Speeds of sound and isentropic compressibilities of binary mixtures containing trialkylamines with alkanes and mono-alkylamines at 303.15 and 313.15 K

Isentropic compressibilities κ_S, and excess isentropic compressibilities κ_S^E have been determined from measurements of speeds of sound u and densities ρ of 14 binary mixtures of triethylamine (TEA) and tri-n-butylamine (TBA) with n-hexane, n-octane, iso-octane, n-propylamine, n-butylamine, n-hexylamine and n-octylamine. The relative magnitude and sign of κ_S^E have been interpreted in terms of molecular interactions and interstitial accommodation. The values of κ_S^E for TEA + alkane are positive while for TBA + alkane are negative. The values of κ_S^E for TEA + primary amine become progressively less positive and eventually to negative with the increase in chain length of alkylamine. In case of TBA + primary amine, the values of κ_S^E increase from n-propylamine to n-butylamine, and then decrease with chain length of primary amine. The experimental speeds of sound u have been analyzed in terms of collision factor theory, free length theory and Prigogine–Flory–Patterson statistical theory of solutions.     

Excess volumes for n-alkanols + n-alkanes I. Binary mixtures of methanol,ethanol, n-propanol,and n-butanol + n-heptane

Excess volumes V^E measured at 298.15 K in a successive-dilution dilatometer are reported for binary mixtures of the n-alkanols C₁ to C₄ + n-heptane. For ethanol +, and n-butanol + n-heptane, the measurements were extended to high dilutions of alkanol. V^E is positive for all of the mixtures but decreases rapidly in magnitude for increasing chain length of the n-alkanol. The results were used to estimate the excess partial molar volumes of the components.     

An effective modification of the Benedict–Webb–Rubin equation of state

A modification of the BWR equation of state is proposed, which is a simplified form of a previously proposed one. It applies to systems formed by hydrocarbons and related compounds, with particular attention to the critical conditions. The range of treatable compounds was extended to a value 0.9 of the acentric factor, corresponding to C₂₀ hydrocarbons. The critical compressibility factor Z_c was made independent of the acentric factor, for a more accurate prediction of pure-component properties (the previous equation did not give the same improvement). Mixing rules require one binary interaction constant for each component pair. Zero binary constants can be used for methane–alkane and alkane–alkane pairs. Examples of applications to pure hydrocarbons and their mixtures are given.     

Studies of viscosity and excess molar volume of binary mixtures: 4. 1-Alkanol + tri-n-butylamine mixtures at 303.15 and 313.15 K

The excess molar volume V^E, the viscosity deviation Δη and the excess Gibbs energy of activation ΔG^1E of viscous flow are calculated from density and viscosity measurements of six mixtures of 1-propanol, 1-butanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol with tri-n-butylamine over the entire range of mole fractions at 303.15 and 313.15 K. The values of V^E of all six systems are very large and negative. Except for 1-propanol+tri-n-butylamine, the magnitude of negative deviations in viscosity increases with chain length of alkanol. The results have been explained considering mixed associated species of type A_iB involving alkanol (A) with tri-n-butylamine (B) through OH⋯N bonds. The viscosity data have been correlated with the equations of Grunberg and Nissan, Tamura and Kurata, Hind, McLaughlin and Ubbelohde, Katti and Chaudhri, McAllister, Heric, and of Auslaender.     

Viscosity of Aqueous Solutions of n-butylamine,sec-butylamine and tert-butylamine

Abstract

Viscosities of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA) and W + tert-butylamine (TBA) have been measured in the temperature range 298.15–323.15K. The viscosities (η) and excess viscosities (η^E) have been plotted against mole fraction of amines (X ₂). On addition of amines to water, viscosities first increase rapidly, then pass through maxima at 0.2 mole fraction of amines and then decline continuously as the addition of amines is continued. η^E show large positive values, with maxima also at 0.2 mole fraction of amines. The maxima of the curves of η and η^E vs. mole fraction of butylamines follow the order, W + TBA > W + SBA > W + NBA. The ascending part of the η vs. X ₂ curves in the water-rich region is explained by the hydrophobic hydration caused by the hydrocarbon tails and the hydrophilic effect due to — NH₂ group of amines. Following the maxima, amine - amine association is preferred, which accounts for the steady decrease of viscosity up to the pure state of amines.     

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. II. Polymerization of acrylonitrile by ceric ion in presence of various substituted amines

The effect of various substituted amines on the polymerization of acrylonitrile initiated by ceric ammonium sulfate has been studied in aqueous solution at 30°C. It was found that the secondary and tertiary amines considerably increased the rate of polymerization, whereas the primary amines seemed to have no effect at all. From the kinetic studies it was found that the overall polymerization rate R_p is independent of ceric ion concentration and can be expressed by the equation: R_p = k₁ [amine] [monomer] + k₂[monomer]², where k₁ and k₂ are constants (involving different rate constants). The accelerating effect of the amines was attributed to a redox reaction between the ceric ion and the amine involving a single electron transfer, the relative activity of the different amines being thus dependent on the relative electron-donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.     

Excess Molar Volumes for Binary Mixtures of 1-Alkanol and 1-Alkene. II. The System 1-Alkanol + 1-Octene at 15 and 35°C

Excess molar volumes V ^E measured at 15 and 35°C for the (1-propanol + 1-octene), (1-butanol + 1-octene), (1-octanol + 1-octene), and (1-decanol + 1-decene) systems are reported. These data and the measurements reported before at 25°C for this series of mixtures were used to calculate the excess molar isobaric thermal expansion A _p ^E = ( V ^E/ T)_p at 25°C. In the above series of mixtures the A _p ^E values change from positive over the whole concentration range in the systems formed by 1-propanol and 1-butanol, to positive-negative for longer chain alkanols, the positive values occurring in the alkene-rich region. For systems characterized by the sigmoid shape, the positive region of A _p ^E values decreases with increasing length of the 1-alkanol molecule. The modified model of associated mixtures proposed by Treszczanowicz and Benson predicts qualitatively the changes in the shape of the A _p ^E curves. The model allows interpretation of the above results as a balance between the contributions due to self-association of alkanol, nonspecific interactions, and free volume.     

Kinetic Study of the Alkaline Hydrolysis of 1,n‐Bis(4‐cyanopyridinium)alkanes: Charge Density and New Conformational Effects on the Reactivity of 1,3‐Bis(4‐cyanopyridinium)propane

The alkaline hydrolysis reaction rates of 1,n‐bis(4‐cyanopyridinium)alkane derivatives C_nbis(CP)²⁺ with n = 3, 6, and 8 were studied and compared to the reaction rate of the N‐methyl‐4‐cyanopyridinium (MCP⁺). C₆bis(CP)²⁺ and C₈bis(CP)²⁺ obeyed the first‐order kinetic law. However for C₃bis(CP)²⁺ data fitted to a consecutive two‐step model reaction, the observed rate constants (k_obs) of C₈bis(CP)²⁺ and C₆bis(CP)²⁺ are approximately 50% and 100%, respectively, higher than those for MCP⁺, an effect mainly assigned to the higher charge density of these two derivatives. For C₃bis(CP)²⁺, the k_obs of the second (slow) step is almost twofold the value observed for C₆bis(CP)²⁺, whereas the first (fast) step is approximately six times higher. As for MCP, the hydrolysis of C_nbis(CP)²⁺ generates pyridone (P^o) and carbamidopyridinium (A⁺) units. For C₃bis(CP)²⁺, however at pHs above 11.5, one additional product is formed. From the existence of the new product and the kinetic evidence, a “sandwiched‐type” complex with the OH^? inserted between the rings is proposed. This structural effect in the C₃bis(CP)²⁺ due to the conformational effect justifies the (i) two kinetic steps, (ii) high rate constants, (iii) high P^o/A⁺ ratios, (iv) observed temperature and salt effects, and (v) the formation of the new product.     

Thermodynamics of molecular interactions in ethyl iodide+toluene mixtures

The excess Gibb's free energy of mixing, G^E, for ethyl iodide+toluene at 25°C have been obtained from the measured vapor pressuure data. The H^E and G^E values for ethyl iodide+toluene are positive throughout the ethyl iodide concentration range and G^E>H^E. The results have been analyzed in terms of Flory and ideal associated model theory of nonelectrolyte solutions. It has been observed that the ideal associated model approach which assumes the presence of AN and A₂B molecular species describes well (within±10 J-mol^–1 in the worst case) the general dependence of H^E on X_A (mole fraction of ethyl iodide) over the whole composition range for ethyl iodide+toluene mixtures. The equilibrium constants for A+A AB and 2A+BA₂B reactions along with the enthalpies of formation of AB and A₂B molecular species have been calculated.     

Application of the Perturbed-Chain SAFT equation of state to polar systems

The Perturbed-Chain SAFT (PC-SAFT) equation of state is applied to pure polar substances as well as to vapor–liquid and liquid–liquid equilibria of binary mixtures containing polar low-molecular substances and polar co-polymers. For these components, the polar version of the PC-SAFT model requires four pure-component parameters as well as the functional-group dipole moment. For each binary system, only one temperature-independent binary interaction k_ij is needed. Simple mixing and combining rules are adopted for mixtures with more than one polar component without using an additional binary interaction parameter. The ability of the model to accurately describe azeotropic and non-azeotropic vapor–liquid equilibria at low and at high pressures, as well as liquid–liquid equilibria is demonstrated for various systems containing polar components. Solvent systems like acetone–alkane mixtures and co-polymer systems like poly(ethylene-co-vinyl acetate)/solvent are discussed. The results for the low-molecular systems also show the predictive capabilities of the extended PC-SAFT model.     

Studies on some radical transfer reactions by entrapping the radicals as polymer end groups. I. Reaction of hydroxyl radicals with amines

The reaction of OH radicals with a number of amines has been studied by entrapping the resultant radicals as polymer end groups which have been detected and estimated by the sensitive dye partition technique. Expressions have been developed relating the average amounts of end groups per polymer molecule to the rate constant of the radical transfer reaction, the rate constants determined for reaction with n-butyl, n-hexyl, and n-octyl amine being 1.00 × 10¹⁰, 1.31 × 10¹⁰, and 1.46 × 10¹⁰ mol^?1 L s^?1, respectively, at 25°C. The order of reactivity for amines of different classes has been found to be as primary < secondary > tertiary, the rate constants for reaction with n-butyl, dibutyl, and tributyl amine being 1.00 × 10¹⁰, 1.81 × 10¹⁰, and 1.67 × 10¹⁰ mol^?1 L s^?1, respectively, at 25°C. The change in the reactivity of the amine with chain length and amine class has been explained by activation and deactivation of the CH₂ group from which H abstraction by OH radicals occurs, respectively, by the alkyl group and by the protonated amino nitrogen under the acidic condition of the medium. Between pH 1.00 and 2.17, the rate of the reaction with n-butyl amine remains practically unchanged, but from pH 2.20 to 2.72 the rate constant increases with increasing pH, indicating that deprotonation of the positively charged nitrogen starts at about pH 2.20. The method is simple and accurate and can be applied to detect and estimate very reactive radicals.     

Phase-equilibrium calculations for n-alkane + alkanol systems using continuous thermodynamics

A new association model based on continuous thermodynamics is introduced and applied to six systems of the type n-alkane (n-hexane, n-heptane, n-octane) + alkanol (methanol, ethanol). The alkanol is considered to be a mixture of chain associates with the composition described by a continuous distribution function. This distribution function is derived as an analytical expression from the mass action law applied to the association equilibrium. To consider the entropic contribution originating from the size differences of the molecules (associates) activity coefficients based on Flory–Huggins model are included in the mass action law. Unlike the molecular-mass distribution of a polymer the chain-length distribution of the associates depends on the temperature and on the mole fraction of the alkanol. The treatment of vapor–liquid equilibrium and liquid–liquid equilibrium is similar to that of an oil system or of a polymer solution using continuous thermodynamics. Different to other chemical models of association there is no additive split into a physical and a chemical contribution. The equilibrium constants of association were fitted to vapor-pressure data of methanol and ethanol. The model needs only one interaction parameter being independent of temperature and taking the same value for all systems studied. Considering the simplicity of the model, both the liquid–liquid equilibrium of the three methanol systems and the vapor–liquid equilibrium of all six systems are predicted with reasonable accuracy.     

Quenching of O2(1Δg) by aliphatic amines

The quenching rate constants of O₂(¹Δ_g) with n-butylamine, diethylamine, dipropylamine, dibutylamine, and tripropylamine have been determined in a discharge flow system. The rate constants are found to be (1.6 ± 0.2) × 10³, (8.5 ± 0.6) × 10⁴, (9.8 ± 0.5) × 10⁴, (2.1 ± 0.1) × 10⁵, and (8.6 ± 0.5) × 10⁵ 1 mol^?1 s^?1, respectively. The rate constants are found to increase in the order, tertiary amine → secondary amine → primary amine. The “inductive effect” of alkyl substitution is also found to increase the rate constant in a given series of amines.     

Kinetic study of CO2 absorption in aqueous solutions of 2-((2-aminoethyl)amino)-ethanol using a stirred cell reaction calorimeter

In the literature, aqueous 2-((2-aminoethyl)amino) ethanol (AEEA) is identified as a promising solvent for postcombustion CO₂ capture. In this work, the kinetics of CO₂ absorption in the aqueous AEEA, containing a primary and a secondary amino group, is studied over a wide temperature range of 303.15-343.15 K and the amine concentration in the range of 0.47-2.89 M using the fall-in-pressure technique in a stirred cell reaction calorimeter setup with a horizontal gas-liquid interface. The overall rate constants for (AEEA + H₂O + CO₂) reaction system are estimated in the pseudo–first-order reaction regime. The kinetic models based on zwitterion and the termolecular reaction mechanisms are used to predict kinetic rate constants. The experimental kinetic data are better correlated using the zwitterion mechanism (AAD 9.18%) than that of the termolecular mechanism (AAD 10.4%). The density, viscosity, and physical solubility of pure components and aqueous binary mixtures of AEEA are also measured at the similar temperature and concentration ranges of rate kinetics. Empirical models are proposed to predict pure component density and viscosity data with AAD of 0.02% and 7.17%, respectively. The Redlich-Kister model, the Grunberg-Nissan model, and the O'Connell's model are used to correlate experimental density, viscosity, and physical solubility data of the binary mixtures with AAD of 0.034%, 4.92%, and 6.5%, respectively. The reaction activation energy (E_a ∼ 32 kJ/mol) of the (AEEA + H₂O + CO₂) system is calculated from the Arrhenius power-law model using the zwitterion mechanism, which indicates lower energy barrier than that of the reported value for monoethanolamine (∼44 kJ/mol) in the literature.     

Calorimetric effects of short-range orientational order in solutions of benzene or n-alkylbenzenes in n-alkanes

A Picker flow microcalorimeter was used to determine molar excess heat capacities, C^E_p, at 298.15 K, as function of concentration, for the eleven liquid mixtures: benzene+n-tetradecane; toluene+n-heptane, and +n-tetradecane; ethylbenzene+n-heptane, +n-decane, +n-dodecane; and +n-tetradecane; n-propylbenzene +n-heptane, and +n-tetradecane; n-butylbenzene+n-heptane, and +n-tetradecane. In addition, molar excess volumes, V^E, at 298.15 K, were obtained for each of these systems (except benzene+n-tetradecane) and for toluene+n-hexane. The excess volumes which are generally negative with a short alkane, increase and become positive with increasing chain length of the alkane. The excess heat capacities are negative in all cases. The absolute ¦C^E_p¦ increased with increasing chain length of the n-alkane. A formal interchange parameter, C_p12, is calculated and its dependence on n-alkane chain length is discussed in terms of molecular orientations.     

Concentration Effects in Sec for Polymer/Polymer/Solvent Systems

Abstract

A model quantitatively describing the experimental shifts in elution volumes of polymeric solute A in the presence of another polymer B is developed. The concentration-dependent shrinkage of A coils has been evaluated from the intrinsic viscosity displayed by polymer A in the ternary solution formed by itself at c_A concentration + polymer B at c_B concentration + solvent. Resulting concentration effects depend on both polymer concentrations (c_A and c_B), on the intrinsic viscosities of both polymers in the solvent (|η|A and |η|B), on the Huggins' coefficients k_A and k_B, and on the quadratic concentration coefficients in the polynomial expansion of ηsp/c, namely k^′ _A and k^′ _B. Predicted elution volumes are compared with experimental ones for two different types of literature systems: those studying polymer A elution at diverse c_A concentrations in eluents consisting of mixtures of polymer B + solvent and those in which polymer A + polymer B mixtures are injected at once in the pure solvent used as eluent. In order to eliminate experimental uncertainties about k_i and k^′ _i (i=A, B) values, applied k^′ _i values were those obtained from the empirical correlation k^′ _i + 0.122 = k_i ² whereas k_i ones were obtained from Imai's equation.     

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 .     

Thermodynamics of mixtures containing a very strongly polar compound: IV – application of the DISQUAC,UNIFAC and ERAS models to DMSO+ organic solvent systems

Binary mixtures of dimethylsulfoxide (DMSO) with alkane, benzene, toluene 1-alkanol, or 1-alkyne have been investigated in terms of DISQUAC. The corresponding interaction parameters are reported. ERAS parameters for 1-alkanol + DMSO mixtures are also given. ERAS calculations were developed considering DMSO as a not self-associated compound.

DISQUAC represents fairly well a complete set of thermodynamic properties: molar excess enthalpies, molar excess Gibbs energies, vapor–liquid equilibria, natural logarithms of activity coefficients at infinite dilution, or partial molar excess enthalpies at infinite dilution. DISQUAC improves UNIFAC calculations for H ^E . Both models yield similar results for VLE. In addition, DISQUAC also improves, ERAS results for 1-alkanol + DMSO mixtures. This may be due to ERAS cannot represent the strong dipole–dipole interactions present in such solutions.