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Purushottam Haldar - One of the best experts on this subject based on the ideXlab platform.

  • viscosities of Tetrabutylammonium Bromide sodium tetraphenylborate and sodium Bromide in 2 ethoxyethanol water mixed solvent media at 308 15 313 15 318 15 and 323 15 k
    Journal of Molecular Liquids, 2008
    Co-Authors: Purushottam Haldar
    Abstract:

    Abstract The viscosities of the solutions of Tetrabutylammonium Bromide (Bu4NBr), sodium tetraphenylborate (NaBPh4), sodium Bromide (NaBr) in 2-ethoxyethanol + water mixed solvent media containing 0.25, 0.50 and 0.75 mass fractions of 2-ethoxyethanol (w1) have been reported at 308.15, 313.15, 318.15, and 323.15 K. The viscosity data have been analyzed by the Jones–Dole equation for the associated electrolytes to evaluate the viscosity B-coefficients of the electrolytes. These data have also been analyzed by the transition-state treatment to obtain contribution of the solutes to the free energy of activation for viscous flow of the solution. The viscosity of the solvent is found to be greatly modified by the presence of the Tetrabutylammonium, tetraaphenylborate and Bromide ions; sodium ion, on the other hand, is not such efficient in modifying the viscosity of the media investigated. Moreover, these ions behave neither as structure-breaker nor as structure-maker and the formation of the transition-state is made less favorable in their presence in aqueous 2-ethoxyethanol solutions.

  • electrical conductances of Tetrabutylammonium Bromide and tetrapentylammonium Bromide in 2 ethoxyethanol water mixtures at 308 15 313 15 318 15 and 323 15 k
    Physics and Chemistry of Liquids, 2008
    Co-Authors: Purushottam Haldar
    Abstract:

    The electrical conductances of the solutions of Tetrabutylammonium Bromide (Bu4NBr), and tetrapentylammonium Bromide (Pen4NBr) in 2-ethoxyethanol (1) + water (2) mixed solvent media containing 0.25, 50 and 0.75 mass fractions of 2-ethoxyethanol (w 1) have been reported at 308.15, 313.15, 318.15 and 323.15 K. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ0), the association constant (K A) and the association diameter (R). These two electrolytes are found to exist essentially as free ions in the solvent mixtures with w 1 = 0.25 and 0.50 over the entire temperature range; however, slight ionic association was observed in the mixed solvent medium richest in 2-ethoxyethanol. The electrostatic ion–solvent interaction is found to be very weak for the tetraalkylammonium ions in the aqueous 2-ethoxyethanol mixtures investigated.

  • electrical conductances of Tetrabutylammonium Bromide sodium tetraphenylborate and sodium Bromide in 2 ethoxyethanol in the temperature range 35 50 c
    Zeitschrift für Physikalische Chemie, 2004
    Co-Authors: Purushottam Haldar
    Abstract:

    The electrical conductances of the solutions of Tetrabutylammonium Bromide (Bu 4 NBr), sodium tetraphenylborate (NaPh 4 B) and sodium Bromide (NaBr) in 2-ethoxyethanol have been reported at 35, 40, 45 and 50°C. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance (Λ 0 ), the association constant (K Λ ) and the association diameter (R). The ionic contributions to the limiting molar conductances (Λ 0 ) have been estimated using the "reference electrolyte" Tetrabutylammonium tetraphenylborate (Bu 4 NPh 4 B). Appreciable ionic association was observed for all of these electrolytes which were found to exist in the form of solvent-separated ion-pairs in 2-ethoxyethanol. The Tetrabutylammonium and tetraphenylborate ions are found to remain scarcely solvated whereas the sodium and Bromide ions undergo substantial solvation in 2-ethoxyethanol medium in the temperature range investigated here.

Michael North - One of the best experts on this subject based on the ideXlab platform.

  • cr salophen complex catalyzed cyclic carbonate synthesis at ambient temperature and pressure
    ACS Catalysis, 2016
    Co-Authors: Jose A Castroosma, Katie J Lamb, Michael North
    Abstract:

    The combination of a chromium(III) salophen Bromide complex and Tetrabutylammonium Bromide is shown to catalyze the reaction between terminal epoxides and carbon dioxide at ambient temperature and 1 bar carbon dioxide pressure and between internal epoxides and carbon dioxide at 80 °C and 10 bar carbon dioxide pressure to form cyclic carbonates. The optimal conditions involve the use of 1.5–2.5 mol % of both the chromium(III) salophen Bromide complex and Tetrabutylammonium Bromide and result in the formation of cyclic carbonates in 57–92% isolated yields after a reaction time of 24 h. Under these conditions, no polycarbonate formation is observed except when cyclohexene oxide is used as substrate. The reactions were found to proceed with retention of epoxide stereochemistry. A study of the reaction kinetics revealed that the chromium(III) complex and Tetrabutylammonium Bromide react together to form a six-coordinate anionic chromium complex which is the actual catalyst, and a catalytic cycle is proposed wh...

  • synthesis of oxazolidinones from epoxides and isocyanates catalysed by aluminium heteroscorpionate complexes
    Chemcatchem, 2016
    Co-Authors: Jose A Castroosma, Amy Earlam, Agustin Larasanchez, Antonio Otero, Michael North
    Abstract:

    The combination of an aluminium(heteroscorpionate) complex and Tetrabutylammonium Bromide acts as a highly efficient catalyst system for the synthesis of oxazolidinones from epoxides and isocyanates. Twenty two complexes were tested derived from a range of bispyrazole ligands and containing 1-3 aluminium atoms per complex. The optimal catalyst was found to be a bimetallic complex of a thioacetamidate ligand. Under the optimal reaction conditions (80°C in toluene for 24h using 5mol% of both aluminium catalyst and Tetrabutylammonium Bromide co-catalyst), six epoxides were reacted with six aromatic isocyanates, giving 25 oxazolidinones in moderate to excellent yields showing broad substrate scope. The regiochemistry of the reaction (to produce 3,4- or 3,5-oxazolidinones) is controlled by the substrate with epoxide ring opening occurring preferentially at the less hindered end of the epoxide unless a substituent on the epoxide can stabilise a positive charge.

  • influence of temperature and pressure on cyclic carbonate synthesis catalyzed by bimetallic aluminum complexes and application to overall syn bis hydroxylation of alkenes
    Journal of Organic Chemistry, 2013
    Co-Authors: Christopher Beattie, Michael North, Pedro Villuendas, Carl Young
    Abstract:

    The effect of moderate temperatures (22–100 °C) and pressures (1–10 bar) on the synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by a combination of bimetallic aluminum complexes and Tetrabutylammonium Bromide is investigated. The combined bimetallic complex and Tetrabutylammonium Bromide catalyst system is shown to be an order of magnitude more active than the use of Tetrabutylammonium Bromide alone at all temperatures and pressures studied. At the higher temperatures and pressures used, disubstituted epoxides become substrates for the reaction and it is shown that reactions proceed with retention of the epoxide stereochemistry. This allowed a route for the overall syn-bis-hydroxylation of alkenes to be developed without the use of hazardous metal based reagents. At higher pressures it is also possible to use compressed air as the carbon dioxide source.

Biswajit Sinha - One of the best experts on this subject based on the ideXlab platform.

  • effect of Tetrabutylammonium Bromide on solution behavior of salicylaldehyde anil zinc ii in methanol at t 298 15 308 15 and 318 15 k
    The Journal of Chemical Thermodynamics, 2013
    Co-Authors: Dhiraj Brahman, Biswajit Sinha
    Abstract:

    Abstract Partial molar volumes ( ϕ V 0 ) and viscosity B-coefficients of salicylaldehyde anil zinc (II), abbreviated as SAZ, in (0.00, 0.02, 0.04 and 0.05) mol ⋅ dm−3 Tetrabutylammonium Bromide (Bu4NBr) solutions in methanol (MeOH) were determined from solution density and viscosity measurements at (298.15, 308.15 and 318.15) K under ambient pressure. Apparent molar volumes (ϕV) and solution densities (ρ) were further used to determine isobaric apparent molar expansibilities (ϕE), isobaric partial molar expansibilities ( ϕ E 0 ) and temperature dependence of isobaric partial molar expansibilities ( ϕ E 0 ) at constant pressure, ( ∂ ϕ E 0 / ∂ T ) P of SAZ solutions to study the nature of different interactions in the ternary solutions. The transition state theory was applied to analyze the viscosity B-coefficients of the ternary solutions on the basis of the activation parameters of viscous flow. The overall results indicated strong solute–solvent interactions between SAZ and the solvent mixture and SAZ acts as a net structure breaker in the ternary solutions. UV-Visible absorption spectra of the ternary solutions also stand in support of the results obtained.

  • apparent molar volumes and viscosity b coefficients of nicotinamide in aqueous Tetrabutylammonium Bromide solutions at t 298 15 308 15 and 318 15 k
    The Journal of Chemical Thermodynamics, 2008
    Co-Authors: Biswajit Sinha, Bipul Kumar Sarkar, Mahendra Nath Roy
    Abstract:

    Abstract Apparent molar volumes ϕV and viscosity B-coefficients for nicotinamide in (0.00, 0.05, 0.10, and 0.15) mol · dm−3 aqueous Tetrabutylammonium Bromide (TBAB) solutions have been determined from solution density and viscosity measurements at temperatures over the range (298.15 to 318.15) K as function of concentration of nicotinamide (NA). In the investigated temperature range, the relation: ϕ V ∘ = a 0 + a 1 T + a 2 T 2 , have been used to describe the temperature dependence of the standard partial molar volumes ϕ V ∘ . These results have, in conjunction with the results obtained in pure water, been used to deduce the standard volumes of transfer Δ ϕ V ∘ and viscosity B-coefficients of transfer for nicotinamide from water to aqueous TBAB solutions for rationalizing various interactions in the ternary solutions. The structure making or breaking ability of nicotinamide has been discussed in terms of the sign of ( δ 2 ϕ V ∘ / δ T 2 ) P . An increase in the transfer volume of nicotinamide with increasing TBAB concentration has been explained by Friedman–Krishnan co-sphere model. The activation parameters of viscous flow for the ternary solutions investigated were also determined and discussed by the application of transition state theory.

Ramesh C. Sharma - One of the best experts on this subject based on the ideXlab platform.

  • conductance studies of Tetrabutylammonium Bromide sodium Bromide and sodium tetraphenylborate in 2 butoxyethanol 1 water 2 mixtures at 298 15 303 15 308 15 and 313 15 k
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Binod Sharma, Ramesh C. Sharma
    Abstract:

    Electrical conductances of solutions of Tetrabutylammonium Bromide (Bu4NBr), sodium Bromide (NaBr), and sodium tetraphenylborate (NaBPh4) in 2-butoxyethanol (1) + water (2) mixture with 0.017, 0.037, 0.061, 0.092, and 0.132 mole fraction of 2-butoxyethanol have been reported at (298.15, 303.15, 308.15, and 313.15) K. The experimental values of electrical conductances are analyzed using the 1978 Fuoss conductance–concentration equation to obtain the values of limiting molar conductance (Λ0), ionic association constant (KA), and the association diameter (R). The values of KA and R obtained for these three salts, namely, Tetrabutylammonium Bromide, sodium Bromide, and sodium tetraphenylborate, suggests a weak electrostatic ion–solvent interaction and that they exist as free ions in all the solvent compositions and the temperature range covered in this study. The Walden products of these salts deviate from ideal behavior with varying temperature and solvent composition.

Amritendu Chatterjee - One of the best experts on this subject based on the ideXlab platform.

  • electrical conductances of Tetrabutylammonium Bromide sodium tetraphenylborate and sodium Bromide in ethylene glycol 1 water 2 mixtures at 298 15 303 15 308 15 and 318 15 k
    Journal of Chemical & Engineering Data, 2004
    Co-Authors: Ramesh Sharma, Chanchal Das, Amritendu Chatterjee
    Abstract:

    The electrical conductances of the solutions of Tetrabutylammonium Bromide (Bu4NBr), sodium tetraphenylborate (NaBPh4), and sodium Bromide (NaBr) in methanol (1) + water (2) mixed solvent media containing 0.10, 0.20, and 0.30 volume fractions of methanol have been reported at (298.15, 308.15, and 318.15) K. The conductance data have been analyzed by the 1978 Fuoss conductance−concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA), and the association diameter (R). The ionic contributions to the limiting molar conductance have been estimated using Tetrabutylammonium tetraphenylborate (Bu4NBPh4) as the “reference electrolyte”. All of these three electrolytes are found to exist as free ions in the present solvent mixtures within the temperature range (298.15 to 318.15) K. Besides the relative permittivity and the viscosity of the media, specific interactions of the ions with the solvent media have been found to play a profound influence on their mobilities. Alth...