Thermodynamic and spectroscopic properties of 2-pyrrolidinones. 2. Dielectric properties of 2-pyrrolidinone in binary mixtures

Dielectric permittivities of 2-pyrrolidinone - acetone, -dimethyl sulfoxide,-2-propanol, -dichloromethane and -water systems were measured as a function of mole fraction over the whole composition range at 30 and 50°C. The excess dielectric permittivities are predominantly negative for all the mixtures and the excess molar polarizations are negative except for 2-pyrrolidinone - water and 2-pyrrolidinone - dimethyl sulfoxide mixtures. The large negative excess quantities are indicative of the strong specific interactions between the like and unlike components of the solution mixtures.     

Kinetics of hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution as a function of temperature near the temperature of maximum density,and the isochoric controversy

At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of such isochoric temperatures show no unique features. Taken together with previously published kinetic data for the hydrolysis of a range of simple organic solutes in both water and D2O near their respective TMDs, we conclude that special significance in the context of rates of chemical reactions in aqueous solutions should not be attached to the isochoric condition.     

The influence of cyclic alcohols on the temperature of maximum density of water

The effect of a homologous series of cyclic monohydric alcohols (C₄−C₈) on the temperature of maximum density of water has been examined. The structural contribution to the shift in the temperature of maximum density (TMD) is positive (increased structuredness) for alcohols up to C₆ but becomes negative at C₈. The behavior is compared with that of linear monohydric alcohols and Ω-diols.     

Determination of the intermolecular interaction parameters in the water-amide systems based on the data of the excess thermodynamic functions

The molar excess enthalpiesH ^E for the water +N-methyl-2-pyrrolidinone binary mixtures have been measured as functions of mole fraction at 298.15, 308.15 and 318.15 K, using isoperibol rotating calorimeter. A hydrogen bonding pairs model proposed by Luzar was fitted to the experimental dataH ^E,G ^E for the binary mixtures of water with hexamethylphosphoric triamide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidinone.     

Studies on reactions of some ruthenium sulfoxide bipyridyl complexes with 1,4-bis(salicylidene)phenylenediamine ligand used as spacer

A dinucleating spacer 1,4-bis(salicylidene)phenylenediamine (SALPHEN) derived from 1,4-phenylenediamine and salicylaldehyde has been synthesized and characterized. The ruthenium(II) sulfoxide derivative of 2,2′-bipyridine or 1,10-phenanthroline on reaction with this ligand resulted in the formation of eight dinuclear complexes, which were characterized by elemental analyses, conductivity measurements, magnetic susceptibility, FT-IR, fast atom bombardment-mass spectra, electronic spectroscopy, ¹H-NMR, ¹³C{¹H}-NMR, and ²D-NMR spectra (HETCOR). The prepared complexes have two different formulations, [{trans-RuCl₂(so)(N–N′)}₂(μ-SALPHEN)] and [{cis-RuCl₂(so)(N–N′)}₂(μ-SALPHEN)], where so?=?dimethyl sulfoxide (DMSO)/tetramethylene sulfoxide (TMSO), N–N′?=?2,2′-bipyridine/1,10-phenanthroline, and SALPHEN?=?1,4-bis(salicylidene)phenylenediamine. Two moles of ruthenium sulfoxide bipyridine precursor were coordinated to the bidentate SALPHEN through nitrogen. All the complexes possess antibacterial activity against Escherichia coli in comparison to Chloramphenicol.     

Thermodynamic and dynamic anomalies for a three-dimensional isotropic core-softened potential

Using molecular-dynamics simulations and integral equations (Rogers-Young, Percus-Yevick, and hypernetted chain closures) we investigate the thermodynamics of particles interacting with continuous core-softened intermolecular potential. Dynamic properties are also analyzed by the simulations. We show that, for a chosen shape of the potential, the density, at constant pressure, has a maximum for a certain temperature. The line of temperatures of maximum density (TMD) was determined in the pressure-temperature phase diagram. Similarly the diffusion constant at a constant temperature, D, has a maximum at a density rho(max) and a minimum at a density rho(min) < rho(max). In the pressure-temperature phase diagram the line of extrema in diffusivity is outside of the TMD line. Although this interparticle potential lacks directionality, this is the same behavior observed in simple point charge/extended water.     

Viscosity and Excess Viscosity of Dilute Aqueous Solutions of Ethylenediamine,Trimethylenediamine and N,N -Dimethyltrimethylenediamine

Viscosities of the systems, water (W) + ethylenediamine (ED), W + trimethylenediamine (TMD) and W + N , N -dimethyltrimethylenediamine (DMTMD) were determined from 303.15 to 323.15 K and in the composition range, 0 h X 2 h 0.45, where X 2 is the mole fraction of solutes. On addition of the solutes to water the viscosities increase sharply, pass through maxima and then decline; the heights of maxima vary as, W + DMTMD > W + TMD > W + ED. The maxima occur at X 2 0.225, 0.300 and 0.325 for the systems, W + DMTMD, W + TMD and W + ED, respectively. The position of maximum of a particular system remains unchanged with temperature. The rapidly ascending part of viscosity curves is accounted for by the combined effect of hydrophobic hydration and hydrophilic effect, while the declining part of the curves is thought to be due to predominance of hydrophobic interaction.     

Novel poly(pyridine imide) with pendent naphthalene groups: Synthesis and thermal,optical, electrochemical,electrochromic, and protonation characterization

A new diamine containing a pyridine heterocyclic group and a naphthalene substituent, 4-(2-naphthyl)-2,6-bis(4-aminophenyl) pyridine (NBAPP), was synthesized with the Chichibabin reaction and used in the preparation of poly(pyridine imide) by direct polycondensation with 4,4′-hexafluoroisopropylidenediphathalic anhydride in N-methyl-2-pyrrolidinone (NMP). The poly(pyridine imide) derived from diamine NBAPP with naphthalene substituents was highly organosoluble: it was soluble in tetrahydrofuran, NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, and γ-butyrolactone at room temperature and in pyridine, dimethyl sulfoxide, and cyclohexanone upon heating at 70 °C. The poly(pyridine imide) was converted into lightly colored, optically transparent, flexible, and tough polyimide films via casting onto glass from a DMAc solution. This polymer exhibited good thermal stability (temperature of 10% weight loss = 527 °C) in air and high dielectric constants (as high as 4.20 at 1 kHz). The polyimide films had a tensile strength of 102 MPa and a tensile modulus of 1.8 GPa. As for the optical properties, the polymer exhibited UV–vis absorption bands in the region of 223–450 nm and possessed strong green-yellow fluorescence (500 nm) after being protonated with acid. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2367–2374, 2007     

Common features of orientational order at the temperature of maximum density for various water models: molecular dynamics study

Canonical ensembles for liquid water were obtained from molecular dynamics simulations at various temperatures using the TIP5P, TIP4P-FQ, TIP4P, and SPC/E water models at a fixed density of 1 g/cm3. From these ensembles, it was found that the distributions of the orientational order parameter q of these models showed similar patterns as temperature changed except that the distributions were shifted relative to each other by the difference of their temperature of maximum density (TMD). The four models exhibited similar distributions and average values of orientational order around their respective TMDs, and these common features were investigated in detail especially. The current study suggests that the unique microscopic configuration of water molecules cause TMD phenomenon in any reasonable water model. This finding provides a useful tool in the development of new water potentials by offering guidelines to predict the TMD, avoiding troublesome isothermal-isobaric ensemble simulations.     

Validation and application of orientational order-based TMD prediction

Through our recent examination of four famous water models, we hypothesized that there should be common features of orientational order universally at the temperature for maximum density (TMD) of 1 g/cm³ whatever reasonable water model used. However, it was derived empirically rather than theoretically and it demands more severe tests eagerly to be a common law. In the present work, we tested two additional water models, TIP4P-2005 and TIP5P-Ew models developed recently. From this, we found the consistent common features of orientational order around reported values of TMD again. To demonstrate simple yet effective predictability of an unknown TMD for a certain water model using the method derived from our hypothesis, simulations of our method were carried out at several temperatures with intervals of 20 °C for TIP4P-ice model. In spite of its much less computational cost and temperature range that was chosen arbitrarily, TMD was predicted correctly with resolution of 20 °C at least. We propose that our method offers a useful guideline for TMD by narrowing down the choice of TMD candidates without heavy computational efforts, at least for point-charge water models.     

Chemically Crosslinked pH- and Temperature-Sensitive (N-isopropylacrylamide-co-1-vinyl-2-pyrrolidone) Based on New Crosslinker: I. Swelling Behavior

Novel pH- and temperature-sensitive polymer matrices based on N-isopropylacrylamide have been developed. The hydrogels were prepared by bulk radical polymerization of N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone in appropriate amounts of distilled water using different mol% of traditional N,N-methylene bisacrylamide (MBA) and the new synthesized N,N,N-tris acryloyl melamine (MAAm) crosslinkers. Lower critical solution transition temperatures (LCST) were measured by differential scanning calorimetry. The synthesized hydrogels have LCST lower than 40°C. The influence of environmental conditions such as temperature and pH on the swelling behavior of these polymeric gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity. The crosslinked NIPAAm/VP with MAAm hydrogels exhibited more rapid deswelling rate than NIPAAm/VP hydrogels crosslinked with MBA in pure water in response to abrupt temperature changes from 20°C to 50°C.     

The influence of substituted alcohols on the temperature of maximum density of water

The influence of various substituted (including halogenated) alcohols on the temperature of maximum density (TMD) of water has been investigated. Evaluation of the structural contribution to the shift in the TMD demonstrates that trifluoroethanol, hexafluoroisopropanol, and neopentyl alcohol are structure makers, whereas trichloroethanol and tribromoethanol are structure breakers. The results are discussed in terms of an excluded volume model.     

The influence of aliphatic diols on the temperature of maximum density of water

The influence of various aliphatic diols on the temperature of maximum density (TMD) of water has been investigated. 1,2-Propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2,5-hexanediol were found to yield positive structural contributions to the solute-induced shift in the TMD, i.e., they are structure makers. Contrariwise, data from the literature indicate that 1,2-ethanediol is a structure breaker. Relationships between the structure making/breaking tendencies of the solutes and the relative positions of the two hydroxyl groups are discussed.     

Preferential Solvation in Mixed Solvents

The Kirkwood–Buff integrals and the volume-corrected preferential solvation parameters for the first solvation shell of binary mixtures of tetrahydrofuran with many organic solvents, calculated from reported thermodynamic data at the temperatures for which these data were available, are reported. The co-solvents include c-hexane, methyl-c-hexane, n-heptane, i-octane, benzene, toluene, ethylbenzene, 1-chlorobutane, dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane, tetrachlorom-ethane, tetrachloroethene, hexafluoro benzene, ethanol, 1-propanol, 2-propanol, dibutyl ether, acetic acid, acetone, dimethyl sulfoxide, tetramethylene sulfone (sulfolane), acetonitrile, pyrrolidine, and triethylamine. The preferential solvation parameters of these mixtures are discussed in terms of the interactions that occur.     

Thermodynamic activation parameters for viscous flow of dilute aqueous solutions of ethylenediamine,trimethylenediamine and N,N-dimethyltrimethylenediamine

The density and the viscosity data have been used to determine the thermodynamic activation parameters, free energies (ΔG ^?), enthalpies (ΔH ^?) and entropies (ΔS ^?), for viscous flow of the systems; water (W) + ethylenediamine (ED), W + trimethylenediamine (TMD) and W + N,N-dimethyltrimethylenediamine (DMTMD) in the temperature range of 303.15–323.15 K over the composition range of 0 ≤ X ₂ ≤ 0.45, where X ₂ is the mole fraction of diamines. On addition of diamines to water, ΔG ^?, ΔH ^? and ΔS ^? values increase sharply, pass through a maximum and then decline. The heights of maximum in the ΔG ^? versus X ₂ curve vary as, W + DMTMD > W + TMD > W + ED. For all systems, the excess properties, ΔG ^{? E} , ΔH ^{? E} and ΔS ^{? E} are positive. The observed increase in thermodynamic values may be due to combined effect of hydrophobic hydration of diamines and water–diamine interaction as a result of hydrophilic effect.     

Steric effects control the structure of the solvated lanthanum(III) ion in aqueous, dimethyl sulfoxide, and N,N'-dimethylpropyleneurea solution. An EXAFS and large-angle X-ray scattering study

The structure of the solvated lanthanum(III) ion has been determined in aqueous, dimethyl sulfoxide, and N,N'-dimethylpropyleneurea solution by means of the EXAFS and large-angle X-ray scattering (LAXS) techniques. The close agreement between the EXAFS spectra of solid nonaaqualanthanum(III) trifluoromethanesulfonate and of an aqueous lanthanum(III) perchlorate solution shows that the hydrated lanthanum(III) ion in aqueous solution most probably has the same structure as in the solid, i.e., nine water molecules coordinated in a tricapped trigonal prismatic configuration. The data analysis from EXAFS and LAXS measurements of the aqueous solution resulted in the La-O bond distances 2.52(2) and 2.65(3) A to the water molecules in the prism and the capping positions, respectively. The LAXS study shows a second hydration sphere consistent with approximately 18 water molecules at 4.63(2) A. The EXAFS spectra of solid octakis(dimethyl sulfoxide)lanthanum(III) trifluoromethanesulfonate and a dimethyl sulfoxide solution of this salt are also similar. The data analysis of EXAFS and LAXS measurements assuming eight-coordination around lanthanum yielded an La-O bond distance of 2.50(2) A, and an La...S distance of 3.70(3) A, giving an La-O-S angle of 133(2) degrees. The EXAFS data of an N,N'-dimethylpropyleneurea solution of lanthanum(III) trifluoromethanesulfonate gave the La-O bond distance 2.438(4) A and the La...C distance 3.41(2) A, which correspond to an La-O-C angle of 131(2) degrees. The La-O bond distance is consistent with seven-coordination around lanthanum, on the basis of the variation of the ionic radii of the lanthanum(III) ion with different coordination numbers.     

Characterization of para‐substituted benzamidoximes and benzamidinium salts by 15N NMR spectroscopy

¹⁵N NMR data for a series of 12 para‐substituted benzamidoximes and benzamidinium salts were determined in dimethyl sulfoxide. For the amino group of benzamidoximes ¹J(N,H) coupling constants were determined using polarization transfer techniques; the other ¹⁵N atoms were not detectable owing to fast exchange processes and, thus, standard proton noise decoupled spectra had to be measured. The ¹⁵N NMR chemical shifts of the oxime‐type nitrogen atom and the benzamidinium amino group (with two exceptions) correlate with Hammett σ° values (r²>0.95). ¹⁵N NMR shift data are a suitable and sensitive means for characterizing far‐ranging electronic substituent effects in these functional groups. Additionally, ¹³C NMR data in dimethyl sulfoxide solution are given. All spectroscopic data will be used for investigations into the mechanisms of the enzymes involved in the metabolic cycle of oxidation and reduction of benzamidines and benzamidoximes. Copyright © 2002 John Wiley & Sons, Ltd.     

Water effect on the gelation behavior of polyacrylonitrile/dimethyl sulfoxide solution

The gelation behavior of polyacrylonitrile (PAN)/dimethyl sulfoxide (DMSO) solution containing different amounts of water has been investigated using various methods. The ternary phase diagram of PAN/DMSO/water system indicated that water enhanced the temperature at which phase separation of PAN/DMSO solution occurred. Intrinsic viscosities [η] of dilute PAN/DMSO solution and PAN/DMSO/water solution at varied temperatures were measured to examine the influence of water on the phase behavior of PAN/DMSO solution. The presence of water in the solution gave rise to elevated critical temperature T_c. The gelation temperature T_g obtained by measuring the loss tangent tan δ at different oscillation frequencies in a cooling process was found to increase with increased water content in the solution. The critical relaxation exponent n value, however, changed little with varied concentration. During the aging process, the gelation rate of PAN/DMSO solution increases with the water level. The n values of the PAN/DMSO solutions with 2 wt% and 4 wt% water were a little larger than that of the solution without water, which may be explained by the turbid gel resulted from phase separation. The n values obtained in the aging process were larger than those obtained in the cooling process for the same three solutions, ascribed to the weaker gel with less cross-linking points formed in long time. Water led to the formation of denser gel structure. The coarser gel surface can also be attributed to the phase separation promoted by water.     

The synthesis, characterisation, phase behaviour and swelling of temperature sensitive physically crosslinked poly(1-vinyl-2-pyrrolidinone)/poly(N-isopropylacrylamide) hydrogels

Physically crosslinked complexes of polyvinyl pyrrolidinone-poly (N-isopropylacrylamide) (PVP-PNIPAAm) were prepared by photopolymerisation from a mixture of the monomers 1-vinyl-2-pyrrolidinone and N-isopropylacrylamide. IR spectroscopy and calorimetry were used to characterise the resulting xerogels. By alternating the monomer feed ratio, copolymers were synthesised to have their own distinctive lower critical solution temperature (LCST). The transition temperature of the gels was established using cloud point measurement and modulated differential scanning calorimeter (MDSC). This ability to shift the phase transition temperature of the copolymers provides excellent flexibility in tailoring transitions for specific uses. Swelling experiments were performed on the copolymer disks in distilled water at varying temperatures to establish the behaviour of the gels above and below phase transition temperature. The results obtained show that below transition temperature, the gels are water soluble but above this temperature they are slightly less water soluble; significantly less water soluble; or water insoluble; depending on the composition and LCST of the gel.     

Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6-methylmercaptopurine riboside-κN⁷)(nitrato-κ²O,O′)silver(I) 2.32-hydrate, [Ag(NO₃)(C₁₁H₁₄N₄O₄S)₂]·2.32H₂O. The crystal structure, determined from synchrotron diffraction data, shows a central Ag^I ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via atom N7 (purine numbering), with the nitrate counter-ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three-dimensional network by hydrogen bonding.