- Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity
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Dodecavanadate, [V12O32]4? (V12), possesses a 4.4 ? cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12O32(Br2)]4? (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm?1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n-butane, and n-pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3-bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2-,3-dibromobutane and 2,3-dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes.
- Hayashi, Yoshihito,Inada, Yasuhiro,Katayama, Misaki,Kikukawa, Yuji,Kitajima, Hiromasa,Seto, Kensuke,Watanabe, Daiki,Yamashita, Shohei
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supporting information
p. 14399 - 14403
(2020/07/13)
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- Efficient Conversion of Alkyl Chlorides into Bromides
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The convenient and selective catalytic conversion of secondary and tertiary alkyl chlorides into bromides with hydrogen bromide in the presence of small amounts of anhydrous iron(III) bromide is described.
- Yoon, K. B.,Kochi, J. K.
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p. 1013 - 1014
(2007/10/02)
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- Free Radical Substitution. Part 38. The Effect of Solvent on the Atomic Chlorination and Bromination of 2-Substituted Butanes and the Importance of Steric Effects
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The relative selectivity of atomic halogenation of 2-substituted butanes is influenced by the phase and by solvents.There are solvents which increase the selectivity compared with the gas phase and solvents which decrease the relative selectivity.However the most striking feature of the halogenation (especially the bromination) of 2-substituted butanes is the high reactivity of the 2-position notwithstanding very unfavourable polar effects.This reactivity is attributed to the release of steric compression associated with the abstraction of the tertiary hydrogen atom.The halogenation of butan-2-ol esters is associated with some decomposition of 2-butyl radical (OCOR)CH3> and the chlorination of 2-phenylbutane with the formation of olefins 2-phenylbut -1-ene and 2-phenylbut-2-ene.
- Atto, Saeed Y.,Tedder, John M.,Walton, John C.
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p. 629 - 634
(2007/10/02)
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- Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 4. A Stereochemical Probe for the Existence and the Relative Stability of Cyclic Halonium Ions in the Gas Phase
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A comprehensive investigation on the existence and the relative stability of gaseous three-membered cyclic butene halonium ions was carried out by establishing the stereochemistry of the acid-induced displacement by nucleophilic such as H2O, H2S, etc., on a number of positively charged intermediates.The latter were obtained in the gas phase from the reaction of radiolytic formed Broensted (CH5+ and C2H5+) and Lewis (C2H5+ and CH3FCH3+) acids with 2,3-dihalobutanes.The stereoisomeric distribution of the neutral 3-halobutan-2-ols (or thiols) formed in these processes strongly implies the intermediacy of cyclic 2,3-butene halonium ions, whose stability in the gas phase depends on the nature of the halogen involved, increasing in passing from Cl to Br.No evidence for the occurrence of stable cyclic 2,3-butene fluoronium ions was obtained by the same procedure.Other factors, namely the strength of the radiolytic gaseous acid "catalysts" and the configuration of the starting dihalobutane, were found to play a role in determining the stereochemistry of the substitution processes investigated.A close correspondence does exist between the present results and those from strictly related mass spectrometric and condensed phase investigation.
- Angelini, Giancarlo,Speranza, Maurizio
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p. 3792 - 3799
(2007/10/02)
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- Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 5. Quantitative Evaluation of Neighboring-Group Participation in Bifunctional Compounds
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A previous radiolytic study on the stereochemistry of gas-phase nuclephilic displacement on several classes of positively charged intermediates, formed from the attack of gaseous acids (CH5+, C2H5+, CH3FCH3+, etc.) on suitable substrates, is now completed with the assessment of the detailed mechanism and the relative extent of the other major reaction pathways accompanying them.The analysis of the stereoisomeric distribution of the neutral end products allows a quantitative evaluation of the gas-phase neighboring-group participation in such systems.A participating-group ability trend of OH >> Br >/= Cl is found, which is appreciably dependent on the nature of the leaving group and the configuration of the starting substrate.The evaluation of the adjacent-group "effective concentration" in these gaseous systems provides the first direct evidence for a gas-phase anchimerically assisted ionic reaction, involving a three-membered ring formation.The results obtained in the gas phase differ significantly from those concerning related solvolytic processes.
- Angelini, Giancarlo,Speranza, Maurizio
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p. 3800 - 3806
(2007/10/02)
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