Freezing temperatures of aqueous solutions of hexamethylenetetramine with polyols,amides, and ethers

Freezing temperatures of dilute aqueous solutions of hexamethylenetetramine and mixtures of hexamethylenetetramine with myo-inositol, d-mannitol, cyclohexanol, formamide, acetamide, 1,4-dioxane, and 1,3,5-trioxane have been measured. These data yield pairwise molecular Gibbs energies of interaction between the molecules in an aqueous solution. Using the additivity principle, the results also yield the pairwise functional group Gibbs energies of interaction in an aqueous solution for the amine nitrogen with itself and with the hydroxyl, amide, ether, and methylene groups.     

Freezing temperatures of aqueous solutions of mixtures of amides and polyols. Gibbs energy of interaction of the amide group with the hydroxyl group in aqueous solution

Freezing temperatures of dilute aqueous mixtures of: formamide with myo-inositol, d-mannitol, and cyclohexanol; N,N-dimethylformamide with inositol, mannitol, and cyclohexanol; and acetamide with inositol and mannitol have been measured. These data have been analyzed to yield the pairwise molecular Gibbs energies of interaction between the molecules in an aqueous solution. Using the group additivity principle, the results yield the pairwise functional group Gibbs energies of interaction of the amide group with the hydroxyl group, G _OH,CONH =–31 J-kg-mol^–2.     

Interactions in aqueous nonelectrolyte systems. Gibbs energy of interaction of the ether group with the hydroxyl group and the amide group

Freezing temperatures of dilute aqueous solutions of equimolar mixtures of 1,3,5-trioxane with myo-inositol, d-mannitol, cyclohexanol, formamide, and acetamide, and 1,4-dioxane with myo-inositol, d-mannitol, formamide, and acetamide have been measured. These data yield pairwise Gibbs energies of interactions between the molecules in an aqueous solution. Using the group additivity principle, the results also yield the pairwise functional group Gibbs energies of interaction for the ether group with the hydroxyl and amide group. These results have been combined with all available data from the literature to yield the Gibbs energy and enthalpy of interaction of amides, ethers, alcohols, and saccharides in aqueous solution.To whom correspondence should be addressed.     

Freezing temperatures of aqueous solutions of methyl formate and ethyl acetate with a variety of nonelectrolytes. Gibbs energy of interaction of the ester group with other functional groups

Freezing temperatures of dilute aqueous solutions of ethyl acetate and mixtures with myo-inositol, D-mannitol, formamide, 1,3,5-trioxane, 1,4-dioxane, acetamide, hexamethylenetetramine, and methyl formate have been measured. In addition, freezing temperatures of dilute aqueous solutions of methyl formate and mixtures with the above solutes have been measured. From these data, the pairwise molecular Gibbs energies of interaction between the molecules were calculated. Using the additivity principle, the pairwise functional group Gibbs energies of interaction were calculated for ester group interactions with a variety of other functional groups.     

Freezing points and enthalpies of dilute aqueous solutions of tetrahydropyran, 1,3-dioxane, 1,4-dioxane,and 1,3,5-trioxane. Free energies and enthalpies of solute-solute interactions

The enthalpies of dilute aqueous solutions of tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,2,5-trioxane, and an equimolal mixture of tetrahydropyran and 1,3,5-trioxane were measured at 25°C and at molalities from about 0.1 to 1.0 mol kg¹. The freezing points of the same aqueous solutions (except for 1,3-dioxane) were measured over a similar molality range. The results were used to calculate the enthalpies and Gibbs free energies of the pair-wise interactions of the above solutes in dilute aqueous solutions at 25°C. From these results, the additivity principle proposed by Savage and Wood was used to get the Gibbs free energy and enthalpies of interaction for the ether-ether and ether-methylene groups. Because of the limited number of measurements, the interaction parameters were not determined with great precision. Nevertheless, the standard errors for the predicted enthalpies and Gibbs free energies are quite reasonable. The signs and magnitudes are similiar to those determined for other polar groups.     

Gibbs energies of interaction of the CH2 and CHOH groups from freezing point data for aqueous binary mixtures of D-mannitol,myo-inositol,and cyclohexanol

Freezing temperatures of dilute aqueous solutions of D-mannitol, myo-inositol, D-mannitol + myo-inositol, D-mannitol + cyclohexanol, and myo-inositol + cyclohexanol have been measured over the concentration range 0.1 to 1.0 mol-kg^–1. These data yield pairwise molecular Gibbs energies of interaction which have been corrected to 25°C and treated according to the Savage-Wood additivity principle to give pairwise functional group Gibbs energies of interaction for CH₂/CH₂, CH₂/COOH, and CHOH/CHOH. Anomalous behavior of some systems is discussed in terms of the interactions.     

甘氨酸从水到酰胺衍生物水溶液中的迁移焓

用RD496-Ⅱ型微量热量计测定了298.15 K甘氨酸在N-甲基甲酰胺（NMF）,N, N-二甲基甲酰胺（DMF）,N-甲基乙酰胺（NMA）,N, N-二甲基乙酰胺（DMA）水溶液中的溶解焓,计算了甘氨酸从水到四种酰胺衍生物水溶液中的迁移焓（ΔtrH）。根据结构水合作用模型讨论了酰胺的结构对甘氨酸迁移焓的影响。实验结果表明：甘氨酸在酰胺衍生物水溶液中的迁移焓均为正值,并且随着溶液浓度增大而增大。比较甘氨酸在甲酰胺（FA）和乙酰胺（AD）水溶液中的迁移焓,发现在不同酰胺水溶液中迁移焓大小为：DMA>NMA>DMF>NMF>AD>FA。甘氨酸与甲酰胺之间以亲水-亲水相互作用为主,与其它酰胺之间以亲水-疏水作用为主。     

The aromatic amino acid behaviour in aqueous amide solutions

The enthalpies of solution of L-phenylalanine in the mixtures of water with the protein denaturant urea have been measured in the temperature range of 288.15–318.15 K. Using the results of the present research and literature data of free energies, the standard thermodynamic functions of the solute transfer from water to aqueous urea solutions have been estimated in a wide temperature range. The enthalpic, heat capacity, entropic and free energy parameters of the solute-urea pair and triplet interactions have been computed. The amino acid — amide pair interaction was found to be attractive in the temperature range studied due to the favourable enthalpic term. The triplet interaction being slightly repulsive reveals the enthalpic origin also. The examination of the Savage and Wood additivity-of-groups approach does indicate the inapplicability of this scheme to enthalpies and entropies of interaction. It has been found for the first time that the heat capacity of interaction changes its sign at 303 K, i.e. the temperature dependence of enthalpic and entropic parameters passes through the pronounced extrema near the temperature of the minimum of the heat capacity of pure water.     

The enthalpies of dilution of pyridine and methylpyridine at 298.15 K

The enthalpies of dilution of aqueous solutions for pyridine and methylpyridine isomers have been determined with a 2277-Thermal Activity Monitor at 298.15 K. The results have been treated using the excess function concept and homotactic interaction coefficients have been obtained. The homotactic enthalpic pairwise interaction coefficients are discussed qualitatively in terms of substitution effects of methyl group introduced into the pyridine ring.     

Excess enthalpies of solution of primary and secondary alcohols in dodecyldimethylamine oxide micellar solutions

The excess enthalpies of solution with respect to water of some primary and secondary alcohols in dodecyldimethylamine oxide (DDAO) micellar solutions were measured by mixing aqueous solutions of alcohols with surfactant solutions. Standard free energies, enthalpies and entropies were obtained from the distribution of alcohols between aqueous and micellar phases. It is shown that thermodynamics of transfer of secondary alcohols from aqueous to the DDAO micellar phase differ slightly from those of their corresponding primary alcohols, that the additivity rule holds for free energies of transfer and that enthalpy and entropy display convex curves. The present data are compared with those from the aqueous to the dodecyltrimethylammonium bromide (DTAB) micellar phases and to the literature data for transfer from water to octane. The role of the hydrophilic interactions between OH group and the micellar head groups and of the hydrophobic interactions between the methylene group and its apolar environment is evidenced.     

The enthalpies of interaction of glycine with some alkan-1-ols in aqueous solutions at 298.15 K

Enthalpies of dissolution of glycine (G) in aqueous solutions of methanol (MeOH), ethanol (EtOH), propan-1-ol (PrOH) and butan-1-ol (BuOH) at 298.15 K have been measured. The enthalpic pair interaction coefficients of glycine zwitterion and alkan-1-ol molecules were determined by using standard solution enthalpies of glycine in water and aqueous solutions of alkan-1-ols.     

Thermodynamics of micellization of alkyldimethylbenzylammonium chlorides in aqueous solutions

Specific conductivities of alkyldimethylbenzylammonium chlorides (alkyl=decyl-, dodecyl-, tetradecyl-, and hexadecyl-) in aqueous solutions were measured as a function of molality and temperature. Critical micelle molalities (cmc) and degrees of ionization of the micelles, beta, were estimated from the dependence of the specific conductivity on molality. It was found that temperature dependence of cmc is U-shaped with a minimum shifting toward higher temperatures with a decrease in the chain length of the alkyl group. The temperature dependence of ln xcmc (where xcmc is the cmc in mole fraction units) was fitted to the equation of Muller, which we modified by taking into account the temperature dependencies both of beta and of change in heat capacity upon micellization. From the fitting parameters, Gibbs free energies, enthalpies, and entropies of micellization as a function of temperature were estimated.     

Enthalpies of dilution of aqueous solutions of amides and alcohols

Enthalpies of dilution of aqueous systems containing formamide, dimethyl-formamide, the mixture of these amides, and each amide separately with mannitol, inositol, and cyclohexanol have been determined at 25°C. The data have been treated in terms of the Savage-Wood additivity principle and in combination with literature data. New values for the methylene-amide, carbinol-amide, and amide-amide group interaction enthalpies are presented. These may be used with data on a wider variety of solute systems to obtain interaction enthalpies for new groups.     

Calorimetric determination of enthalpies,gibbs energies,and entropies of inclusion of some alcohols into α- and β-cyclodextrins in aqueous solutions

The enthalpies of transfer of cyclohexanol from aqueous to aqueous - or -cyclodextrin solutions have been measured at various mole fractions at 298.15 K on a rocking twin-microcalorimeter of heat-conduction type and the molar enthalpies, Gibbs energies, and entropies of inclusion in the aqueous solutions have been determined by the method proposed by the authors [Netsu Sokutei 10, 103 (1983)], to elucidate the driving force of the molecular inclusion. Discussions are given for all the systems obtained by the authors, concluding that the driving force is the enhancement of the entropy.Calorimetric studies on molecular inclusion V.     

Enthalpies of dilution of aqueous systems containing hexamethylenetetramine and other nonelectrolytes

Enthalpies of dilution of aqueous systems containing hexamethylenetetramine, alone and in ternary system with each of mannitol, myoinositol, cyclohexanol, formamide, dimethylformamide, and trioxane have been determined. The data have been treated in terms of the Savage-Wood additivity principle and first estimates for the pairwise groups interaction enthalpies of N/N, CH₂/N, CHOH/N, COHN/N and –O–/N have been made. The results are discussed in light of all other known group interaction enthalpies. The limitations and utilities of the Savage-Wood principle are reviewed.     

Temperature dependence of complex formation constants in aqueous solutions of metal acetates

The equilibrium constants of formation of inner- and outer-sphere cation-anion complexes (ion pairs) in aqueous solutions of different metal acetates in a wide temperature range have been calculated by integrating the density function of distribution of ligands around the cation. The standard Gibbs energies, enthalpies, and entropies of formation of 1: 1 complexes have been calculated. It has been shown that, in all solutions under consideration, contact and solvent-separated ion pairs coexist. A conclusion has been drawn that the temperature dependence of ion association constants is mainly determined by the temperature dependence of the water dielectric constant.     

Solubilization of methane,ethane, propane andn-butane in aqueous solutions of sodium dodecylsulfate

The solubilities of methane, ethane, propane, and n-butane were measured in aqueous solutions of sodium dodecylsulfate (NaDS) (0–0.1M) from 15 to 27°C. From these measurements the standard Gibbs energies, entropies, and enthalpies for the process of transferring the solute molecules from the gaseous phase into the solutions were calculated. An approximate relationship was found relating the volume fraction of the micelles to NaDS concentration.     

The dilution enthalpies of l-prolinol in N,N-dimethylformamide aqueous solutions at T = 298.15 K

Values of the enthalpy of dilution were measured for l-prolinol in pure water and N,N-dimethylformamide (DMF) aqueous solutions with various mass fractions of DMF at T = 298.15 K using a flow-mixing microcalorimeter. A pseudo phase equilibrium model was proposed to simplify the complex aggregation equilibrium and interpret the abnormality in the dilution enthalpy, which together with the McMillan–Mayer approach was used to fit the experimental data to obtain the enthalpic pairwise interaction coefficients and the molar aggregation enthalpies of l-prolinol in DMF aqueous solutions. The results are discussed in terms of the hydrophobic interaction and the interactions between the solvated solutes.     

Enthalpies of interaction of glycine with some amides in aqueous solutions at 298.15 K

The dissolution enthalpies of glycine in aqueous solutions of acetamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylformamide, N,N-diethylformamide and N,N-diethylacetamide were measured at 298.15 K. The enthalpic pair interaction coefficients of glycine zwitterion-amide molecules were determined by using standard solution enthalpies of glycine in water and aqueous solutions of amides. The additivity of groups concept of Savage and Wood was used to estimate the contribution of each of the functional groups of the studied amides.     

D-山梨醇在纯水和卤化钠水溶液中293.15K～318.15K的稀释焓

应用流动式等温精密微量热技术测定4个温度(293.15、303.15、308.15和318.15 K)下D-山梨醇在纯水和卤化钠水溶液中的稀释焓.根据改进的McMillan-Mayer理论对所测数据进行关联,得到了表观摩尔稀释焓对浓度变化的经验方程和各阶焓相互作用系数(h2,h3和h4)和二阶熵相互作用系数(s2),根...