tris(trifluoroacetoxy)triptycene, 12 and it was suggested that these trifluoroacetates might be formed via the thalliated intermediate 7 (Scheme 2). The 199 Hg satellites were obscured by lines due to proton coupling.…”

Section: Introductionmentioning

confidence: 99%

An EPR study of electron transfer reactions involving arenes and mercury(II) or thallium(III) salts

Davies¹,

Ng²

1998

J. Chem. Soc., Perkin Trans. 2

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Section: Introductionmentioning

confidence: 99%

An EPR study of electron transfer reactions involving arenes and mercury(II) or thallium(III) salts

Davies¹,

Ng²

1998

J. Chem. Soc., Perkin Trans. 2

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“…A 13-line EPR spectrum with hyperfine splitting constant of 0.98 mT was assigned [ 1031 to the 2B2 state of 36+, but as pointed out later [104], other interpretations are also possible. The reaction between Dewar benzene and TTFA in TFAH is investigated in detail by Eberson et al [105]. It is proposed that the reaction involves a slow acid-catalyzed conversion of 36 into hexamethyl benzene (HMB) which is then oxidized by TTFA to pentamethylbenzyl trifluoroacetate 37.…”

Section: 28mentioning

confidence: 99%

Electron‐transfer Reactions of Aromatic Compounds

Gescheidt¹,

Khan²

2001

Electron Transfer in Chemistry

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Aromatic molecules are inclined to undergo electron-transfer reactions. The additional charges introduced by the electron-transfer process are efficiently stabilized by delocalization. Nevertheless rearrangements of the molecular skeleton or followup reactions can occur. The course of the electron-transfer reactions and the properties of the species thus formed are the subject of this section.In particular, we concentrate on the species formed after an one-electron transfer reaction. Starting from closed-shell diamagnetic precursors, paramagnetic stages, i.e. radical cations or radical anions are formed in this first step. To understand the properties and reactivity of these species, detailed knowledge in terms of charge and spin delocalization and electronic structure is an important prerequisite. This information is preferably derived from electronic and paramagnetic resonance (EPR and electron-nuclear multiple resonance-techniques such as ENDOR or Triple spectroscopy). It has recently been shown that the experimental results can be substantiated by the use of quantum-chemical calculations. In addition to Hartree-Fock-based ab initio procedures, calculations on the density-functional level of theory have been established as rather efficient tools. Therefore, before representing examples of electron-transfer-generated radicals a short survey of the computational methods is given.Another substantial factor directing the kinetic and thermodynamic stability of charged radicals is ion pairing. This phenomenon, although well established for many years, is often not directly distinct in experiments. To establish the importance of ion pairing, or, in other words, supramolecular interactions, a separate introductory chapter is dedicated to these aspects.The references are selected particularly from recent publications, without, however, ignoring some 'classical' contributions. In some sections topics are included which do not strictly represent aromatic molecules but involve interactions of ztype orbitals.

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“…Eberson and co-workers, [205][206][207][208][209][210][211] as well as Davies and coworkers [212][213][214][215][216] have used 4-tolyl thallium(III)-bis(trifluoroacetate) and TTFA for the generation of stable radical cations. Juliá and co-workers have also studied the behaviour of the system TTFA/TFA for the generation of radical cations from 2,2'-bithienyl 217,218 and 2,2'-bifuranyl derivatives, 219 as well as for polymers preparation.…”

Section: Scheme 82mentioning

confidence: 99%