Carbocation Formation by Selected Hydrocarbons in Trimethylsulfonium Bromide-AlCl3/AlBr3-HBr Ambient Temperature Molten Salts

Ma, Minhui; Johnson, Keith E.

doi:10.1021/ja00110a007

Cited by 42 publications

(38 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ma and Johnson [10] reported the formation of the parent fluorenium cation (C-2-protonated) in [Me 3 S][Br]/AlBr 3 /HBr (only 1 H NMR spectroscopic data were reported). The present study focuses on the benzannulated derivatives 2-11, from which stable carbocations were generated in FSO 3 H/ SO 2 ClF and in some cases in FSO 3 H/SbF 5 (4:1)/SO 2 ClF, for complete NMR characterization.…”

Section: Resultsmentioning

confidence: 99%

Stable‐Ion NMR and GIAO‐DFT Study of the Carbocations from Benzofluorenes and Dibenzofluorenes; Synthesis of Nitro Derivatives; Mutagenicity Assay and X‐ray Analysis

et al. 2008

View full text Add to dashboard Cite

First examples of stable carbocations are reported from 7H‐benzo[c]fluorene (2), 11H‐benzo[b]fluorene (3), 11H‐benzo[a]fluorene (4), 2‐methoxy‐ (5), 7‐methoxy‐ (6), and 9‐methoxy‐11H‐benzo[a]fluorene (7), 7H‐dibenzo[c,g]fluorene (8), 13H‐dibenzo[a,g]fluorene (9), 2‐methoxy‐13H‐dibenzo[a,g]fluorene (10) and 5,6‐dihydro‐13H‐dibenzo[a,g]fluorene (11). Charge‐delocalization modes in the resulting carbocations were derived based on experimental and/or computed (GIAO‐DFT) Δδ13C values and through the NPA‐derived changes in charges (Δq). Whereas protonation regioselectivity in the parent systems (2, 3, 4, 8, and 9) corresponds to the energetically most favored carbocations computed by DFT, selectivity in the OMe‐substituted derivatives (5, 6, 7, 10, and 11) is strongly controlled by the methoxy group. Benzofluorenes 3, 5, 6, and 7 and dibenzofluorenes 8, and 10 were nitrated under very mild conditions. Nitration selectivity in the parent systems 3 and 8 parallels those in stable‐ion protonation, whereas regioselectivity in the MeO derivatives (6, 7, and 10) corresponds more closely to relative arenium ion energies in the parent unsubstituted systems. Comparative mutagenicity assays (Ames tests) were performed on 3NO2, 5NO2, 7NO2, 8NO2, and 10NO2 relative to their precursors. Compounds 10NO2, 7NO2, and 8NO2 were found to be potent direct‐acting mutagens (with 10NO2, 8NO2 also capable of acting as potent indirect mutagens). The X‐ray structures of 5NO2 and 8NO2 were determined. The angle between the plane of the nitro group and the aromatic ring bearing the NO2 group is 89.4° in 5NO2 and 32.4° in 8NO2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

show abstract

Section: Resultsmentioning

confidence: 99%

Stable‐Ion NMR and GIAO‐DFT Study of the Carbocations from Benzofluorenes and Dibenzofluorenes; Synthesis of Nitro Derivatives; Mutagenicity Assay and X‐ray Analysis

et al. 2008

View full text Add to dashboard Cite

show abstract

“…HA and HD are likely to follow their P.A. values; so depending on the equilibrium constant of Equation (7) [63][64][65] analogous to the formation of ionic/molecular superacid systems from Brønsted and Lewis acid combinations such as SO 3 /SbF 5 /HSO 3 F. [49] …”

Section: Liquid Protic Saltsmentioning

confidence: 99%

Brønsted Acidity and the Medium: Fundamentals with a Focus on Ionic Liquids

2011

Self Cite

View full text Add to dashboard Cite

Fundamental aspects of Brønsted acidity in ionic liquid systems, in relation to those of simple protic molecules in the gas phase, pure protic molecules in the condensed phase and solutions of protic molecules in molecular systems, are presented. The variety of acidities possible, beyond those observed in aqueous systems, is emphasised and discussed in terms of differences of solvent levelling, ionisation, dissociation, homo-/hetero-conjugate ion speciation and the stabilisation of proton-transfer products from solvent to solvent. It is argued that data regarding aqueous systems do not necessarily explain acid/base behaviour in other liquids satisfactorily. Methods of measuring acidity are reviewed, particularly by spectrophotometry and electrochemistry and recommendations proffered for estimating speciation and acidity of ionic liquids of various complexities.

show abstract

“…Chloroaluminate ionic liquid used as the catalyst has been used for alkylation, facilitating separation of ionic liquid and products, having a low reaction temperature and high selectivity of 2-alkylbenzene [1][2][3][4]. For improved control of the reaction process, the catalytic mechanism of chloroaluminate ionic liquid has been extensively reported [5][6][7][8][9][10]. Smith et al [11] found that arene was protonated by [Bmim]Cl-AlCl 3 /HCl, suggesting that the reaction was catalyzed by Bronsted superacidity obtained from the reaction: arene + Al 2 Cl 7  + HCl = arene-H + + 2[AlCl 4 ]  .…”

Section: Introductionmentioning

confidence: 99%