Partial molar volumes of amino acid derivatives in water

The partial molar volumes at infinite dilution for a number of hydrochlorides and sodium salts of N-methyl derivatives of , -aminocarboxylic acids in water at 25°C are measured and related to their van der Waals volumes. Results indicate that 4.96±0.48 water molecules hydrate a betaine hydrochloride. Volumes of proton ionization and interaction terms are evaluated. Group contributions to the partial molar volumes are also reported.     

Volumetric properties of the octyl methoxycinnamate + ethyl acetate solvent system at several temperatures

In this article, the excess molar volumes and partial molar volumes of components of the binary system octyl methoxycinnamate (OMC)?+?ethyl acetate (AcOEt) were investigated from density measurements on the entire range of mass fractions for this system at 298.15, 303.15, 308.15, 313.15, and 318.15?K. The results of excess molar volumes were fitted by the Redlich–Kister equation using third degree polynomials. The system exhibited negative excess volumes (up to ?0.926?cm³?mol^?1 at 318.15?K), probably due to interactions like dispersion forces between unlike molecules or some differences in the molar volumes of pure components. The effect of temperature on the different volumetric properties studied was also analysed. Besides, the volumetric thermal expansion coefficients were also calculated finding values varying from 7.53?×?10^?4?K^?1 for pure OMC up to 1.38?×?10^?3?K^?1 for pure AcOEt at 308.15?K.     

Excess Molar Volumes and Partial Molar Volumes for Binary Mixtures of Water With 1,2-Ethanediol, 1,2-Propanediol,and 1,2-Butanediol at 293.15, 303.15 and 313.15 K

Abstract

From dilatometric method at 293.15,303,15, and 313.15K for binary mixtures of water and 1,2-alkane diols, the excess molar volumes, V^E and the partial molar volumes, V _i of both components at 293.15 K have been obtained as a function of mixtures composition. Excess molar volumes were calculated and correlated by a Redlich-Kister type function in terms of mole fraction. The partial molar volumes have been extrapolated to zero concentration to obtain the limiting values at infinite dilution, V ⁰ _i . All mixtures showed negative values and decreases with the chain length of diols. The values become less negative with increasing temperature. The results are explained in terms of dissociation of the self-associated diol molecules and the formation of aggregates between unlike molecules.     

Partial molal volumes of ions in organic solvents. IV. Ethylene glycol

Apparent molal volumes have been measured for several electrolytes in ethylene glycol (EG) and the standard state partial molal volumes, V₂°, evaluated. Ultrasonic vibration potentials (uvp) have also been measured for most of the alkali metal halides in EG, and these employed to evaluate ionic partial molal volumes, V° (ion). The results show unambiguously that the uvp is essentially independent of solvent viscosity. The V₂° data have also been divided into ionic components by four other techniques including, the method of Mukerjee, the use of Ph₄AsBPh₄, the correspondence method and an extrapolation of V₂° for a series of tetraalkylammonium bromides as a funtion of cation molecular weight. With the exception of the latter technique, all methods used give 30±2 cm³-mol^–1 for V° (ion), although the uvp leads to the largest value for V° (ion). The divisions have been analyzed also with the aid of Hepler's equation, and the results suggest that the uvp method gives a more accurate division and that the EG dipole is more hindered than the dipole in ethanol.     

Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules.     

甘氨酸在多元醇-水混合溶剂中的体积性质

利用精密数字密度计测定了甘氨酸分别在不同组成的乙二醇 水和丙三醇 水混合溶剂中的密度,计算了甘氨酸的表观摩尔体积、极限偏摩尔体积和理论水化数.根据结构水合作用模型讨论了迁移偏摩尔体积的变化规律,并与乙醇 水体系作了比较. 结果表明,甘氨酸分子在醇 水混合溶剂中增体积效应的大小与醇分子所含OH基数目的多少有关,但最直接也是最重要的影响因素是其水合壳层的结构形态. 乙醇 水体系中的增体积效应特别显著与该溶剂结构变化上的微观不均匀性和不连续性有关.     

Thermodynamics of mixtures with strongly negative deviations from Raoult’s law: Part 5. Excess molar volumes at 298.15 K for 1-alkanols+dipropylamine systems: characterization in terms of the ERAS model

Excess molar volumes, V_m^E, at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with dipropylamine are reported from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the whole mole fraction range, indicating strong interactions between unlike molecules, which are more important for the system involving methanol, characterized by the most negative V_m^E. For the remainder mixtures, V_m^E at equimolar composition, is approximately constant. The V_m^E curves are nearly symmetrical.

V_m^E and excess molar enthalpies, H_m^E, of the mixtures studied are consistently described by the ERAS model. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in the methanol+dipropylamine system.     

Volumetric Properties of N, N-Dimethylformamide with 1,2-Alkanediols at 20°C

Dilatometric measurements of excess molar volumes and excess partial molar volumes have been made for binary mixtures of N, N-dimethylformamide with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2- pentanediol, and 1,2-hexanediol at 20°C over the entire composition range. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through C = O ... 3H-O hydrogen bonding. Further, the effects of difference in chain lengths and steric factors on molecular interactions are also examined. From the experimental results, excess molar volumes were calculated and correlated by a Redlich–Kister type function in terms of mole fractions.     

Volumetic Properties of Glycerol with N,N-Dimethylformamide and with Water at 25 and 35°C

Densities of glycerol + N,N-Dimethylformamide (DMF) and glycerol + water mixtures have been measured over the full range of compositions at 25 and 35°C. Excess molar volumes and excess partial molar volumes, of each system have been calculated. All mixtures show negative values of the excess molar volume due to increased interactions between unlike molecules.     

Thermodynamics of aqueous mixtures of nonelectrolytes. I. Excess volumes of water-n-alcohol mixtures at several temperatures

Excess volumes of binary mixtures of water with methanol, ethanol and 1-propanol were obtained from density measurements at 5 degree intervals from 15 to 35°C over the entire composition range. Excess thermal expansion coefficients, partial molar excess volumes, and expansibilities at 25°C were derived from the results. The significance of these values is discussed in relation to hypothesized structural changes in the mixtures.     

Partial molar volumes of organic compounds in water. VI. α,ω-diaminoalkane hydrochlorides

Measurements of the partial molar volumes in water at 25°C of the mono-and dihydrochlorides of the ,-diaminoalkanes, up to a chain length of 10 carbon atoms, are reported. Volumes of ionization have been determined and the electrostriction of the solvent calculated. Effects of the substituents are felt up to the -carbon atom, but thereafter are only very weak or nonexistent.     

The influence of correlation of molecular orientations and of molecular flexibility on excess volumes of mixtures of branched and linear alkanes

It is shown that the excess volumes of mixtures of alkanes are not only influenced by equation-of-state effects, but also by differences in orientational order and, probably, in flexibility of the component molecules.     

Volumetric Properties of Binary Mixtures of Isomeric Butanols and C8 Solvents at 298.15 K

Excess molar volumes, V _m ^E, over the whole composition range for binary mixtures of 1-butanol, 2-butanol, and 2-methyl-2-propanol + 1-octanol, or 2-octanol, or di-n-butyl ether, or n-hexylacetate were determined at 298.15 K from density measurements carried out with a vibrating-tube densimeter. Small V _m ^E values, both positive and negative, are displayed by mixtures containing 1- or 2-octanol, whereas positive and larger values are always found for mixtures containing dibutyl ether and hexylacetate. These results can be justified in terms of H-bonding interactions and/or steric hindrance due to the branched alkyl chains. Partial molar volumes at infinite dilution of the isomeric butanols in the C8 compounds were also calculated from the apparent molar volumes in dilute solution. The solute-solvent interactions and the effects of the local organisation of the solvent around the butanol molecules were discussed using the void and cavity volumes as different estimates of the intrinsic volume of the molecules. The volumetric behavior of butanols seems to be determined by the solute-solvent interactions rather than packaging effects.     

Molar and partial molar excess volumes of di-n-butylamine with chloroalkanes at 25°C

Molar excess volumes and partial molar excess volumes are reported for binary mixtures of dibutylamine+dichloromethane, trichloromethane and tetrachloromethane at 25°C, over the whole concentration range. A comparative study is made between the primary and secondary amines and their mixtures with chloroalkanes. The applicability of the so-called ERAS model for predicting thermodynamic excess properties is tested here for excess molar volumes; the calculated values agree quite well with experimental data.     

The true physical meaning of the corrected retention volumes in GC

Summary Through a straightforward mathematical derivation it is shown that the compressibility correction factor equals the ratio of gas pressure at the column outlet to the average pressure in the column, . Therefore, by multiplying by this factor, the experimentally measured retention volumes can be recalculated to the average pressure in the column. Corrected retention volumes thus represent the volume of the mobile phase under real conditions of chromatography in the column. Appropriate definitions for corrected retention volumes and factorj are formulated.     

Apparent molar heat capacities and volumes,van der Waals volumes and accessible surface areas of alkylated derivatives of cytosine and uracil in aqueous solutions at 25°C.

Densities and specific heat capacities of aqueous solutions: 1,3,5,6-tetramethyluracil, 1,6-dimethyl-3-ethyluracil, 1,6-dimethyl-3-propyluracil, 1,6-dimethyl-3-butyluracil, 1,N⁴-trimethylcytosine, 1,N⁴-dimethyl-5-ethylcytosine, 1,N⁴ dimethyl-5-propylcytosine, 1,N⁴-dimethyl-5-butylcytosine were determined using flow calorimetry and flow densimetry at 25°C. Apparent molar volumes and heat capacities, van der Waals volumes and accessible surface areas were determined. It was stated that for alkylcytosines and alkyluracils partial molar volumes and heat capacities correlate linearly with the number of substituted methylene groups-CH₂-as well as with the van der Waals volumes and accessible surface areas of the compounds studied; for cyclooligouracils the cyclization effect was discussed.     

Amide-water interactions in cosolvent systems. I. Solubilities and apparent molar volumes of methyl paraben

Solubility and apparent molar volume data are used to demonstrate effects of amide alkylation on amide-water interactions at 25° C. Precise measurements were made of the apparent molar volumes of the amides in binary amide-water mixtures using a dilatometric technique. The results show that the apparent molar volumes of alkyl-substituted amides in water pass through a minimum at an amide concentration which varies inversely with the degree of alkylation. Further studies showed that the solubilities of methyl paraben (methyl-p-hydroxybenzoate) and naphthalene in various amide-water solvent systems increased in characteristic fashion with amide alkylation.     

Volume and compressibility changes of complex formation between 18-Crown-6 and NaCl,KCl, and CsCl in water

The apparent molal volumes and compressibilities of NaCl, KCl, and CsCl in mixtures of 18-Crown-6 and water have been calculated from density and speed-of-sound measurements at 25°C. The partial molal volumes and compressibilities of the salts when all cations have formed complexes with 18-Crown-6 molecules have been evaluated. The sign and magnitude of the volume and compressibility changes of complex formation strongly suggest that the charge of the cation becomes very effectively screened by the crown ether.     

Excess and partial excess molar volumes of 1,4-dichlorobutane with butanols at 25 and 40°C

From density measurements over the whole composition range at 25 and 40°C excess molar volumes for binary mixtures of 1,4-dichlorobutane with l-butanol, 2-butanol, 2-methyl-l-propanol or 2-methyl-2-propanol are calculated. V^E results were fitted by the method of least squares to a smoothing equation. Excess partial molar volumes and limiting excess partial molar volumes at 25° are also calculated.