Thermodynamics of Organic Mixtures Containing Amines. II. Excess Molar Volumes at 25°C for Methylbutylamine + Alkane Systems and Eras Characterization of Linear Secondary Amine + Alkane Mixtures

Excess molar volumes, at 25°C and atmospheric pressure for methylbutyl amine + n-hexane; + cyclohexane; + n-octane; n-decane; + n-dodecane; + n-tetradecane, or + n-hexadecane systems are reported from densities measured with a vibrating-tube densimeter. The excess functions, molar enthalpy, and volume, for linear secondary amine + n-alkane systems are discussed in terms of interactional and structural effects. In addition, these solutions, which include amines from dimethyl to dioctylamine, are studied in the framework of the ERAS model. The corresponding ERAS parameters are reported. The agreement between experimental data and ERAS results is good for excess enthalpies, excess Gibbs energies, and excess molar volumes. The larger discrepancies are found for the excess volumes when strong free-volume effects are present in the investigated mixtures. The variation with temperature of the thermodynamic properties is well described by ERAS.     

Reaction rates for O + HD → OH + D and O + HD → OD + H

We have calculated reaction rates for the reactions O + HD → OH + D and O + DH → OD + H using improved canonical variational transition state theory and least-action ground-state transmission coefficients with an ab initio potential energy surface. The kinetic isotope effects are in good agreement with experiment. The optimized tunneling paths and properties of the variational transition states and the rate enhancement for vibrationally excited reactants are also presented and compared with those for the isotopically unsubstituted reaction O + H₂ → OH + H. The thermal reactions at low and room temperature are predicted to occur by tunneling at extended configurations, i.e., to initiate early on the reaction path and to avoid the saddle point regions. Tunneling also dominates the low and room temperature reactions for excited vibrational states, but in these cases the results are not as sensitive to the nature of the tunneling path. Overbarrier mechanisms dominate for both thermal and excited-vibrational state reactions for T > 600 K. For the excited-state reaction (with initial vibrational quantum number n > 0) a transition state switch occurs for T > 1000 K for the O + HD(n = 1) → OD + H case and for T > 1500 K for the O + DH(n = 1) → OD + H reaction, and this may be a general phenomenon for excited-state reactions at higher temperature. In the present case the switch occurs from an early variational transition state where the vibrationally adiabatic approximation is expected to be valid to a tighter variational transition state where nonadiabatic effects are probably important and should be included.     

Diagramme d'equilibre liquide-liquide de systemes binaires pyridine+n-alcanes

Résumé Liquid-liquid phase diagrams have been determined for binary systems of pyridine+n-hexane, pyridine+n-heptane and pyridine+n-dodecane. A general quasi-chemical theory in terms of group surface interactions has been applied to compute these liquid-liquid phase diagrams.

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Zusammenfassung Es wurden Liquid-Liquid-Phasendiagramme für die bin?ren Systeme Pyridin+Hexan, Pyridin+n-Heptan sowie Pyridin+n-Dodekan bestimmt. Zur Berechnung dieser Liquid-Liquid-Phasendiagramme wurde eine allgemeine quasi-chemische Theorie bezüglich von Gruppen-Oberfl?chenwechselwirkungen angewendet.

     

Excess Enthalpies of Ternary Mixtures: (2-Methyltetrahydrofuran or Di-n-Butyl ether) + 3-Methylpentane + n-Decane at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter are reported for the two ternary mixtures 2-methyltetrahydrofuran + 3-methylpentane + n-decane and di-n-butyl ether + 3-methylpentane + n-decane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.     

Theoretical study of single-electron capture in the N5+ + He and O6+ + He collisions by means of ab initio methods

Partial cross sections of single-electron capture on the n = 3 levels have been determined theoretically for the N⁵⁺ + He and O⁶⁺ + He collisions by means of a semiclassical method using ab initio potential energy curves and radial and rotational coupling matrix elements. The different behavior of these two isoelectronic systems is fairly well reproduced by our calculations.     

Density and Viscosity of Methanol + Trichloroethylene,n-Propanol + Trichloroethylene and n-Butanol + Trichloroethylene Mixtures

Abstract

Density and Viscosity measurements on the binary mixtures of methanol + trichloro-ethylene, n-propanol + trichloroethylene, and n-butanol + trichloroethylene binary mixtures at 303.15, 313.15 and 323.15K are reported. The representation of the data by simple mixing rules is also studied.     

Density, Refractive Index, and Related Properties for 2-Butanone + n-Hexane Binary Mixtures at Various Temperatures

Density refractive index n and the related properties molar volume V and molar refraction R have been investigated for 2-butanone + n-hexane liquid binary mixtures over the entire composition range and a wide range of temperatures. Some well-known relationships have been applied to study the temperature and composition dependence of the measured and derived quantities. Furthermore, the deviations of the respective excess properties V ^E, n ^E, and R ^E have been examined, with the aim of identifying particular intermolecular interaction patterns responsible for the macroscopic behavior of these binary mixtures. The results have been interpreted on the basis of structural and geometric effects between the components.     

Excess Molar Volumes of n-Pentanol + Cumene,n-Pentanol + 1,4-Dioxane and Cumene + 1,4-Dioxane at Different Temperatures

Abstract

Molar excess volumes (V^E ) and partial molar excess volumes ( ^VE ) are reported for non-electrolyte binary mixtures of n-pentanol + cumene, n-pentanol + 1,4-dioxane and cumene + 1,4-dioxane at four temperatures and over the whole concentration range. In these systems, the n-pentanol is a highly polar molecule with association in its pure state, while the others two show little polarity without association in their pure states. The results of V^E are discussed in terms of the interactions between components. The Prigogine–Flory–Patterson model of solution thermodynamics has been used to predict V^E . This work shows the importance of the three contributions δV _int, δV _p? and δV_F to V^E .     

Relative permittivities of binary mixtures of 1-butanol + n-alkane AT 298.15 k

A previous study on the physical properties of 1-alkanol + n-alkane has establised a correlation between dielectric permittivity at 1 GHz and excess molar volumes for all binary systems that were studied. In order to determine whether this behaviour is similar at lower frequencies, relative permittivity was measured at 100 kHz. The refractive index was measured to explore the effects at higher frequencies. Mixtures under study are in particular the systems (1-butanol + n-hexane, or n-octane, or n-decane) at the temperature of 298.15 K and atmospheric pressure, over the entire composition range. This revised version was published online in July 2006 with corrections to the Cover Date.     

Speeds of sound and isentropic compressibil- ities of cyclohexane+1,3-dioxolane+2-butanol and n-hexane+1,3-dioxolane+2-butanol

Speeds of sound of the ternary mixtures cyclohexane+1,3-dioxolane+2-butanol and n-hexane+1,3-dioxolane+2-butanol have been measured at the temperatures of 298.15 and 313.15 K. Isentropic compressibilities and excess isentropic compressibilities have been calculated from experimental data. We have also compared the experimental isentropic compressibilities with calculated values from the free length theory and the collision factor theory. Experimental results show positive values of excess isentropic compressibilities in almost the whole composition range for the ternary mixture containing cyclohexane, meanwhile they are negative for the mixture containing n-hexane. Such different behaviour of these systems is related to the large free volume shown by n-hexane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of Excess Molar Volumes of the Ternary Systems Containing a Propyl Alkanoate and Two Alkanes with Some Predictive Methods

Abstract

Excess molar volumes at 298.15 K of the ternary mixtures (propyl ethanoate + n-heptane + n-decane), (propyl propanoate + n-heptane + n-decane) and (propyl butanoate + n-heptane + n-decane) were determined using a DMA 60/602 Anton Paar densimeter. All the experimental values were compared with the results obtained with empirical expressions for estimating ternary properties from binary data and with the Nitta-Chao group-contribution model. For these ternary mixtures the same behaviour that had been observed in ester + n-alkane binary systems was found: excess volumes decrease when the ester length increases.     

Excess molar volumes and excess viscosities for then-hexane+dichloromethane+tetrahydrofuran ternary system at 25°C

Exces molar volumes, and excess viscosities of then-hexane+dichloromethane+tetrahydrofuran system have been determined at 25°C by measuring densities and viscosities. Different expressions exist in the literature to predict these excess properties from binary data. The empirical correlation of Cibulka is shown to be the best in this system.     

Densities, Refractive Indexes, and Excess Properties of Mixing of the n-Hexanol + Ethanenitrile + Dichloromethane Ternary System at 25°C

Excess molar volumes and excess refractive indexes of the n-hexanol + ethanenitrile + dichloromethane system and the three corresponding binary mixtures have been determined at 25°C, by measuring densities and refractive indexes. Different expressions exist in the literature to predict these excess properties from binary data. The empirical correlation of Cibulka is shown to be the best in this system. An estimation of excess molar volumes is also evaluated using a modified Heller equation, which depends on the refractive indexes of the mixtures. Comparison of the predictions by different methods with the experimental values of the physical properties has been made.     

An Ultrastable,Small {Ag7}5+ Nanocluster within a Triangular Hollow Polyoxometalate Framework

Small Ag_n nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face-centered-cubic-type small {Ag₇}⁵⁺ nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si₃W₂₇O₉₆]¹⁸⁻. The cluster showed unique {Ag₇}⁵⁺-to-POM charge transfer bands in both visible and UV light regions. Furthermore, this small {Ag₇}⁵⁺ nanocluster exhibited an unprecedented ultrastability in solution, despite having exposed Ag sites that can be accessed by small molecules, such as O₂, water, and solvents.     

Evidence for long-lived excited states of [CnH2]2+ carbodications

The energetics, structures, stabilities and reactivities of[C_nH₂]²⁺ ions have been investigated using computational methods and experimental mass spectrometric techniques. Spontaneous decompositions of [C_nH₂]²⁺ into [C_nH]⁺ + H⁺ products, observed for ions with odd-n values, have been explained by invoking the formation of excited triplet states. Even-n [C_nH]⁺ ions possess triplet ground states with low-lying excited states, whereas odd-n ions have triplet states with energies several eV above ground singlet states. Radiationless transitions of vibrationally excited long-lived triplet state ions into singlet state continua are suggested as possible mechanisms for spontaneous deprotonation processes of odd-n [C_nH₂]²⁺ ions. Evidence for these long-lived excited states has been obtained in bimolecular single electron transfer reactions.     

Densities and Viscosities of the Binary Mixtures Decanol + Some n-Alkanes at 298.15 K

Abstract

Densities and viscosities of four binary liquid systems decanol +n-heptane, +n-octane, +n-nonane, +n-decane, have been determined at 298.15 K and atomospheric pressure, over the complete composition ranges. The excess values of molar volume, viscosity and Gibbs free energy for the activation of flow were evaluated. The Grunberg-Nissan parameter was also calculated. The viscosity data were fitted to the equations of McAllister and Auslander.     

Charge exchange and charge separation processes of [C3Hn]2+ and [C3Dn]2+ (n = 1–6) dications

The charge exchange and charge separation processes of a series of [C₃H_n]²⁺ and [C₃D_n]²⁺ (n = 1–6) dications have been investigated experimentally in a mass spectrometer of reversed geometry. The relative reaction cross-sections for charge exchange with nitrogen exhibited a 20-fold variation which has implications for the interpretation of 2E spectra with respect to dication relative intensities. Charge separation resulting in deprotonation was observed for all [C₃D_n]²⁺ species investigated, while de-deuteronation was observed for [C₃D_n]²⁺ (n = 1–4) only. Intercharge separations calculated from the observed ion kinetic energies released upon charge separation suggest linear structures for [C₃D_n]²⁺ and [C₃D_n]²⁺ (n = 1–2) and cyclic structures for [C₃D_n]²⁺ (n = 3–6) and [C₃D_n]²⁺ (n = 3–4).     

Liquid Solution Densities of Ternary-Pseudobinary Mixtures of (Benzene + Cyclohexane) in the Presence of Tetrachloromethane or <Emphasis Type="Italic">n</Emphasis>-Hexane

Densities have been obtained as a function of composition for ternary-pseudobinary mixtures of [(benzene + tetrachloromethane or n-hexane) + (cyclohexane + tetrachloromethane or n-hexane)] at atmospheric pressure and the temperature 298.15 K, by means of a vibrating-tube densimeter. Excess molar volumes, V_m^E, partial molar volumes and excess partial molar volumes were calculated from the density data. The values of V_m^E have been correlated using the Redlich–Kister equation and the coefficients and standard errors were estimated. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, CCl₄ or n-C₆H₁₄, have quite different influences on the volumetric properties of binary liquid mixtures of benzene with cyclohexane.     

An Ultrastable,Small {Ag7}5+ Nanocluster within a Triangular Hollow Polyoxometalate Framework

Small Ag_n nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face‐centered‐cubic‐type small {Ag₇}⁵⁺ nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si₃W₂₇O₉₆]^18?. The cluster showed unique {Ag₇}⁵⁺‐to‐POM charge transfer bands in both visible and UV light regions. Furthermore, this small {Ag₇}⁵⁺ nanocluster exhibited an unprecedented ultrastability in solution, despite having exposed Ag sites that can be accessed by small molecules, such as O₂, water, and solvents.     

[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

We have developed a methodology for the synthesis of pyridohelicenes and their analogues based on the Ni⁰‐, Co^I‐ or Rh^I‐mediated intramolecular [2+2+2] cycloisomerisation of cyanodiynes. It allows for folding the linear precursors into the corresponding helical backbones comprising the newly formed pyridine unit in their central part. Along with racemic pyrido[n]helicenes (n=5,6,7) and their derivatives, both enantio‐ and diastereomerically pure pyrido[n]helicene‐like molecules (n=5,6) were prepared by employing the chiral substrate‐controlled cyclisation of the corresponding enantiopure cyanodiynes.