Excess Molar Volumes, Excess Viscosities and Ultrasonic Speeds of Sound of Binary Mixtures of 1,2-Dimethoxyethane with Some Aromatic Liquids at 298.15 K

Densities, viscosities and ultrasonic speeds of sound for binary mixtures of 1,2-dimethoxyethane (DME) with benzene, toluene, chlorobenzene, benzyl chloride, benzaldehyde, nitrobenzene, and aniline are reported over the entire composition range at ambient pressure and temperature (i.e., T=298.15 K and p=1.01×10⁵ Pa). These experimental data were utilized to derive the excess molar volumes (V_m^EV_{\mathrm{m}}^{\mathrm{E}}), excess viscosities (η ^E), and various acoustic parameters including the deviation in isentropic compressibility (Δκ _S ), internal pressure (π _I), and excess enthalpy (H ^E). From the excess molar volumes (V_m^EV_{\mathrm{m}}^{\mathrm{E}}), the excess partial molar volumes ([`(V)]<sub>m,1</sub><sup>E</sup>\overline{V}_{\mathrm{m},1}^{\mathrm{E}} and [`(V)]_m,2^E\overline{V}_{\mathrm{m},2}^{\mathrm{E}}) and excess partial molar volumes at infinite dilution ([`(V)]<sub>m,1</sub><sup>0,E</sup>\overline{V}_{\mathrm{m},1}^{0,\mathrm{E}} and [`(V)]_m,2^0,E\overline{V}_{\mathrm{m},2}^{0,\mathrm{E}}) were derived and discussed for each liquid component in the mixtures. The excess/deviation properties were found to be either negative or positive, depending on the molecular interactions and the nature of the liquid mixtures.     

Experimental Study of the Excess Molar Enthalpy of Ternary Mixtures Containing Water + (1,2-Propanediol, or 1,3-Propanediol, or 1,2-Butanediol, or 1,3-Butanediol, or 1,4-Butanediol, or 2,3-Butanediol)+Electrolytes at 298.15 K and Atmospheric Pressure

Excess molar enthalpies (H _m ^E) of ternary mixtures containing water+(1,2-propanediol or 1,3-propanediol or 1,2-butanediol or 1,3-butanediol or 1,4-butanediol or 2,3-butanediol)+(sodium bromide, or ammonium bromide, or tetraethyl ammonium bromide, or 1-n-butyl-3-methylimidazolium bromide at 0.1 mol⋅dm⁻³) at 298.15 K and atmospheric pressure have been determined as a function of composition using a modified 1455 Parr mixture calorimeter. The H _m ^E values are negative for all mixtures over the whole composition range. The influence of the electrolyte on the hydrophobic and hydrophilic effects as well as on the behavior of H _m ^E is discussed.     

Thermodynamic Study of Ternary Mixtures Containing 1-Methyl Pyrrolidin-2-one,Propan-2-ol and Benzene or Methyl Benzene or Cyclohexane

Densities, ρ ₁₂₃, and speeds of sound, u ₁₂₃, of 1-methyl pyrrolidin-2-one (1) + benzene or methyl benzene or cyclohexane (2) + propan-2-ol (3) ternary mixtures have been measured over the entire composition range at 308.15 K and atmospheric pressure. The resulting ρ ₁₂₃ and V₁₂₃^EV_{123}^{\mathrm{E}} data were utilized to predict excess isentropic compressibilities, (k_S^E)₁₂₃(\kappa_{S}^{\mathrm{E}})_{123}, of the studied (1+2+3) mixtures. The observed V₁₂₃^EV_{123}^{\mathrm{E}} and (k_S^E)₁₂₃(\kappa_{S}^{\mathrm{E}})_{123} data have been analyzed in terms of Graph theory (which involved the topology of a molecule). It has been observed that V₁₂₃^EV_{123}^{\mathrm{E}} and (k_S^E)₁₂₃(\kappa_{S}^{\mathrm{E}})_{123} values determined by Graph theory compare well with their corresponding experimental values.     

Thermodynamics of Ketone + Amine Mixtures Part V. Volumetric and Speed of Sound Data at (293.15, 298.15 and 303.15) K for Mixtures of 2-Heptanone with Aniline, <Emphasis Type="Italic">N</Emphasis>-Methylaniline or Pyridine

Densities, ρ, and speeds of sound, u, of 2-heptanone + aniline + N-methylaniline or + pyridine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyzer. The ρ and u values were used to calculate excess molar volumes, V ^E, and the excess functions at 298.15 K for the speed of sound, u ^E, the thermal expansion coefficient, a_p^E\alpha_{p}^{\mathrm{E}}, and for the isentropic compressibility, k_S^E\kappa_{\mathrm{S}}^{\mathrm{E}}. V ^E and k_S^E\kappa_{\mathrm{S}}^{\mathrm{E}} are both negative and increase in the sequence: aniline <N-methylaniline < pyridine. In contrast, u ^E is positive and changes in the opposite way. The data suggest the existence of interactions between unlike molecules, which are much weaker in the pyridine solution. Aromatic amine–alkanone interactions are stronger in mixtures with acetone. The linear dependence of Rao’s constant with concentration reveals that there is no complex formation in the investigated systems.     

Volumetric Properties of Acetonitrile with 1,2-Alkanediols (C2–C6) at 20°C

Dilatometric measurements of excess molar volumes, V^E and excess partial molar volumes, [`(V)] <sub>\texti</sub><sup>\textE</sup>\overline V _{\text{i}}^{\text{E}} have been made for binary mixtures of acetonitrile 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. V<sup>E</sup> for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. 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 O—H...N=C hydrogen bonding. From the experimental results, V<sup>E</sup> were calculated and correlated by Redlich–Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, [`(V)] _\texti^\textE,o\overline V _{\text{i}}^{{\text{E,o}}} .     

Investigation of the Thermodynamic Properties of the Cationic Surfactant CTAC in EG + Water Binary Mixtures

To understand the thermodynamic characteristics of cationic surfactants in binary mixtures, the aggregation behavior of hexadecyltrimethylammonium chloride (CTAC) has been investigated in ethylene glycol (EG) + water solvent mixtures at different temperatures and EG to water ratios. The critical micelle concentration (CMC) and degree of counter ion bonding (β) were calculated from electrical conductivity measurements. An equilibrium model for micelle formation was applied to obtain the thermodynamic parameters for micellization, including the standard Gibbs energies of micellization (DG_mic^o)\Delta G_{\mathrm{mic}}^{\mathrm{o}}), standard enthalpies of micelle formation (DH_mic^o)\Delta H_{\mathrm{mic}}^{\mathrm{o}}) and standard entropies of micellization (DS_mic^o)\Delta S_{\mathrm{mic}}^{\mathrm{o}}). Our results show that DG_mic^o\Delta G_{\mathrm{mic}}^{\mathrm{o}} is always negative and slightly dependent on temperature. The process of micellization is entropy driven in pure water, whereas in EG + water mixtures the micellization is enthalpy driven.     

Thermodynamic Investigation of Molecular Interactions in 1,3-Dioxolane or 1,4-Dioxane+Benzene or Toluene+Formamide or +<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide Ternary Mixtures at 308.15 K and Atmospheric Pressure

Excess molar volumes, V^E₁₂₃V^{\mathrm{E}}_{123} of 1,3-dioxolane or 1,4-dioxane (1) + benzene or toluene (2) + formamide or + N,N-dimethylformamide (3) ternary mixtures at 308.15 K and at atmospheric pressure have been determined dilatometrically over the entire composition range. The excess molar volumes data of these ternary systems were fitted to the Redlich–Kister equation. The data have been analyzed in terms of Graph theory (model) to understand the nature and strength of molecular interactions existing in these mixtures. It has been observed that V^E₁₂₃V^{\mathrm{E}}_{123} values predicted by Graph theory compare well with their corresponding experimental values.     

Thermochemistry of 2-Aminopyridine (C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>)(s)

The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory, the molar enthalpy of solution of the title compound at infinite dilution was calculated to be D_solH_m^￥ = 14.34 kJ·mol^-1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters b_MX^(0)L, b_MX^(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and C_MX^fLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies ( ^φ L) and relative partial molar enthalpies of the compound ([`(L)]₂)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the cation C₅H₇N₂ ⁺\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be D_fH_m^o(C₅H₇N₂⁺,aq)=-(2.096±0.801) kJ·mol^-1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}.     

Densities and Excess Molar Volumes of Binary and Ternary Mixtures Containing Acetonitrile + Acetophenone + 1,2-Pentanediol: Experimental Data,Correlation and Prediction by PFP Theory and ERAS Model

Densities were determined experimentally over the entire range of composition at 298.15 K for the ternary system acetonitrile (1) + acetophenone (2) + 1,2-pentanediol (3) and for the three corresponding binary systems. Excess molar volumes were calculated for the binary and the ternary systems. These results were fitted to variable-degree polynomials. Further, the Prigogine-Flory-Patterson (PFP) theory and Extended Real Associated Solution (ERAS) model were applied to V_m^EV_{m}^{\mathrm{E}} for the binary mixtures of acetonitrile + acetophenone, acetonitrile + 1,2-pentanediol and acetophenone + 1,2-pentanediol, and the findings compared with the experimental results.     

Topological and Thermodynamic Studies for Binary Mixtures of 1,4-Dioxane with Anilines at 308.15 K

Excess molar volumes, V ^E, excess molar enthalpies, H ^E, speeds of sound, u, and vapor-liquid equilibrium data of 1,4-dioxane (1) + aniline or N-methyl aniline or o-toluidine (2) binary mixtures have been measured as a function of composition at 308.15 K. Isentropic compressibility changes that occur for mixing, k_S^E\kappa_{S}^{\mathrm{E}}, and excess Gibb’s energies, G ^E, have been determined by employing speeds of sound and vapor-liquid equilibrium data. The V^E, H^E,k_S^EV^{\mathrm{E}}, H^{\mathrm{E}},\kappa_{S}^{\mathrm{E}} and G ^E values have been estimated by (i) graph theory and (ii) the Prigonone-Flory-Patterson theory (PFP). It was observed that values of V^E, H^E,k_S^EV^{\mathrm{E}}, H^{\mathrm{E}},\kappa_{S}^{\mathrm{E}} and G ^E predicted by graph theory compare well, relative to the PFP theory, with their corresponding experimental values.     

Topological and Thermodynamic Investigations of Ternary Mixtures Containing Cyclic Ethers: Excess Molar Volumes

Excess molar volumes, V₁₂₃^EV_{123}^{\mathrm{E}}, of 1,3-dioxolane or 1,4-dioxane (1) + aniline (2) + benzene or toluene (3) ternary mixtures have been determined over the entire mole fraction range at 308.15 K. V₁₂₃^EV_{123}^{\mathrm{E}} data have been fitted to the Redlich-Kister equation to evaluate ternary adjustable parameters and standard deviations. The observed V₁₂₃^EV_{123}^{\mathrm{E}} data have been analyzed in terms of (i) Graph theory, (ii) Prigogine-Flory-Patterson theory, and (iii) Sanchez and Lacombe theory. It has been observed that V₁₂₃^EV_{123}^{\mathrm{E}} values predicted by Graph theory compare well with the corresponding experimental values.     

Ultrasound Speeds and Molar Isentropic Compressions of Aqueous 2-(Ethylamino)ethanol Mixtures from 283.15 to 303.15 K

Ultrasound speeds in 31 aqueous binary mixtures of 2-(ethylamino)ethanol (EEA) were experimentally determined over the entire composition range at 283.15, 288.15 and 303.15 K. Isentropic compressibilities, κ _S , were calculated by combining the ultrasound speed with density data. Excess molar isentropic compressions, K_S,m^EK_{S,\mathrm{m}}^{\mathrm{E}}, referred to a thermodynamically-defined ideal liquid mixture, were estimated. Excess partial molar isentropic compressions, K_S,i^EK_{S,i}^{\mathrm{E}}, of both components and their respective limits at infinite dilution, K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty}, were analytically obtained using Redlich-Kister type equations. The temperature and composition dependences of K_S,i^EK_{S,i}^{\mathrm{E}} were analyzed, especially in the water and EEA rich regions. The present K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty} values are compared with those for water + 2-diethylaminoethanol (DEEA) and water + diethylamine (DEA) mixtures, as a function of temperature. Although the K_S,2^E,￥K_{S,2}^{\mathrm{E,}\infty} values for EEA and DEEA increase with temperature, the opposite trend is observed for DEA. Results for aqueous EEA and aqueous DEEA seem to support the idea that the driving force for hydrophobic hydration relies on solute-solvent hydrophilic interaction rather than on enhancing the water structure. On the other hand, different temperature dependent behavior is observed for the differential volumetric properties K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty} and limiting excess partial molar isobaric expansion, E_P,i^E,￥E_{P,i}^{\mathrm{E,}\infty}, which are attributed to the different sensitivity of these properties to hydration.     

Measurements of the Molar Heat Capacities and Excess Molar Heat Capacities for Water + Organic Solvents Mixtures at 288.15 K to 303.15 K and Atmospheric Pressure

Experimental molar heat capacity data (Cp _m) and excess molar heat capacity data (Cp^E_m\mathit{Cp}^{\mathrm{E}}_{\mathrm{m}}) of binary mixtures containing water + (formamide or N,N-dimethylformamide or dimethylsulfoxide or N,N-dimethylacetamide or 1,4-dioxane) at several compositions, in the temperature range 288.15 K to 303.15 K and atmospheric pressure, have been determined using a modified 1455 PAAR solution calorimeter. The excess heat capacities are positive for aqueous solutions containing 1,4-dioxane, N,N-dimethylformamide or dimethylsulfoxide, negative for solutions containing water + formamide and show a sigmoid behavior for mixtures containing water + N,N-dimethylacetamide, over the whole composition range. The experimental excess molar heat capacities are discussed in terms of the influence of temperature and of the organic solvent type present in the binary aqueous mixtures, as well as in terms of the existing molecular interactions and the organic solvent’s molecular size and structure.     

Kinetic Study of the Oxidation of N,N-Dimethylethanolamine by Bis(Hydrogenperiodato)Argentate(III) in Aqueous Solution

The oxidation of N,N-dimethylethanolamine (DMEA) by bis(hydrogenperiodato) argentate(III) ([Ag(HIO₆)₂]⁵⁻) was studied in aqueous alkaline medium. Formaldehyde and dimethylamine were identified as the major oxidation products after the oxidation of DMEA. The oxidation kinetics was followed spectrophotometrically in the temperature range of 25.0 °C–40.0 °C. It was found that the reaction was first order in [Ag(III)]; the oberved first-order rate constants k _obsd as functions of [DMEA], [OH⁻] and total concentration of periodate ([IO₄^-]_tot[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}) were analyzed and were revealed to follow a rate expression: k_obsd = (k₁ +k₂[OH^-])K₁K₂[DMEA]/{f([OH^-])[IO₄^-]_tot+ K₁ + K₁K₂[DMEA]}k_{\mathrm{obsd}} = (k_{1} +k_{2}[\mathrm{OH}^{-}])K_{1}K_{2}[\mathrm{DMEA}]/\{f([\mathrm{OH}^{-}])[\mathrm{IO}_{4}^{-}]_{\mathrm{tot}}+ K_{1} + K_{1}K_{2}[\mathrm{DMEA}]\}. Rate constants k ₁ and k ₂ and equilibrium constant K ₂ were derived; activation parameters corresponding to k ₁ and k ₂ were computed. In the proposed reaction mechanism, a peridato-Ag(III)-DMEA ternary complex is formed indirectly through a reactive intermediate species [Ag(HIO₆)(OH)(H₂O)]²⁻. In subsequent rate-determining steps as described by k ₁ and k ₂, the ternary complex decays to Ag(I) through two reaction pathways: one of which is spontaneous and the other is prompted by an OH⁻.     

Complexation of 4′-Nitrobenzo-15-crown-5 with Zn<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript>, Cr<Superscript>3+</Superscript> and Sn<Superscript>4+</Superscript> Cations in Acetonitrile–Ethanol Binary Mixtures

The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn²⁺, Mn²⁺, Cr³⁺ and Sn⁴⁺ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH (mol-%AN=76) binary solvent at 298.15 K is: Cr³⁺>Mn²⁺≈Zn²⁺>Sn⁴⁺, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between the stability constants (log ₁₀ K _f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DH_c^o, DS_c^o)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Apparent Molar Volume and Isentropic Compressibility for the Binary Systems {Methyltrioctylammonium Bis(trifluoromethylsulfonyl)imide + Methyl Acetate or Methanol} and (Methanol + Methyl Acetate) at <Emphasis Type="Italic">T</Emphasis>=298.15, 303.15, 308.15 and 313.15 K and Atmospheric Pressure

The densities and speeds of sound for binary mixtures containing the solute ionic liquid (IL) methyltrioctylammonium bis(trifluoromethylsulfonyl)imide ([MOA]⁺[Tf₂N]⁻), solute/solvent methanol, and solvent methyl acetate have been measured at 298.15, 303.15, 308.15 and 313.15 K at atmospheric pressure. The binary mixtures studied are ([MOA]⁺[Tf₂N]⁻ + methyl acetate or methanol), and (methanol + methyl acetate). The apparent molar volume, V _φ and the apparent molar isentropic compressibility, k _φ , have been evaluated from the experimental density and speed of sound data, respectively. The parameters of a Redlich–Mayer type equation were fitted to the apparent molar volume and apparent molar isentropic compressibility data. The apparent molar volume and apparent molar isentropic compressibility at infinite dilution, V_f⁰V_{\phi}^{0} and k_f⁰k_{\phi}^{0}, respectively, of the binary solutions have also been calculated at each temperature. The infinite dilution apparent molar volume indicates that intermolecular interactions for (IL + methyl acetate) mixtures are stronger than for (IL + methanol) mixtures at all temperatures except at 298.15 K, and that V_f⁰V_{\phi}^{0} for the (IL + methyl acetate or methanol) binary systems increases with an increase in temperature. For the (methanol + methyl acetate) system the intermolecular interaction are weaker and V_f⁰V_{\phi}^{0} also increases with an increase in temperature. Values of the infinite dilution apparent molar expansibility, E_f⁰E_{\phi}^{0}, indicate that the interaction between (IL + methyl acetate) is greater than for (IL + methanol) and (methanol + methyl acetate).     

Solution Thermodynamics of Ethylhexyl Triazone in Some Ethanol + Ethyl Acetate Mixtures

Ethylhexyl triazone (EHT) is a sunscreen agent that is widely used in skin care product formulations, whose physicochemical properties have not been previously studied in detail. For this reason, solubility data were measured for EHT in ethanol (EtOH) + ethyl acetate (AcOEt) mixtures at five temperatures. By using the van’t Hoff and Gibbs equations, the thermodynamic functions: Gibbs energy, enthalpy, and entropy of solution, and of mixing, were evaluated from these solubilities. The solubility is greatest in mixtures with 0.10 and 0.20 mass fraction EtOH, but decrease as the EtOH mass fraction increases in the solvent mixtures. By means of an enthalpy-entropy compensation analysis, a nonlinear DH_soln⁰\Delta H_{\mathrm{soln}}^{0} versus DG_soln⁰\Delta G_{\mathrm{soln}}^{0} compensation plot was obtained having both negative and positive slopes as the solvent composition was varied. Accordingly to these results, it follows that the driving function for solubility of EHT is the entropy for solutions rich in EtOH or AcOEt, whereas in mixtures of medium composition, the driving function is the enthalpy.     

Acoustic,Viscometric, and Spectroscopic Studies of Dipropylene Glycol Monopropyl Ether with <Emphasis Type="Italic">n</Emphasis>-Alkanols at Temperatures of 288.15, 298.15, and 308.15 K

Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol, and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds of sound were combined with our previous densitity results to obtain the isentropic compressibility κ _S . The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K _S,m and its excess counterparts K_S,m^EK_{S,m}^{\mathrm{E}}. The K_S,m^EK_{S,m}^{\mathrm{E}} values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑x _i ln η _i and excess Gibbs energies of activation for viscous flow ΔG ^∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities [`(K)]_f,i⁰\overline{K}_{\phi ,i}^{0} of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental results have also been discussed on the basis of IR measurements.     

Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol by bis(hydrogen periodato)argentate(III) complex anion: a kinetic study

Oxidation of 3-(4-methoxyphenoxy)-1,2-propanediol (MPPD) by bis(hydrogenperiodato) argentate(III) complex anion, [Ag(HIO₆)₂]⁵⁻ has been studied in aqueous alkaline medium by use of conventional spectrophotometry. The major oxidation product of MPPD has been identified as 3-(4-methoxyphenoxy)-2-ketone-1-propanol by mass spectrometry. The reaction shows overall second-order kinetics, being first-order in both [Ag(III)] and [MPPD]. The effects of [OH⁻] and periodate concentration on the observed second-order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced:

The Enthalpy of Solution of the Alanine-Based Ionic Liquid [C<Subscript>4</Subscript>mim][Ala]

The molar enthalpies of solution of an alanine-based ionic liquid (IL) [C₄mim][Ala], 1-butyl-3-methylimidazolium alanine, containing various amount of water and various molalities Δ_sol H _m(wc), were measured with a solution-reaction isoperibol calorimeter at (298.15±0.01) K, where wc denotes water content. According to Archer’s method, the standard molar enthalpies of solution of [C₄mim][Ala] containing known amounts of water, D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) , were obtained. In order to eliminate the effect of the small amount of residual water in the source [C₄mim][Ala], a linear fitting of D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) against water content was carried out, yielding a good straight line where the intercept is the standard molar enthalpy of solution of anhydrous [C₄mim][Ala], D_solH_m^o(pure IL)=-(61.42±0.08)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{pure}\ \mathrm{IL})=-(61.42\pm 0.08) kJ⋅mol⁻¹. The hydration enthalpy of the alanine anion [Ala]⁻ was estimated using Glasser’s lattice energy theory.