Vapor pressure data for non-aqueous electrolyte solutions. Part 5. Tetraalkylammonium salts in acetonitrile

Precise vapor pressure data for solutions of Et₄NBr (concentration range of 0.04–1]<0.4), Pr₄NBr (0.044NBr (0.024NCl (0.044NI (0.054NBr (0.06相似文献   

Vapor pressure measurements on non-aqueous electrolyte solutions. Part 2. Tetraalkylammonium salts in methanol. Activity coefficients of various 1-1 electrolytes at high concentrations

Precise vapor pressure data for solutions of Et₄NBr, Bu₄NBr, Bu₄Nl, Bu₄NClO₄, and Am₄NBr in methanol at 25°C in the concentration range 0.04–1]<1.6 are communicated and discussed. Polynomials in molalities are given which may be used for calculating precise vapor pressure depressions of these solutions. Osmotic coefficients are calculated by taking into account the second virial coefficient of methanol vapor. Discussion of the data at low concentrations is based on the chemical model of electrolyte solutions taking into account non-coulombic interactions; ion-pair association constants are compared to those of conductance measurements. Pitzer equations are used to reproduce osmotic and activity coefficients at high concentrations; the set of Pitzer parameters b=3.2, ₁ = 2.0, and ₂ = 20.0 is proposed for methanol solutions.     

Viscosities and densities of tetraalkylammonium bromides in dimethylformamide-water mixtures at 25 and 35°C

Viscosity and desity data for KCl, KBr, Me₄NBr, Et₄NBr, Pr₄NBr, and Bu₄NBr from 0.005 to 3M in aqueous dimethylformamide solutions at 25°C and 35°C are presented. The data for dilute solutions were analyzed by means of the Jones-Dole equation and the ionic B coefficients evaluated. The data for concentrated solutions were analyzed by the Breslau and Miller equation and the effective flow volume, V₃ of the electrolytes obtained as a function of concentration. The limiting effective flow volume, V _e ^o was obtained from the Vand equation in the form used by Eagland and Pilling and it is shown that B=2.5 V _e ^o . With increasing DMF concentration V _e ^o increases for Me₄NBr but decreases for Pr₄NBr and Bu₄NBr. The same effect was observed by increasing temperature. This behavior is explained in terms of the structuring effect of the constituent ions and the effect of DMF on the overall structure of the binary solvent.     

Osmotic and activity coefficients at 25°C for tetraalkylammonium bromides in deuterium oxide

Earlier work by Lindenbaum and Boyd has demonstrated the important role of hydrophobic interactions involving the water solvent in determining the osmotic coefficients and properties of aqueous solutions of the tetraalkylammonium halides. Osmotic coefficients of solutions of tetramethyl-, tetraethyl-, tetrapropyl-, and tetrabutylammonium bromides in the more highly structured solvent D₂O have now been determined by the gravimetric isopiestic method, using reference solutions of NaCl in D₂O. The data were fitted to the Rush-Johnson and Pitzer equations. Satisfactory agreement with the results for aqueous solutions at comparable concentrations indicates that the solution chemistry of these quaternary ammonium bromides is not highly dependent on the degree of structure of the pure solvents. Supplementary data for mixtures of Me₄NBr with Et₄NBr, Pr₄NBr, or Bu₄NBr in both H₂O and D₂O are consistent with this conclusion.On leave 1980–82 from Banaras Hindu University, India     

Viscosities of Some Tetraalkylammonium and Alkali-Metal Salts in N,N-Dimethylacetamide at 25°C

The viscosities of solutions of tetrapropylammonium bromide (Pr₄NBr), tetrabutylammonium bromide (Bu₄NBr), tetrapentylammonium bromide (Pen₄NBr), tetrahexylammonium bromide (Hex₄NBr), tetraheptylammonium bromide (Hep₄NBr), tetraoctylammonium bromide (Oct₄NBr), tetrabutylammonium tetraphenylborate (Bu₄NBPh₄), sodium tetraphenylborate (NaBPh₄), and potassium tetraphenylborate (KBPh₄) in N,N-dimethylacetamide are reported at 25^°C. The viscosity data havebeen analyzed by the Jones-Dole equation for associated electrolytes to evaluate the viscosity B coefficients of the electrolytes. These data have also been analyzed by the transition-state theory to obtain the contribution of the solutes to the free energy of activation for viscous flow of the solution. The ionic contribution to the viscosity B coefficient and the free energy of activation for viscous flow have been estimated using of the reference electrolyte Bu₄NBPh₄. The bromide, tetraphenylborate, and tetraalkylammonium ions are found to be weakly solvated in N,N-dimethylacetamide, whereas significant solvation has been detected for sodium and potassium ions. The viscosity of the solvent is greatly modified by the presence of all the ions investigated here with the exception of the bromide ion.     

Thermal properties of <Emphasis Type="Italic">n</Emphasis>-R<Subscript>4</Subscript>NBr solutions in binary solvents containing formamide

The enthalpies of solution of tetraethyl- and tetra-n-hexylammonium bromides have been measured in mixtures of formamide with ethylene glycol at 298.15 and 313.15 K in the whole mole fraction range by the calorimetric method. The standard enthalpies of solution in binary mixtures have been calculated with Redlich–Rosenfeld–Meyer type equation. The enthalpy and heat capacity parameters of pair interaction of organic electrolytes with EG in FA and with FA in EG have been computed and discussed. The enthalpy interaction parameters of single ions with EG in FA medium have been evaluated and compared with those for ion–water and ion–MeOH interaction in FA. The standard heat capacities of solution have been evaluated. The excess enthalpies of solution, Δ_sol H ^E, of Et₄NBr, Bu₄NBr, and Hex₄NBr have been determined. The Δ_sol H ^E values are positive for Et₄NBr and negative for Bu₄NBr and Hex₄NBr and become more negative from Bu₄NBr to Hex₄NBr.     

Transport behavior in isomeric alcohols. I. The conductance of tetraalkylammonium salts in isobutyl and isopentyl alcohols at 25°C

Conductance measurements at 25°C have been carried out on Pr₄NBr, Bu₄NBr,n-Pe₄NPr, Pr₄NI, Bu₄NI,n-Pe₄NI, Bu₄NClO₄, Bu₄NBF₄, and Bu₄PClO₄ in isobutyl alcohol and on Bu₄NBr and Bu₄NClO₄ in isopentyl alcohol. The main purpose of the measurements was to investigate the effect of increased branching in the alkyl portion of the alcohol on both ionic mobilities and ionic association. Comparison is made with the two isodielectric solvents butanone andn-butyl alcohol. Branching appears to produce little change in ionic mobilities and approximately a 10% increase in association.     

Thermal properties of tetraalkylammonium bromides in several solvents

The enthalpies of solution of tetraethyl- and tetra-n-hexylammonium bromides have been measured in mixtures of formamide with ethylene glycol at 298.15 and 313.15 K in the whole mole fraction range by the calorimetric method. The standard enthalpies of solution in binary mixtures have been calculated with Redlich–Rosenfeld–Meyer type equation. The enthalpy and heat capacity parameters of pair interaction of organic electrolytes with EG in FA and with FA in EG have been computed and discussed. The enthalpy interaction parameters of single ions with EG in FA medium have been evaluated and compared with those for ion–water and ion–MeOH interaction in FA. The standard heat capacities of solution have been evaluated. The excess enthalpies of solution, Δ_sol H ^E, of Et₄NBr, Bu₄NBr, and Hex₄NBr have been determined. The Δ_sol H ^E values are positive for Et₄NBr and negative for Bu₄NBr and Hex₄NBr and become more negative from Bu₄NBr to Hex₄NBr.     

Influences of Micelle Formation and Added Salts on the Hydrolysis Reaction Rate of p‐Nitrophenyl Benzoate in Aqueous Buffered Media

The hydrolysis reaction rate of p‐nitrophenyl benzoate (p‐NPB) has been examined in aqueous buffer media of pH 9.18, containing surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), or sodium dodecyl sulfate (SDS) at 35°C. Although the rate constant [log (k /s⁻¹)] of p‐NPB hydrolysis has once decreased slightly below the critical micelle concentration (CMC) value for CTAB and CTAC, it has begun to increase drastically with micellar formation. With increasing concentrations larger than the CMC value, the log (k /s⁻¹) value has reached the optimal value, i.e., a 140‐ and 200‐fold rate acceleration for CTAB and CTAC, respectively, compared to that without a surfactant. Whereas the anionic surfactant, SDS, has caused only a gradual rate deceleration in the whole concentration range (up to 0.03 mol dm⁻³). Increases in pH of the buffer have resulted in increases of the hydrolysis rate. In the CTAB micellar solution, the remarkably enhanced rate has been retarded significantly by the addition of only 0.10 mol dm⁻³ bromide salts. The effects of rate retardation caused by the added salts follows in the order of NaBr > Me₄NBr > Et₄NBr > Pr₄NBr > n‐Bu₄NBr. In the absence of surfactant, however, the addition of the bromide salts has accelerated the hydrolysis rate, except for the metallic salt of NaBr, with the order of Me₄NBr < Et₄NBr < Pr₄NBr < n‐Bu₄NBr. In the CTAC micellar solution, similar rate retardation effects have been observed in the presence of chloride salts (NaCl, Et₄NCl, and n‐Bu₄NCl). The effects of added salts have been interpreted from the viewpoints of the changes in activity of the OH⁻ ion and/or the nucleophilicities of the anions from the added salts.     

Thermodynamic characteristics of solvation of individual ions in ethanol at −50 to 55°C

Experimentally determined are the enthalpies of solution of 12 electrolytes (LiBr, LiI, NaBr, NaI, NaBPh₄, Et₄NCl, Et₄NBr, Pr₄Br, Bu₄NBr, Am₄NBr, Ph₄PCl, Ph₄PBr) in ethanol at –50 to 55°C. _sH^o values obtained on the basis of four different extrapolation equations are analyzed. The effect of temperature changes on the thermodynamic parameters of solvation indindividual ions are calculated using thermodynamic data for the salt crystals (lattice) with the assumption that _solvC _p ^o (Ph₄P⁺)=_solvC _p ^o (Ph₄P^-).     

Isopiestic determination of the osmotic and activity coefficients of dilute aqueous solutions of symmetrical and unsymmetrical quaternary ammonium bromides with a new isopiestic cell at 298.15 K

The osmotic coefficients of Bu₄NBr, sec-Bu₄NBr, iso-Bu₄NBr, Bu₂Et₂NBr and Bu₃EtNBr were determined by isopiestic method at 298.15 K in dilute aqueous solutions. A branched isopiestic cell was used. The osmotic coefficients of tetra-alkyl-ammonium solutions were analyzed comparing these with the Debye–Hückel limiting law. The order of the osmotic coefficient variation is Bu²Et₂N⁺ > BuEt₃N⁺ > sec-Bu₄N⁺ > iso-Bu₄N⁺ > n-Bu₄N⁺. The results were fitted to the Pitzer equation and the parameters β₀ and β₁ were calculated. The results are discussed.     

Enthalpies of Transfer of Tetraalkylammonium Bromides and CsBr from water to Aqueous DMF at 298.15 K

Enthalpies of transfer of tetraalkylammonium bromides and CsBr from water to aqueous DMF mixtures are reported and analyzed in terms of a new solvation theory. It was found that a previous equation could not reproduce these data over the whole range of solvent compositions. Using a new solvation theory to model the enthalpies of transfer shows excellent agreement between experimental and calculated values over the entire range of solvent compositions. The analyses show that tetrapropylammonium bromide, Pr₄NBr, and tetrapentylammonium bromide, Pen₄NBr, are preferentially solvated by water; in contrast tetrabutylammonium bromide, Bu₄NBr, is preferentially solvated by DMF. The solvation of tetramethylammonium bromide, Me₄NBr, and cesium bromide, CsBr, is random. The extent to which the tetraalkylammonium bromides disrupt solvent–solvent bonds increases systematically in going from Me₄NBr to Pen₄NBr.     

Apparent molal volumes and heat capacities of some 1:1 electrolytes in anhydrous methanol at 25°C

A flow calorimeter and flow densimeter have been used to measure volume specific heats and densities of solutions of LiCl, LiBr, NaCl, NaBr, KF, KBr, Kl, CsF, and Bu₄NBr in anhydrous methanol at 25°C. The concentrations ranged from approximately 0.01m to close to saturation in some cases. Apparent molal heat capacities _cp and volumes _v have been evaluated and extrapolated to infinite dilution to obtain _cp ^o and _v ^o . Nearly all the heat capacities in methanol are negative. However, with the exception of the lithium halides and Bu₄NBr they are more positive than heat capacities of the corresponding salts in water. The dependence of the heat capacities on ionic radii is generally opposite in methanol solutions from that observed for aqueous solutions. In agreement with others, the _v ^o data indicate that electrostriction in methanol solutions is greater than in aqueous solutions.     

Electrophilic Bromination of N‐Acylated Cyclohex‐3‐en‐1‐amines: Synthesis of 7‐Azanorbornanes

The intramolecular bromo‐amidation and the dibromination‐cyclisation of the N‐acylcyclohex‐3‐en‐1‐amines 4, 8, 9, 11, 13, 14 , and 16 was studied in view of the synthesis of bicyclic amines that are of interest as building blocks and potential glycosidase inhibitors. The trifluoroacetamides 4, 9 , and 14 reacted with N‐bromosuccinimide (NBS) in AcOH to give dihydro‐1,3‐oxazines in good yields. The stereoselectivity of the dibromination of the alkenes 8 and 9 depends on the nature of the protecting group, the reagent, and the reaction conditions. Br₂ in CH₂Cl₂ transformed the alkenes 8 and 9 predominantly into diaxial trans,trans‐dibromides. Bromination of 9 with PhMe₃NBr₃ or with Br₂ in the presence of Et₄NBr gave predominantly the diequatorial trans,cis‐ 27 besides some trans,trans‐ 28 . A similar bromination of the C(5)‐substituted N‐acyl‐4‐aminocyclohexenes 11, 13, 14 , and 16 with PhMe₃NBr₃ was accompanied by intramolecular side reactions that were suppressed by the addition of excess Et₄NBr. Under these conditions, 11 gave diastereoselectively trans‐dibromides, while its reaction with Br₂ gave trans‐dibromides along with the dihydrooxazinone 31 . Also the carbamate 13 reacted with PhMe₃NBr₃/Et₄NBr selectively to the trans‐dibromide 32 and with Br₂ to the trans‐dibromides 32 and 33 , the dihydrooxazinone 34 , and the bicyclic ether 35 . Similarly, the trifluoroacetamide 14 provided the dibromide 36 (89%), while its reaction with Br₂ led to the dihydrooxazine 22 , and the dibromides 36 and 37 . The N‐benzyl‐N‐Boc derivative 16 did not yield any dibromide; it reacted with PhMe₃NBr₃/Et₄NBr to the dihydrooxazinone 38 , and with Br₂ to the oxazinone 38 and the bicyclic ether 39 . The high stereoselectivity of the bromination with PhMe₃NBr₃/Et₄NBr suggests an anchimeric assistance of the NHR substituent. Deprotection, cyclisation, and carbamoylation transformed the dibromides 27, 29 , and 32 into the 7‐azanorbornanes 42, 49 , and 53 . The diols 45 and 57 were obtained from 42 and 53 via HBr elimination and stereoselective dihydroxylation; they proved weak inhibitors of several glycosidases. In no case could the formation of a bicyclic azetidine (6‐azabicyclo[3.1.1]heptane) from the dibromides 26 and 30 be observed.     

Photoinduced Metal-Free Decarboxylative Transformations: Rapid Access to Amines,Alkyl Halides,and Olefins

Herein, we report an efficient photocatalytic strategy for the decarboxylative transformations of redox-active esters to construct C=C, C(sp³)−N, and C(sp³)−X bonds in a single-step. This operationally simple method provides a straightforward access to a variety of protected alkyl amines, alkyl halides and olefins under mild conditions in the absence of metals and photocatalysts. The method can successfully be applied to primary, secondary, and tertiary aliphatic carboxylic acid derivatives. Mechanistic studies indicate that the charge transfer complex (CTC) was formed by ⁿBu₄NI with redox-active esters, in which the ⁿBu₄NI acted as both an iodine source and an efficient electron donor.     

Heat properties of Bu<Subscript>4</Subscript>NBr solutions in binary mixtures based on formamide

Heat effects of tetrabutylammonium bromide dissolution in mixtures of formamide with methanol and ethylene glycol at 25°C were determined. Partial molar enthalpies of the components of formamide-ethylene glycol mixtures at 25°C were measured by the calorimetric method, and the mixing enthalpies of this system were determined. Within the limits of the second approximation of the Debye-Hueckel theory the standard enthalpies of dissolution Δ_dis H ⁰ were calculated, and the enthalpies of Bu₄NBr transfer from formamide in its mixtures with water methanol and ethylene glycol were found on this basis. The enthalpy parameters of Bu₄NBr pair interactions with the components of the formamide-water, formamide-methanol, and formamide-ethylene glycol mixtures were calculated. The results obtained were compared with the data for the systems containing N-methylformamide and N,N-dimethylformamide.     

Ion association and ultrasonic relaxation in hydrogen-bonding solvents: 1:1 Electrolytes in 2-propanol at 25°C

Ultrasonic absorption measurements have been carried out in aqueous solutions of Bu₄NCl, Bu₄NBr, Bu₄NI, Me₄NCl, and LiCl in 2-propanol over the frequency range 15–250 MHz. A single relaxation frequency was observed for each system. All the data were found to be consistent with a 2-step association mechanism in which the rate-determining step was the diffusion of the ions to form a solventseparated ion pair, followed by rapid desolvation to form the contact ion pair. Measured association rate constants were very nearly those predicted for a diffusion-controlled process.     

Effects of H/D-isotope substitution and temperature on the volume characteristics of tetra-n-butylammonium bromide dissolved in methanol and its D-isotopomers

Densities of Buⁿ ₄NBr solutions in MeOH, MeOD, and CD₃OH were measured at salt concentrations of up to 1.5 solvomolality units (nearly 2.63·10^–2 mole fraction) at 278.15, 288.15, 298.15, 308.15, and 318.15 K. The limiting partial molar volumes of Buⁿ ₄NBr dissolved in these alcohols were calculated. The isotope effects in the volume characteristics of the stoichiometric mixture of ions, [Buⁿ ₄N⁺ + Br^–], are mainly due to the vibrational changes in the solvent structure upon deuteration of different molecular fragments. Structural transformations in infinitely dilute solution of Buⁿ ₄NBr in methanol are governed by non-specific solvation of the symmetrical Buⁿ ₄N⁺ cation.     

Conductance of electrolytes in 1-propanol solutions from −40 to 25°C

Conductance data for solutions of LiCl, NaBr, NaI, KI, KSCN, RbI, Et₄NI, Pr₄NI, Bu₄NI, Bu₄NClO₄, n-Am₄NI, i-Am₄NI, n-Hept₄NI, Me₂Bu₂NI, MeBu₃NI, EtBu₃NI, i-Am₃BuNI, and i-Am₃BuNBPh₄ in 1-propanol at –40, –30, –20, –10, 0, 10, and 25°C are communicated and discussed. Evaluation of the data is performed on the basis of a conductance equation that includes a term in c^3/2. Single ion conductances at 25 and 10°C are determined with the help of transference numbers t _o ⁺ (KSCN/PrOH); the data are compared to data estimated by other methods. Ion-pair association constants and their temperature dependence are discussed in terms of contact and solvent separated ion pairs, and the role of non-coulombic forces is shown with the help of an appropriate splitting of the Gibbs energy of ion-pair formation.     

The conductance of tetrabutylammonium salts in water-sulfolane mixtures at 30°C

Conductance measurements are reported for Bu ₄ NCl, Bu ₄ NBr, Bu ₄ NI, and Bu ₄ NClO ₄ at 30°C in water-sulfolane mixtures over the entire solvent composition range. Experimental data were analyzed by the 1965 Fuoss-Onsager-Skinner equation. The limiting equivalent conductances in water and in sulfolane were compared with literature values. The trends of the Walden products are discussed in terms of water structural changes caused by addition of sulfolane. As expected, on the basis of previous results reported in the literature, a significant amount of association was detected for Bu ₄ NI in water. Very small association constants were also found for Bu ₄ NI and Bu ₄ NClO ₄ at 10 wt.% sulfolane.