Infrared studies of fluoroalcohol-base complexes in the gas phase,carbon tetrachloride solutions and argon matrices

Hydrogen bonded complexes of fluoroalcohols with oxygen-containing bases like dimethyl ether and alkanols have been investigated in argon matrices, in CCl₄ solutions and in the gas phase. The increase of the proton donor capacities with succesive substitution of fluorine atoms into the alkyl group of alcohols is indicated by a strong increase of the shift Δν of the OH stretching frequency in the complexes. For alkanols as acceptors, an increase of Δν is observed along the series CH₃OH, CH₃CH₂OH, (CH₃)₂CHOH, and (CH₃)₃CHOH. The frequency shifts Δν increase as one passes from the gas phase to CCl₄ solutions and argon matrices.     

Topological investigations of molar excess volumes of quinoline with alkanols

Excess volumes V ^E of binary liquid mixtures of quinoline with alkanols have been determined from densities at 30°C as a function of composition. The excess volumes are negative over the whole mole fraction range for all the mixtures and decrease with increasing length of alkanol (C₁–C₁₀). The V^E data have been analyzed in terms of an approach which uses graph theoretical connectivity parameters of the third degrees for two components. The analysis gives information regarding associated species in the pure state and in the mixture. It is suggested that, in the mixture state, no change occurs in the association of alkanols.     

Transfer Volumes of Small Peptides from Water to Aqueous Xylitol Solutions at 298.15 K

Densities have been measured by an oscillating-tube densimeter for aqueous solutions of glycylglycine and glycylglycylglycine in aqueous xylitol solutions with xylitol mass fractions ranging from 0 to 0.15 at 298.15 K. Apparent molar volumes and limiting partial molar volumes have been used to calculate the corresponding transfer volumes from water to different concentrations of xylitol + water mixtures. The results are interpreted in terms of the cosphere overlap model.     

Interactions of Some Amino Acids with Aqueous Osmoprotectant Proline at 298.15 K: Volumetric and Calorimetric Studies

Apparent molar volumes of a homologous series of amino acids in aqueous proline solutions have been obtained from densities at 298.15 K, measured with a vibrating-tube digital densimeter. These data have been used to deduce the partial molar volumes of transfer from water to aqueous proline solutions; these partial molar volumes of transfer are found to be positive for glycine, alanine, α-amino-n-butyric acid and valine, whereas they are negative for leucine. The number of water molecules hydrated to the amino acids was estimated from the partial molar volume data. In order to supplement this information, enthalpies of transfer of aqueous amino acids from water to 0.1, 2.25 and 1 mol⋅dm⁻³ aqueous proline have been determined at 298.15 K using a VP-ITC titration calorimeter. The data on the partial molar volumes and enthalpies of transfer are discussed in terms of various interactions operating in the ternary mixtures of amino acids, water and proline.     

Interactions of Peptides and Lysozyme with Aqueous Tetraethylammonium Bromide at 298.15 K

The apparent molar volumes, V _{ø, 2}, of gly-leu, gly-gly-leu and the partial specific volume ν^° of hen-egg-white lysozyme have been determined in aqueous of TEAB solutions by density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volumes V _2,m ^o for the peptides in aqueous TEAB solutions and the standard partial molar volumes of transfer Δ_tr V _2,m ^o of the peptides from water to aqueous TEAB solutions. The results on Δ_tr V _2,m ^o of peptides from water to aqueous TEAB solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophilic and hydrophobic-hydrophobic group interactions. In order to supplement this information, enthalpies of transfer of aqueous peptides from water to TEAB solution have been determined at 298.15 K using a VP-ITC titration calorimeter. The data on partial molar volumes and enthalpies of transfer have been discussed in light of various interactions operating in the ternary system of peptides, water and TEAB. The partial specific volume of transfer of lysozyme from water to aqueous TEAB solutions also indicates the predominance of hydrophobic interactions.     

Partial molar volumes of l-alanine,dl-serine,dl-threonine,l-histidine,glycine, and glycylglycine in water,NaCl, and DMSO aqueous solutions at T = 298.15 K

The apparent molar volumes of l-alanine, dl-serine, dl-threonine, l-histidine, glycine, and glycylglycine in water and in the aqueous solutions of NaCl and DMSO with various concentrations at T = 298.15 K have been measured by the precise vibrating-tube digital densimeter. The calculated partial molar volumes at infinite dilution have been used to obtain corresponding transfer volumes from water to various solutions. The experimental results show that the standard partial molar volumes of the above amino acids and peptide at the dilute DMSO aqueous solutions are very close to those in water. However, the volumes show several types of variations with the increase of the concentrations of DMSO due to different types of side chain of amino acids, which should be discussed specifically. The NaCl changes considerably the infinite dilution standard partial molar volumes of the above amino acids and peptide in the aqueous solutions. The infinite dilution standard partial molar volumes of the each amino acids and peptide increase with the concentrations of NaCl. The experimental results have been rationalized by a cosphere overlap model.     

氨基酸在水或氯化钾水溶液中体积性质的研究

在298.15K和常压下利用密度法测定了十几种α-氨基酸在水或氯化钾水溶液中的表观摩尔体积, 由此得到了各氨基酸的偏摩尔体积和其相应的转移偏摩尔体积,以及氨基酸中侧链对其偏摩尔体积的贡献值。从理论上计算了各氨基酸在上述溶液浓度的增加而增大; 氨基酸共溶质间的相互作用以1:1形式为主; 氨基酸的水化数随盐浓度的增加而减小。对所得结果进行了定性讨论。     

Cu-Catalyzed Oxidative Phosphorylation of Alkanols with White Phosphorus and H 2 O 2

Oxidative phosphorylation of alkanols with white phosphorus in the presence of catalytic amounts of CuCl 2 has been effected. The reaction proceeds in the aqueous H 2 O 2 --HCl system exothermically to form dialkylphosphites and trialkylphosphates in a total yield of up to 35%. Conditions for selective synthesis of dialkylphosphites in moderate yield have been found.     

Experimental study and modelling using the ERAS-Model of the excess molar volume of acetonitrile–alkanol mixtures at different temperatures and atmospheric pressure

Densities of {(1−x)CH₃(CH₂)_n−1OH + xCH₃CN} for n=1, 2, 3 or 4 have been determined as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure using a vibrating-tube densimeter (Anton Paar DMA 4500, resolution 1×10⁻⁵ g cm⁻³). Excess molar volumes were calculated. The V_m^E values were negative for acetonitrile–methanol mixtures and sigmoid for acetonitrile–alkanols (C₂–C₄) mixtures over the complete mole fraction range. V_m^E values increase in a positive direction with increase in chain length of the alkanols and with the temperature. The Extended Real Associated Solution Model (ERAS-Model) calculations allowing for self-association for the alkanols and complex formation between acetonitrile and alkanols have been used to correlate experimental data. The model is able to reproduce the asymmetrical V_m^E behavior of the studied systems, although agreement between theoretical and experimental values is less satisfactory for some concentration ranges.     

Aggregation and clouding behavior of aqueous solution of EO-PO block copolymer in presence of n-alkanols

The aqueous solution behavior of an ethylene oxide-propylene oxide triblock copolymer Pluronic^® P123 [(EO)₂₀(PO)₇₀(EO)₂₀] was investigated in the presence of various n-alkanols (C₁-C₆) by cloud-point, viscosity, dynamic light scattering (DLS) and spectroscopic (FTIR, NMR) measurements. For lower alkanols (methanol, ethanol and 1-propanol), the cloud-points (CPs) increased with increase in alkanol concentration. The reverse effect was found for higher alkanols (C₄-C₆) where both the CPs and critical micelle temperatures (CMTs) decreased with increase in concentration. This behavior is explained in terms of a co-operative association of higher alkanols and block copolymers by replacing water molecules in the PPO core and inducing micellar growth in aqueous P123 solution. Lower alkanols are likely to be good solvents for both PEO and PPO blocks and the effect on PPO blocks predominates indicating an increase in CP and CMT with increase in alkanol concentration.     

Thermodynamic properties of binary liquid mixtures involving weak interactions Part 1. Excess volumes of binary mixtures of 1-chlorobutane with normal alkanols at 303.15 K

Chandramouli, J., Choudary, N.V., Krishnaiah, A. and Naidu, P.R., 1982. Thermodynamic properties of binary liquid mixtures involving weak interactions. Part 1. Excess volumes of binary mixtures of 1-chlorobutane with normal alkanols at 303.15 K. Fluid Phase Equilibria, 8: 87–92Excess volumes for binary mixtures of 1-chlorobutane with 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol have been determined at 303.15 K. V^E is positive over the whole range of composition for the mixtures of 1-chlorobutane with 1-propanol and 1-butanol. An inversion in the sign of V^E is observed over certain ranges of concentration of the halogenated alkane in the remaining four mixtures. The results are explained in terms of depolymerisation of hydrogen-bonded alcohol aggregates, decrease in dipolar association, and weak hydrogen-bonding interaction of the type Cl- - - HO between unlike molecules.     

甘氨酸在尿素、甲脲及二甲脲水溶液中的体积性质

用精密数字密度计测定了甘氨酸在不同质量分数的尿素、甲脲和二甲脲水溶液中的密度,计算了甘氨酸的极限偏摩尔体积、迁移偏摩尔体积、理论水化数和体积作用系数,讨论了溶剂组成变化对甘氨酸迁移偏摩尔体积和理论水化数的影响.结果表明,甘氨酸与尿素及烷脲分子间的相互作用主要以1:1的形式为主.尿素、甲脲、二甲脲分子与氨基酸荷电中心的直接相互作用,削弱了两性离子带电中心对周围水分子的电致收缩效应,造成了理论水化数随溶液浓度的增加而减小.     

Study of micropores accessibility in coals and activated carbon using immersion heats with C1–C4 alkanols

Two natural coals and a sample of activated carbon were studied with respect to micropores accessibility for C1–C4 alkanols using immersion calorimetry. From the immersion enthalpies, micropores volumes were calculated according to the Stoeckli–Kraehenbuehl (SK) equation, and obtained values were compared with the surface characteristics of gas adsorption measurements. Validity of the SK equation was found to be problematic for natural coals giving micropores volumes up to three times exceeding those of the CO₂ adsorption measurements. Reason for such discrepancy is discussed, with specific interactions between coals and alkanols likewise marked swelling of coals in the presence of alkanols being recognised as possible explanation. A drop in immersion heats with branched butanols was generally observed, enabling at least semi-quantitative evaluation of the abundance of micropores with diameters below ca. 0.7 nm that are inaccessible for tert-butanol.

     

甘氨酸、L-丙氨酸和L-丝氨酸在尿素水溶液中的体积性质

蛋白质的折叠与解折叠、稳定性、变性行为和酶的活性等都受到环境中其它各种物质影响.作为蛋白质模型分子,氨基酸在混合溶液中的热力学研究近年来引起了广泛重视.尿素在生物体系中的独特地位主要表现在:它是水结构的破坏者,同时又是许多球状蛋白的变性剂.然而,尿素对球状蛋白的变性作用尚未达成共识.     

用SEC柱和胶束流动相分离小分子的模型

 使用体积排阻色谱 (SEC)柱和胶束流动相成功地分离了一些小分子化合物 ,给出了分离模型。这种分离方式是基于胶束和水相在色谱过程中的不同迁移以及溶质在胶束和水相间的不同分配而实现的 ,其分离的机制与胶束电动色谱 (micellar electrokinetic chromatography,MEKC)十分相似。理论处理的结果表明 ,溶质的保留体积与胶束浓度有关 ;通过溶质的保留体积可得到溶质在胶束和水相间的分配系数。还采用了两种不同的 SEC柱分离了一些脂肪醇 ,验证了这一理论模型 ,测定了它们的分配系数 ,结果表明两种柱测得的小分子醇在胶束和水相中的分配系数具有较好的一致。     

Viscosity of the systems m-xylene, +1-propanol, +2-propanol, +1-butanol, +t-butanol

Viscosities, η, of the systems, m-xylene, +1-propanol, +2-propanol, +1-butanol and +t-butanol have been measured for the whole range of composition at 303.15, 308.15, 313.15, 318.15 and 323.15?K. The variation of viscosities has been plotted against mole fraction of alkanols. Viscosities have been found to increase slowly up to a considerable concentration of alkanols, followed by a rapid rise of viscosities at higher concentrations. The slow rise of viscosity is attributed to dissociation of alkanols in m-xylene, while the rapid rise of viscosity is ascribed to self-association of alkanols. Excess viscosities, η^E, have been plotted as a function of mole fraction of alkanols. The curves show negative values for the whole range of composition, with minima occurring in alkanol-rich region.?η?and η^E have been fitted to appropriate polynomial equations. The study shows the effect of branching and chain length of alkanols on?η?and η^E.     

298.15 K甘氨酰二肽在乙酸钠水溶液中的体积性质

测定了298.15 K三种甘氨酰二肽(甘氨酰甘氨酸、甘氨酰-L-缬氨酸和甘氨酰-L-亮氨酸)在0.5, 1.0, 1.5和2.0 mol•kg－1乙酸钠水溶液中的密度, 计算了这些肽在乙酸钠水溶液中的表观摩尔体积, 标准偏摩尔体积, 标准偏摩尔转移体积, 理论水化数和体积相互作用参数. 结果表明: 甘氨酰二肽的标准偏摩尔体积和标准偏摩尔转移体积均随乙酸钠浓度的增加而增大, 溶液中离子与肽带电基团/甘氨酰基团(CH2CONH)之间的相互作用大于离子与肽的非极性基团间的相互作用, 乙酸钠和甘氨酰二肽之间主要是对相互作用. 利用共球交盖模型对所研究的肽与乙酸钠之间的体积相互作用进行了解释. 利用氨基酸的标准偏摩尔体积值, 对二肽的标准偏摩尔体积进行了估算, 发现计算值与实验值一致.     

Influence of CTAB/alkanol/cyclohexane w/o microemulsions on the basic hydrolysis of crystal violet

The basic hydrolysis of crystal violet has been studied in w/o microemulsions of the CTAB/alkanols/cyclohexane system (alkanols: 1-butanol and 1-hexanol). The reaction can be considered to occur in the water phase of the droplets and from the rate constant the apparent dielectric constant of the water phase was determined. The cyclohexane incorporation in the system produces a decrease in the effective dielectric constant of the water phase and in the specific conductivity.     

Investigations of the Properties of l-Histidine in Aqueous NaCl Solutions at Different Temperatures

Density and viscosity experimental data for l-histidine in NaCl aqueous solutions were obtained at different salt and different amino acid concentrations in the range of temperatures between 293.15 and 323.15 K. The results have been correlated and analyzed in order to evaluate the influence of electrolyte concentration and temperature on the volumetric and viscometric properties of the solutions. The apparent molar volumes and the transfer volumes of l-histidine in aqueous NaCl solutions at different salt and amino acid molalities over entire temperature range were calculated from experimental density data. The viscosity experimental data have been analyzed with Jones–Dole equation and the Falkenhagen (A) and the Jones–Dole coefficient (B) have been calculated in order to evaluate the interactions occurring in the systems. The B viscosity coefficients were found to be positive for all conditions, showing a kosmotropic effect of solutes, indicating an alignment of zwitterions with ions/water dipoles. A comparison of standard partial molar volumes for some amino acids in water and NaCl aqueous solutions shows that they increase with molecular mass and complexity of the lateral side chain of the amino acid.