1-butyl-3-methylimidazolium-trifluoromethanesulfonate and trifluoromethanesulfonic-acid

In contrast to previous reactions carried out in cyclopentane solvent at room temperature that produced 6-TfO-B10H13 (TfO = CF3SO3), the reaction of closo-B10H10(2-) with a large excess of trifluoromethanesulfonic acid in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate (bmimOTf) gave exclusively the previously unknown 5-TfO-B10H13 isomer. Experimental and computational studies demonstrated that the difference in the products of the two reactions is a result of 6-TfO-B10H13 isomerizing to 5-TfO-B10H13 above room temperature in bmimOTf solutions. Reactivity studies showed that 5-TfO-B10H13: (1) is deprotonated by reaction with 1,8-bis(dimethylamino)naphthalene to form the 5-TfO-B10H12(1-) anion; (2) reacts with alcohols to produce 6-RO-B10H13 boryl ethers (R = Me and 4-CH3O-C6H4); (3) undergoes olefin-hydroboration reactions to form 5-TfO-6,9-R2-B10H11 derivatives; and (4) forms a 5-TfO-6,9-(Me2S)2-B10H11 adduct at its Lewis acidic 6,9-borons upon reaction with dimethylsulfide. The 5-TfO-6,9-(Me2S)2-B10H11 adduct was also found to undergo alkyne-insertion reactions to form a range of previously unreported triflate-substituted 4-TfO-ortho-carboranes (1-R-4-TfO-1,2-C2B10H10) and reactions with triethylamine or ammonia to form the first TfO-substituted decaborate [R3NH(+)]2[2-TfO-B10H9(2-)], and [R3NH(+)]2[1-TfO-B10H9(2-)] (R = H, Et) salts.

Topics: Imidazoles; Ionic Liquids; Mesylates; Models, Molecular; Molecular Structure; Quantum Theory

The activity, stability and conformation of laccase were first investigated in an aqueous solution of ionic liquids 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim]TfO), 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([Bmpyr]TfO) or tetramethylammonium trifluoromethanesulfonate ([TMA]TfO). Compared with control system, high level of [Bmim]TfO or [Bmpyr]TfO destabilizes laccase while [TMA]TfO stabilizes laccase. These effects are more pronounced with the extension of the incubation time. The activity variations are well correlated with the changes of the conformation of laccase evidenced by fluorescence and circular dichroism spectra under specified conditions. The effects of the three ionic liquids on laccase are associated with the chaotropicity of the cations in Hofmeister series. For laccase, [TMA]TfO is not a good activating agent but it greatly enhances the stability of laccase in addition to maintaining the catalytic efficiency of laccase, showing its great potential in real application.

Topics: Circular Dichroism; Enzyme Stability; Guanidine; Hydrogen-Ion Concentration; Imidazoles; Ionic Liquids; Kinetics; Laccase; Least-Squares Analysis; Mesylates; Nonlinear Dynamics; Protein Conformation; Protein Denaturation; Regression Analysis; Spectrometry, Fluorescence; Time Factors; Trametes