Pure Non-aqueous Solvents Research Articles

A Conductometric study of complexation reaction between dibenzyl-14-crown-4, with ZrO2+ in some binary mixed nonaqueous solvents

In Some binary methanol mixtures, (MeOH), 1,2 dichloroethane (DCE), acetonitrile (AN), and tetrahydrofuran (THF), with dimethylformamide (DMF) at different temperatures using the conductometric process, the reaction of macrocyclic ligand to complexation, dibenzyl-14-crown-4 (DB14C4) with ZrO2+ cation was examined. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between (DB14C4) and ZrO2+ cation is 1:1 (M:L). The stability order of (DB 14C4.ZrO)2+complex in pure non-aqueous solvents was found to be: [AN], [DCE], [MeOH], [THF], [DMF]. A non-linear behaviour was observed improvements in log Kf of (DB14C4.ZrO)2+ complex or Binary mixed solvent composition, It Was clarified as to the Interactions with solvents and even solvents in terms of the hetero-selective solving of the ecosystem affected by complexation response. The obtained results show that the stability of (DB14C4.ZrO)2+ complex is sensitive to the composition of the mixed solvent. The values of thermodynamic parameters ΔH°cand ΔS°c) for the formation of (DB14C4.ZrO)2+complex using van’t Hoff maps, the stability constant was obtained from temperature dependence. The results show that in most cases, the (DB 14C4.ZrO)2+complex is enthalpy destabilized but entropy balanced and the values and signs of thermodynamic parameters are often These are decided by nature and composition of the mixed solvents.

A Conductometric Study of Complexation Reaction between Kryptofix 22DD with Yttrium(III) Cation in Some Binary Mixed Non-aqueous Solvents

The complexation process between Y3+ cation and kryptofix 22DD was studied in ethyl acetate–dimethylformamide (EtOAc–DMF), ethyl acetate–methanol (EtOAc–MeOH), ethyl acetate–nitromethane (EtOAc–NM) and ethyl acetate–dimethylsulfoxide (EtOAc–DMSO) binary mixtures at different temperatures by using conductometric method. The conductance data show that in most cases, the stoichiometry of the complex formed between the macrocyclic ligand and the Y3+ cation is 1 : 1 [ML]. But in some systems such as, in the case of EtOAc–DMSO (90 mol % DMSO) binary solvent solution, in addition to formation of a 1 : 1 (ML) complex, a 1 : 2 (ML2) complex is formed in solution, which shows that the stoichoimetry of complexes may be changed by the nature of the medium. The stability order of (kryptofix 22DD · Y)3+complex in the studied binary solvent solutions at 25°C was found to be: EtOAc–MeOH > EtOAc–DMF > EtOAc–DMSO and in the case of pure non-aqueous solvents at 25°C it was: EtOAc > MeOH > DMF ∼ NM. A density functional theory (DFT) study of the interaction of yttrium(III) cation with kryptofix 22DD in the liquid phase for the pure organic solvents was performed. The results are in reasonably good agreement with the experimental data. A non-linear behavior was observed for changes of log Kf of (kryptofix 22DD · Y)3+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the preferential solvation of the species involved in the complexation reaction.

Large Swelling Capacities of Crosslinked Poly(N-isopropylacrylamide) Gels in Organic Solvents

ABSTRACTPNIPAM hydrogels are widely studied materials which swell in a great extent in water and water like solvents (e.g. alcohols). The hydrophilic nature of PNIPAM networks is very attractive however it is an important disadvantage at the moment of encapsulating hydrophobic drugs, which minimize their use in other fields. In this work we studied the swelling in different solvent mixtures with water and also in pure nonaqueous solvents, some of them immiscible with water. Accordingly, PNIPAM gels swell strongly in highly polar solvents (e.g. chloroform) but it does not swell in slightly polar solvents (e.g. toluene). The main interaction between the solvent and the polymer chain seems to involve the hydrogen bonding with the amide group, according to the calculated Hansen parameters (δh). It is possible to swell the gel in binary or ternary mixtures containing toluene. In that way, non-polar substances can be loaded inside the gel to change its properties. As a proof of concept, polyaniline (PANI) solubilized in chloroform using camphorsulfonate as solubilizing counterion. The obtained nanocomposites become sensitive to pH changing color and conductivity when exposed to basic or acidic aqueous solutions.

Study of Kryptofix5 Complexation with La3+ Cation in Several Individual and Binary Nonaqueous Solvents Using Conductometric Method

Complexatio of the La3+ cation with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane(Kryptofix5) was studied in pure solvents acetonitrile (AN), methanol (MeOH), nitrobenzene (NB), tetrahydrofuran (THF), methyl acetate (MeOAC) and in various binary solvent mixtures of AN–MeOH, AN–NB, AN–THF, and AN–MeOAC systems at different temperatures using the conductometric method. The stoichiometry of the complex was found to be 1 : 1 (ML). In all cases, the variation of the log kf with composition of the solvent was non-linear. This behavior is probably due to a change in the structure of these binary mixed solvents as the composition of the medium is varied. The stability order of the complex in pure nonaqueous solvents at 25°C increases in the order: AN > THF > MeOAC > MeOH > NB. The values of thermodynamic data (ΔH c °,ΔS c °) formation of (Kryptofix5.La)3+ complex are definitely solvent dependent.

Solvent influence upon complex formation between kryptofix5 and Cd2+ in some pure and binary mixed non-aqueous solvents using conductometry

The complexation reaction of Cd2+ with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (kryptofix5) was studied in pure acetonitrile (AN), ethylacetate (EtOAc), methanol (MeOH), dimethylformamide (DMF), and in acetonitrile-ethylacetate (AN–EtOAc), acetonitrile-dimethylformamide (AN–DMF), methanol-acetonitrile (MeOH–AN), and dimethylformamide-ethylacetate (DMF–EtOAc) binary mixed solvent solutions at different temperatures using conductometric method. The conductance data show that the stoichiometry of the complex in all solvent systems, is 1 : 1 [ML]. The fitting and experimental curves were obtained from Sigma plot computer program to make it more clear of the 1 : 1 [ML] complexation model. The stability constant of (kryptofix5·Cd)2+ complex was obtained using a GENPLOT computer program. The results show that the stability of (kryptofix5·Cd)2+ complex at all studied temperatures in the binary solvent solutions decreases in order: AN–EtOAc > AN–MeOH > AN–DMF ∼ EtOAc–DMF and in pure non-aqueous solvents, the stability order of the complex was found to be: AN > EtOAc > MeOH > DMF. The values of standard thermodynamic parameters (, ) for formation of the complex were obtained from temperature dependence of the stability constant using the van’t Hoff plot. The results show that in most cases, the complex formation reaction between kryptofix5 and Cd2+ is entropy stabilized.

Complexation ability of kryptofix 22DD with lanthanum (III) cation in some binary mixed non-aqueous solvents

The complex formation between lanthanum (III) cation with kryptofix 22DD was studied in acetonitrile–dimethylformamide (AN–DMF), acetonitrile–methanol (AN–MeOH), acetonitrile–ethylacetate (AN–EtOAc) and acetonitrile–ethanol (AN–EtOH) binary solvent solutions at different temperatures by using conductometric method. The conductance data show that in all cases, the stoichiometry of the complex formed between the macrocyclic ligand and the metal cation is 1:1 [ML]. The stability order of (kryptofix 22DD.La)3+ complex in the studied binary solvent solutions at 25 °C was found to be: AN–EtOAc>AN–EtOH>AN–MeOH>AN–DMF and in the case of pure non-aqueous solvents at 25 °C was: EtOAc>EtOH>MeOH>AN>DMF. A non-linear behavior was observed for changes of logKf of (kryptofix 22DD.La)3+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the preferential solvation of the species involved in the complexation reaction. The values of standard thermodynamic parameters (∆H c°, ∆S c°) for formation of (kryptofix 22DD.La)3+ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots.The results show that in most cases, the (kryptofix 22DD.La)3+ complex is enthalpy destabilized, but entropy stabilized and the values of these thermodynamic quantities for formation of the complex are quite sensitive to the nature and composition of the mixed solvents solution.

Study of complexation process between 4′-nitrobenzo-15-crown-5 and yttrium(III) cation in binary mixed non-aqueous solvents using conductometric method

The complexation reaction of macrocyclic ligand (4′-nitrobenzo-15C5) with Y3+ cation was studied in acetonitrile-methanol (AN-MeOH), acetonitrile-ethanol (AN-EtOH), acetonitrile-dimethylformamide (AN-DMF) and ethylacetate-methanol (EtOAc-MeOH) binary mixtures at different temperatures using conductometry method. The conductivity data show that in all solvent systems, the stoichiometry of the complex formed between 4′-nitrobenzo-15C5 and Y3+ cation is 1: 1 (ML). The stability order of (4′-nitrobenzo-15C5). Y3+ complex in pure non-aqueous solvents at 25°C was found to be: EtOAc > EtOH > AN ≈ DMF > MeOH, and in the case of most compositions of the binary mixed solvents at 25°C it was: AN≈MeOH ≈ AN-EtOH > AN-DMF > EtOAc-MeOH. But the results indicate that the sequence of the stability of the complex in the binary mixed solutions changes with temperature. A non-linear behavior was observed for changes of logKf of (4′-nitrobenzo-15C5 · Y3+) complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent interactions and also the hetero-selective solvation of the species involved in the complexation reaction. The values of thermodynamic parameters (ΔHcℴ and ΔScℴ) for formation of the complex were obtained from temperature dependent of the stability constant using the van′t Hoff plots. The results represent that in most cases, the complex is both enthalpy and entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.

A conductometric study of complexation reaction between dibenzo-24-crown-8 with yttrium cation in some binary mixed non-aqueous solvents

The complexation reaction of macrocyclic ligand, dibenzo-24-crown-8 (DB24C8) with Y+3 cation was studied in some binary mixtures of methanol (MeOH), ethanol (EtOH), acetonitrile (AN) and tetrahydrofuran (THF) with dimethylformamide (DMF) at different temperatures using the conductometric method. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between DB24C8 and Y+3 cation is 1:1 (ML). The stability order of (DB24C8.Y)+3 complex in pure non-aqueous solvents was found to be: AN > EtOH > MeOH > DMF. A non-linear behaviour was observed for changes of log Kf of (DB24C8.Y)+3 complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the heteroselective solvation of the species involved in the complexation reaction. The obtained results show that the stability of (DB24C8.Y)+3 complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (∆H°c and ∆S°c) for formation of (DB24C8.Y)+3 complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the (DB24C8.Y)+3 complex is enthalpy destabilized but entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.

A thermodynamic study of interaction of Na+ cation with benzo-15-crown-5 in binary mixed non-aqueous solvents

The complexation reaction between benzo-15-crown-5 (B15C5) with Na+ cation was studied in acetonitrile–methanol (AN–MeOH), tetrahydrofuran–methanol (THF–MeOH), acetonitrile–tetrahydrofuran (AN–THF) and nitromethane–dimethylformamide (NM–DMF) binary mixtures at different temperatures using conductometry method. The conductometric data show that in most cases, the stoichiometry of the complex formed between B15C5 and Na+ cation is 1:1 (ML), but in the cases of AN–THF (mol%THF = 65.7) binary mixture and in pure THF, a 1:2 (ML2) complex is formed in solutions, which shows that the stoichiometry of the complexes may change by the nature of the medium. The stability constant of the resulting 1:1 complex in pure non-aqueous solvents decreases in the order: AN > MeOH > DMF. The thermodynamic parameters (ΔH°c and ΔS°c) for formation of (B15C5.Na)+ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex is both enthalpy and entropy stabilized. A non-linear behavior was observed for changes of log Kf of (B15C5.Na)+ complex versus the composition of the binary mixed solvents, which was explained on the basis of changes occurring in the structure of the mixed solvents and also the preferential solvation of the cation, ligand and the resulting complex in solutions.

Self-assembled coating for modification of the electro-osmotic flow in nonaqueous capillary electrophoresis using formamide

The use of pure nonaqueous solvents in capillary electrophoresis (CE) can alter the separation selectivity and enhance the solubility of hydrophobic compounds and enables the use of higher voltages. However, control of the electro-osmotic flow (EOF) is essential. In this work, we report the use of self-assembled coatings for EOF modification and elimination of analyte adsorptions onto silica capillaries in pure formamide. Bilayer capillary coatings derived from the double chain cationic surfactant dimethyldioctadecylammonium bromide (2C18DAB) reverses the EOF in buffers such as acetate, formate, and phosphate. Reversed EOF of >1.1 × 10–4 cm2/Vs enables the separation of the pharmaceutical drugs propranolol, metoprolol, chloroquine, and chloropheniramine in less than 5 min with efficiencies of 0.2–0.5 million plates/m (66 000 to 165 000 plates). Chemical and physical factors affecting the coating stability and their influence on separation speed and efficiency of the cationic drugs in formamide are also investigated.Key words: capillary electrophoresis, cationic surfactants, electro-osmotic flow, formamide, nonaqueous solvents.

Solvent effects on reverse micellisation of Tween 80 and Span 80 in pure and mixed organic solvents

Reverse micellisations of nonionic surfactants (Tween 80 and Span 80) in various pure nonaqueous solvents like carbontetrachloride, benzene, toluene, chloroform, cyclohexane and xylene, and in mixed solvent systems like CCl4-DMF and CCl4-DMSO covering the low dielectric range, are studied by UV electronic spectroscopy at 25°C. Micellar aggregation number (n s ) in various solvents is evaluated using the hydrophobic dye, Oil Red. 0. The critical micellar concentration (cmc) andn s ) dependencies on the solvent dielectric, solvent ionization potential, solvent-surfactant interaction potentials, mole fractions of solvents in mixtures and internal pressures are studied. The CCl4-DMSO system shows acmc increase effect, while the CCl4-DMF system shows acmc decrease effect and the excess functions of CCl4-DMSO and CCl4-DMF show increase and decrease effects respectively. Rationalisations of the results and the role of the solvent cage effect have been discussed.

Critical micelle concentration of some sorbitan fatty acid esters—effect of solvents

The critical micelle concentrations (CMC) of sorbitan monopalmitate and sorbitan monooleate have been determined at 25/sup 0/C in pure nonaqueous solvents like benzene and carbon tetrachloride, and also in a solvent mixture comprised of diesel oil and paraffin oil (50:50). An attempt has been made to correlate CMC data with the surfactant solvent interaction concept and the effect of the aromatic vs. aliphatic nature of the solvent is highlighted. The importance of unsaturation in the hydrophobic moiety in bringing up the CMC also is indicated.

Thermodynamics of solution of gaseous tetramethyltin in 36 solvents. Comparison of experimental results with cavity-theory calculations

The standard free energy of solution of Me4Sn(g) in 36 pure solvents has been determined by gas-chromatographic head-space analysis. Calorimetrically determined enthalpies of solution of liquid Me4Sn have been combined with the known enthalpy of vaporisation of Me4Sn to yield values of the enthalpy, and thence the entropy, of solution of Me4Sn(g) in 28 pure non-aqueous solvents. It is shown that values of ΔS°s do not vary greatly with the non-aqueous solvent. Attempts have been made to calculate values of ΔG°s, ΔH°s and ΔS°s for Me4Sn(g) in a number of solvents by use of SPT or SRMR calculations of cavity terms and Lennard-Jones or Kirkwood–Muller calculations of interaction terms. Similar calculations have been carried out for a range of non-polar, gaseous solutes in a few selected solvents.

Hydrophobic nitroxide radicals as probes to investigate the hydrophobic interaction

The EPR spectrum of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) has been systematically investigated in several solvents and in aqueous solutions of glycerol,t-BuOH, Bu4NBr,n-HexNH3Br,n-OctNH3Br, NaBPh4, and Ph4AsCl. Most of the results have been obtained at 25°C, though the temperature dependence of the linewidths has been examined in water and several organic solvents. Data on the spectrum of ditertiarybutylnitroxide in aqueous solutions of glycerol and Bu4NBr are also presented. The spectrum was simulated to determine WH, the linewidth after allowance for the unresolved proton hyperfine interaction, in each manifold of the triplet due to the nitrogen hyperfine interaction. The linewidth WH is analyzed in terms of the reorientational correlation time Aθ and the angular velocity correlation time AJ. In most solutions Aθ is determined only by the bulk solution viscosity, except in situations where significant clustering of hydrophobic solute molecules occurs. In pure nonaqueous solvents the temperature dependence results are consistent with AJ being determined by the bulk viscosity, while in water or aqueous solutions, a very different behavior is found which is interpreted as a manifestation of clathrate-like hydration of the hydrophobic radical. This interpretation is incorporated in a two-state model developed to account for the WH data of TEMPO in aqueous solutions of various hydrophobic solutes. The equilibrium parameters derived from the model, for the association of TEMPO with several hydrophobic solutes, support the concept of hydrophobic interactions as pictured from thermodynamic excess functions.