Uncharged Co(lll) Complexes: Transfer Chemical Potentials and Base Hydrolysis in Water-Methanol Mixtures

Solubilities are reported for three Co(III) complexes of 2-aminophenol, 2-amino-4-nitrophenol and 6-amino-2,4-dimethylphenol. Transfer chemical potentials have been derived from appropriate solubility measurements in aqueous methanol. The trends in transfer chemical potentials are discussed in terms of the nature of the coordinated ligands and are compared with those for selected of other inorganic Co(III) complex ions. The kinetics of base hydrolysis of Co(III) complexes in aqueous methanol solutions are described and the change in the activation barrier δ_mΔG^≠ is determined. Solvent effects on reactivity trends are analysed into initial state and transition state components. The small decrease in the rate constant, with increasing proportion of methanol, is ascribed to a greater effect of solvent on the initial state.     

Separation of Sulphonium Salts by Ion Chromatography: Five- and Six-Membered Cyclic Sulphonium Salts

Abstract

Several cyclic 5-and 6-membered sulphonium compounds were separated by ion pair chromatography on a opti-dbb ion pair column. The salts show specific retention behavior when using different mixtures of acetonitrile and aqueous sodium perchlorate solutions as eluents. The increase of retention times with extending chain length of the alkyl group R and with ring size is due to an increase of the solute molecular surface areas which were also calculated. The obtained retention parameters give additional information for structural determination.     

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.     

Volumetric, viscometric and refractive index behavior of some α-amino acids in aqueous tetrapropylammonium bromide at different temperatures

Densities, ρ, viscosities, η, and refractive indices, n _D, of glycine (Gly), DL-alanine (Ala), DL-valine (Val) (0.05, 0.10, 0.15, 0.20, 0.25 mol kg^?1), and L-leucine (Leu) (0.02, 0.05, 0.10 mol kg^?1) in water and in 0.20 mol kg^?1 aqueous tetrapropylammonium bromide (TPAB) have been measured at 298.15, 303.15, 308.15, and 313.15 K. The density data have been utilized to calculate apparent molar volumes, ?_v, partial molar volumes at infinite dilution, ?_v°, and partial molar volumes of transfer, ? _v°(tr) of amino acids. The viscosity data have been analyzed by means of Jones-Dole equation to obtain Falkenhagen coefficient, A, and Jones-Dole coefficient, B, free energy of activation of viscous flow per mole of solvent, Δµ₁°*, and solute, Δµ₂°*, and enthalpy, ΔH*, and entropy of activation, ΔS*, of viscous flow. The refractive index data have been used to calculate molar refractivity, R _D, of amino acids in aqueous tetrapropylammonium bromide solutions. It has been observed that ?_v°, B-coefficient and Δµ₂°* vary linearly with increasing number of carbon atoms in the alkyl chain of amino acids, and they were split to get contributions from the zwitterionic end groups (NH₃ ⁺, COO^-) and methylene group (CH₂) of the amino acids. The behavior of these parameters has been used to investigate the solute-solute and solute-solvent interactions as well as the effect of tetrapropylammonium cation (C₃H₇)₄N⁺ on these interactions.     

Optimization of Chlorophyllase-catalyzed Hydrolysis of Chlorophyll in Monophasic Organic Solvent Media

The effects of selected reaction parameters, including solvent hydrophobicity, initial water activity, agitation speed, temperature and enzyme concentration, on the biocatalytic efficiency of a chlorophyllase enzymatic extract from Phaeodactylum tricornutum in neat organic solvent media were investigated. The highest chlorophyllase specific activity of 322 nmol hydrolyzed chlorophyll per gram of protein per minute and bioconversion yield of 91% were obtained in the reaction mixture of hexane/2-octanone (98.3:1.7, v/v), at a controlled initial water activity of 0.90. R _O/A value, which is the ratio of the specific activity in the organic solvent to that in the aqueous/miscible organic solvent medium, was 1.5 × 10⁻³. To reduce the substrate diffusional limitations, the appropriate agitation speed and enzyme concentration were determined. The optimum temperature for maximal enzymatic activity and activation energy were 35°C and 105.0 kJ/mol, respectively. Although the catalytic efficiency of chlorphyllase in the neat organic solvent mixture was lower than that in the aqueous medium, its half-life time in the first environment at temperature ranging from 35 to 50°C was increased by 5.0 to 15.0 times.     

Acidic Peroxo Salts: A New Class of Initiators for Vinyl Polymerization. IV. Kinetics of Polymerization of Methyl Methacrylate Initiated by Potassium Monopersulfate Catalyzed by Ag(l)

Abstract

Kinetics of vinyl polymerization of methyl methacrylate (MMA) initiated by an acidic peroxo salt, such as potassium monopersulfate coupled with silver nitrate, have been investigated in aqueous medium over the temperature range from 35 to 50°C. The rates of polymerization (R_p) have been computed for various concentrations of the monomer and initiator. The effectiveness of various metal salts in catalyzing the polymerization reaction has been determined from the observed R_p values. The effects of the catalyst (AgNO₃), initiator, monomer, and various secondary aliphatic and aromatic amines on R_p and percentage conversion have been studied. The endgroups of the resultant polymers have been studied using standard methods. From the observed endgroups and kinetic results, a reaction scheme has been proposed involving initiation by ′OH or SO₄ ^? radicals, generated by the interaction of the initiator with silver nitrate and termination by mutual combination.     

Two-Step Electrodialysis Treatment of Monoethanolamine to Remove Heat Stable Salts

Electrodialysis technology was adapted to removal of heat stable salts from aqueous solutions of alkanolamine absorbents, with monoethanolamine as example. Removal of anions of heat stable salts by electrodialysis from a 30 wt % aqueous solution of monoethanolamine with the degree of carbonation of 0.2 mol of CO₂ per mole of monoethanolamine was studied. The two-step removal of heat stable salts by electrodialysis allows the monoethanolamine loss to be reduced and the concentration of residual CO₂ in the absorbent solution to be decreased. The suggested two-step electrodialysis treatment scheme allows the concentration of heat stable salts to be maintained on the required level from the viewpoint of their corrosion activity, the total volume of the concentrate to be decreased by 50%, and the monoethanolamine loss to be decreased by 30%. The treatment unit with the circulation volume of the monoethanol absorbent of 100 m³ h^–1 was calculated for confirming the efficiency of the two-step electrodialysis treatment scheme. As compared to the one-step electrodialysis treatment scheme, the two-step scheme ensures recovery of 50% of monoethanolamine at the same efficiency of the removal of heat stable salts.     

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.     

Steric and Inductive Effects on Ionic Association in Aqueous Solutions Using an ion Selective Electrode Technique. II. Magnesium Salts

The stoichiometric association constants, K, the thermodynamic association constants, K_A, and the thermodynamic parameters ΔS°, ΔH°, ΔG° for the association between Mg(II) ion with o-, m and p-toluates,o-,m, and p-chlorobenzoates, and o-, m- and p-bromobenzoates have been determined at 15°C, 25°C, 35°C and 45°C in aqueous media. Ion selective electrodes were used to measure the Mg^{2 +} activities. The trends in the association behavior of Mg(II) salts of aromatic acids connot be explained on the basis of steric effects but can be explained according to the trend of the pKa of the parent organic acids, and the Hammett function, σ, of the salts themselves relative to the corresponding benzoate salt.     

Behaviour of Salbutamol on Diol Normal-Phase Column

Summary The behaviour of salbutamol, a sympathomimetic amine-and catecholamine-like substance, was studied on Diol normal-phase column. The possibility for controlled retention of salbutamol using methanol containing mobile phase was proved. The mobile phase consisted of buffer (0.05 M H₃PO₄, pH 5.0 with TEA) – methanol (15:85 v/v). The effects of organic solvent, pH, ion power of the buffer and the length of amine alkyl chain in buffer were studied. The retention of salbutamol increased significantly with the increase of methanol content above 80%. At pH values between 3.5 and 7.5 the retention of salbutamol varied from 2.16 to 2.36 only. The limit of quantitation was 0.30 ng · mL^–1. The investigations confirm the H-bonding retention mechanism.     

Solution studies of tris(2-benzylaminoethyl)amine complexes of zinc(II) and copper(II): The catalytic hydrolysis of toxic organophosphate

Solution studies of the tetradentate ligand tris(2-benzylaminoethyl)amine, BzTren with both zinc(II) and copper(II) salts were investigated in aqueous methanol (33% v/v) by means of ¹H NMR, potentiometric, and UV-visible titrations as well as cyclic voltammetry. Subsequently, their zinc(II) and copper(II) complexes [BzTren-M(OH₂)]²⁺ 1 and 2 (M²⁺ = Zn²⁺ and Cu²⁺) were synthesized and fully characterized by using FT-IR spectroscopy, elemental analysis, and thermal analysis. Complexes 1 and 2 are investigated kinetically for the catalytic hydrolysis of the toxic organophosphate parathion at 50 °C in aqueous methanol (33%, v/v). The kinetic results indicate that copper(II) complex 2 is more active than zinc(II) complex 1, presumably a reflection of the effective electron-withdrawing as well as the greatest electrophilicity of copper(II) ion.     

Effects of concentration and temperature on molar volumes of L-serine, L-isoleucine, and L-glutamine in aqueous NaCl and NaNO3 solutions

Densities of L-serine, L-isoleucine, L-glutamine in 1.5 mol kg^?1 aqueous NaCl, and NaNO₃ solutions have been measured for several molal concentrations of amino acids at temperatures from 298.15 to 323.15 K. The partial molar volumes (? _v ⁰ ) of L-serine, L-isoleucine, and L-glutamine in 1.5 mol kg^?1 aqueous NaCl/NaNO₃ solutions have been computed using density data. The transfer partial molar volumes (Δ_tr? _v ⁰ ) of L-serine, L-isoleucine, and L-glutamine from water to 1.5 mol kg^?1 aqueous NaCl/1.5 mol kg^?1 aqueous NaNO₃ solutions have been determined at 298.15 K. The trends of variation of ? _v ⁰ and Δ_tr? _v ⁰ with change in temperature have been discussed in terms of ion-ion, ion-hydrophilic, and ion-hydrophobic interactions operative in solutions.     

The Effect of β‐Hydrogen Atoms on Iron Speciation in Cross‐Couplings with Simple Iron Salts and Alkyl Grignard Reagents

The effects of β‐hydrogen‐containing alkyl Grignard reagents in simple ferric salt cross‐couplings have been elucidated. The reaction of FeCl₃ with EtMgBr in THF leads to the formation of the cluster species [Fe₈Et₁₂]^2?, a rare example of a structurally characterized metal complex with bridging ethyl ligands. Analogous reactions in the presence of NMP, a key additive for effective cross‐coupling with simple ferric salts and β‐hydrogen‐containing alkyl nucleophiles, result in the formation of [FeEt₃]^?. Reactivity studies demonstrate the effectiveness of [FeEt₃]^? in rapidly and selectively forming the cross‐coupled product upon reaction with electrophiles. The identification of iron‐ate species with EtMgBr analogous to those previously observed with MeMgBr is a critical insight, indicating that analogous iron species can be operative in catalysis for these two classes of alkyl nucleophiles.     

Asymmetric oxidation of sulfides catalyzed by (R)-6,6'-dibromo-BINOL derived titanium complex

Abstract

An efficient asymmetric oxidation of sulfides was achieved using (R)-6,6'-dibromo-BINOL as chiral ligand in combination with Ti(OⁱPr)₄ using 70% aqueous tertiary butyl hydroperoxide as oxidant. The resulting sulfoxides had high enantiopurities and good yields. A range of aryl alkyl and aryl benzyl sulfides were oxidized to the corresponding sulfoxides with 78–95% ee in 72–80% yields.     

A CONVENIENT SYNTHESIS OF ALKYLPHOSPHONIUM SALTS

Abstract

The reaction of methanol and its homologs with Ph₃ P in 48% aqueous hydrobromic acid provides alkyltriphenylphosphonium salts in quantitative yields.     

Thermodynamics of bolaform electrolytes. IV. Enthalpies and partial molal heat capacities in H2O,D2O,and dimethylsulfoxide

The partial molal heats of solution ΔH _s ^o and the partial molal heat capacities of solution ΔC _p ^o of the bolaform salts [Et₃N(CH₂)_nNEt₃]Br₂ and [allyl₃N(CH₂)_nNallyl₃]Br₂ have been obtained at infinite dilution in dimethylsulfoxide (DMSO). A comparison of these data with the results of previous thermodynamic studies of the same solutes in aqueous solvents has been carried out. The observed differences have been interpreted in terms of solute-induced solvent structural effects occurring in aqueous solvent media. Partial molal heat capacities of the bolaform salts at infinite dilution in DMSO, H₂O, and D₂O have been calculated from ΔC _p ^o data and previously reported values of the heat capacities of the crystalline state. The data clearly show that the structure-promoting capabilities of these salts in aqueous solvents increase with increasing hydrocarbon content. A comparison of contributions to partial molal heat capacities of methylene groups in the bolaform and R₄N⁺ series of salts reveals that similarities exist between the solvation effects of CH₂ groups in the normal alkyl chain of the R₄N⁺ cations and in the bridging alkyl chain of the bolaform cation.     

Revealing the Interfacial Chemistry of Fluoride Alkyl Magnesium Salts in Magnesium Metal Batteries

Exploring promising electrolyte-system with high reversible Mg plating/stripping and excellent stability is essential for rechargeable magnesium batteries (RMBs). Fluoride alkyl magnesium salts (Mg(OR^F)₂) not only possess high solubility in ether solvents but also compatible with Mg metal anode, thus holding a vast application prospect. Herein, a series of diverse Mg(OR^F)₂ were synthesized, among them, perfluoro-tert-butanol magnesium (Mg(PFTB)₂)/AlCl₃/MgCl₂ based electrolyte demonstrates highest oxidation stability, and promotes the in situ formation of robust solid electrolyte interface. Consequently, the fabricated symmetric cell sustains a long-term cycling over 2000 h, and the asymmetric cell exhibits a stable Coulombic efficiency of 99.5 % over 3000 cycles. Furthermore, the Mg||Mo₆S₈ full cell maintains a stable cycling over 500 cycles. This work presents guidance for understanding structure–property relationships and electrolyte applications of fluoride alkyl magnesium salts.     

The Effect of Moisture on the Hydrolysis of Basic Salts

A great deal of information exists concerning the hydration of ions in bulk water. Much less noticeable, but equally ubiquitous is the hydration of ions holding on to several water molecules in nanoscopic pores or in natural air at low relative humidity. Such hydration of ions with a high ratio of ions to water molecules (up to 1:1) are essential in determining the energetics of many physical and chemical systems. Herein, we present a quantitative analysis of the energetics of ion hydration in nanopores based on molecular modeling of a series of basic salts associated with different numbers of water molecules. The results show that the degree of hydrolysis of basic salts in the presence of a few water molecules is significantly different from that in bulk water. The reduced availability of water molecules promotes the hydrolysis of divalent and trivalent basic ions (S₂^?, CO₃^2?, SO₃^2?, HPO₄^2?, SO₄^2?, PO₄^3?), which produces lower valent ions (HS^?, HCO₃^?, HSO₃^?, H₂PO₄^?, HSO₄^?, HPO₄^2?) and OH^?ions. However, reducing the availability of water inhibits the hydrolysis of monovalent basic ions (CN^?, HS^?). This finding sheds some light on a vast number of chemical processes in the atmosphere and on solid porous surfaces. The discovery has wide potential applications including designing efficient absorbents for acidic gases.     

Tunable Multicolor Phosphorescence of Crystalline Polymeric Complex Salts with Metallophilic Backbones

A total of 35 [Au(NHC)₂][MX₂] (NHC=N‐heterocyclic carbene; M=Au or Cu; X=halide, cyanide or arylacetylide) complex salts were synthesized by co‐precipitation of [Au(NHC)₂]⁺ cations and [MX₂]^? anions. These salts contain crystallographically determined polymeric Au???Au or Au???Cu interactions and are highly phosphorescent with quantum yields up to unity and emission color tunable in the entire visible regions. The nature of the emissive excited states is generally assigned to ligand (anion)‐to‐ligand (cation) charge‐transfer transitions assisted by d¹⁰???d¹⁰ metallophilicity. The emission properties can be further tuned by controlled triple‐component co‐crystallization or by epitaxial growth. Correct recipes for white light‐emitting phosphors with quantum yields higher than 70 % have been achieved by screening the combinatorial pool.