Study of an Alcohol’s Influence on the CMC and Thermodynamic Functions of Anionic Surfactants in DMA/Long-chain Alcohol Solutions Using a Microcalorimetric Method

The power-time curves for the micelle formation process were determined for two anionic surfactants, sodium laurate (SLA) and sodium dodecyl sulfate (SDS), in mixed alcohol + N,N-dimethylacetamide (DMA) solvent using titration microcalorimetry. From the data of the lowest point and the area of the power-time curves, their critical micelle concentration (CMC) and ΔH _m^o were obtained. The other thermodynamic functions of the micellization process (ΔG _m^o and ΔS _m^o) were also calculated with thermodynamic equations. For both surfactants, the effects of the carbon number (chain length) of the alcohol, the concentration of alcohol, and the temperature on the CMC and thermodynamic functions are discussed. For systems containing identical concentrations of a different alcohol, values of the CMC, ΔH _m^o and ΔS _m^o increased whereas ΔG _m^o decreased with increasing temperature. For systems containing an identical alcohol concentration at the same temperature, values of the CMC, ΔH _m^o,ΔG _m^o and ΔS _m^o decrease with increasing carbon number of alcohol. For systems containing the same alcohol at the same temperature, the CMC and ΔG _m^o values increase whereas ΔH _m^o and ΔS _m^o decrease with increasing alcohol concentration.     

微量量热法研究阴离子表面活性剂在DMA/长链醇体系中CMC和热力学函数

在N,N-二甲基乙酰胺(DMA)/长链醇非水溶液体系中, 利用微量量热仪, 研究阴离子表面活性剂十二烷基羧酸钠(SLA)、十二烷基硫酸钠(SDS)的临界胶束浓度(CMC)和热力学函数. 本文在十二烷基羧酸钠, 十二烷基硫酸钠的N,N-二甲基乙酰胺溶液中, 分别加入长链醇(庚醇、辛醇、壬醇、癸醇), 测定体系的热功率-时间曲线. 借助热力学理论, 由测得曲线, 进一步得到临界胶束浓度和热力学函数(ΔH_m⁰, ΔG_m⁰和ΔS_m⁰). 讨论了温度、醇的碳原子数目、醇的浓度与热力学参数之间的关系. 结果表明, 对十二烷基羧酸钠或十二烷基硫酸钠的DMA溶液, 在含有相同浓度的各种醇的体系中, CMC, ΔH_m⁰和ΔS_m⁰的值随着温度的升高而增加, 而ΔG_m⁰的值随着温度的升高而降低. 在相同温度及相同浓度的醇体系中, CMC, ΔH_m⁰,ΔG_m⁰和ΔS_m⁰的值都随着醇中碳原子数目的增加而降低. 在相同温度及相同醇的体系中, CMC, ΔG_m⁰的值随着醇的浓度的增加而增大, 而ΔH_m⁰, ΔS_m⁰的值随着醇的浓度的增加而减少.     

Studies on the CMC and Thermodynamic Functions of a Cationic Surfactant in DMF/Long-Chain Alcohol Systems Using a Microcalorimetric Method

The power-time curves of the micelle formation process were determined at four temperatures for a cationic surfactant [cetyltrimethylammonium bromide (CTAB)] in a non-aqueous solvent [N,N-dimethylformamide (DMF)] by titration microcalorimetry. From the data of the minimum of the titration point and the area of the power-time curves, values of their CMC and ΔH _m ^θ were obtained. Values of ΔG _m ^θ and ΔS _m ^θ were also calculated according to standard thermodynamic relations. For the cationic surfactant CTAB, the relationships involving the carbon numbers of the alcohols, the alcohol’s concentration, and the temperature on the CMC, and also the thermodynamic functions for micellization are discussed. For systems containing an identical concentration of various alcohols, values of the CMC, ΔH _m ^θ and ΔS _m ^θ increased whereas those of ΔG _m ^θ decreased with increasing temperature. For systems containing identical alcohol concentrations at the same constant temperature, values of the CMC, ΔH _m ^θ ,ΔG _m ^θ and ΔS _m ^θ decreased with increasing carbon number of the alcohol. For systems containing the same alcohol at the same temperature, the CMC and ΔG _m ^θ values increased whereas ΔH _m ^θ and ΔS _m ^θ decreased with increasing alcohol concentration.     

Studies on Thermodynamics of Micellization and Solvophobic Interactions of Novel Surfactant–Cr(III) Complexes in Non-aqueous Solvents

The critical micelle concentration (CMC) of surfactant–Cr(III)–dodecylamine complexes of the type cis-α-[Cr(trien)(C₁₂H₂₅NH₂)X]²⁺ (where trien = triethylenetetramine; X = F⁻, Cl⁻, Br⁻) has been studied in n-alcohol and in formamide at different temperatures, by electrical conductivity measurements. From the CMC values as a function of temperature, various thermodynamic properties have been evaluated: standard Gibbs energy changes (Δ_mic G ⁰), standard enthalpy changes (Δ_mic H ⁰) and standard entropy changes (Δ_mic S ⁰) for micellization. Critical micelle concentrations have also been measured as a function of the percentage composition of alcohol added. The solvent composition dependences of these thermodynamic parameters were determined. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol’s chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols, and the surfactant in the solvent mixture.     

Effect of Alcohols on the CMC and Thermodynamic Functions of Anionic Surfactants in DMF/Long‐Chain Alcohol Using Microcalorimetric Method

The critical micelle concentration (CMC) of two kinds of anionic surfactant (including sodium laurate (SLA) and sodium dodecyl sulfate (SDS)) in mixed alcohol and N, N‐dimethyl formamide solvent (DMF) were investigated through measuring power‐time curves by titration microcalorimetry. From data of the lowest point and the area of the power‐time curves, their CMC and ΔH _m ⁰ can be obtained. According to standard thermodynamic equations, ΔG _m ⁰ and ΔS _m ⁰ also can be calculated. For different surfactant, the influences of the carbon number and the concentration of alcohol on the CMC and standard thermodynamic functions are different in DMF polar medium. These thermodynamic functions for micelle formation can be further interpreted.     

Thermochemistry of the ternary solid complex Gd(C5H8NS2)3(C12H8N2)

The novel ternary solid complex Gd(C₅H₈NS₂)₃(C₁₂H₈N₂) has been obtained from the reaction of hydrous gadolinium chloride, ammonium pyrrolidinedithiocarbamate (APDC), and 1,10-phenanthroline (o-phen · H₂O) in absolute ethanol. The complex was described by an elemental analysis, TG-DTG, and an IR spectrum. The enthalpy change of the complex formation reaction from a solution of the reagents, Δ_r H _m ^ϑ (sol), and the molar heat capacity of the complex, c _m , were determined as being − 15.174 ± 0.053 kJ/mol and 72.377 ± 0.636 J/(mol K) at 298.15 K by using an RD496-III heat conduction microcalorimeter. The enthalpy change of a complex formation from the reaction of the reagents in a solid phase, Δ_r H _m ^ϑ (s), was calculated as being 52.703 ± 0.304 kJ/mol on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of the formation reaction of the complex was investigated by the reaction in solution. Fundamental parameters, the activation enthalpy (ΔH _≠ ^ϑ ), the activation entropy (ΔS _≠ ^ϑ ), the activation free energy (ΔG _≠ ^ϑ ), the apparent reaction rate constant (k), the apparent activation energy (E), the preexponential constant (A), and the reaction order (n), were obtained by the combination of the thermochemical data of the reaction and kinetic equations, with the data of thermokinetic experiments. The constant-volume combustion energy of the complex, Δ_c U, was determined as being −17588.79 ± 8.62 kJ/mol by an RBC-II type rotatingbomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_c H _m ^ϑ , and standard enthalpy of formation, Δ_f H _m ^ϑ , were calculated to be −17604.28 ± 8.62 and −282.43 ± 9.58 kJ/mol, respectively. The text was submitted by the authors in English.     

Studies on the Reaction Kinetics and Mechanism of Iron(II) Reduction of the <Emphasis Type="Italic">cis</Emphasis>-Halogeno(cetylamine)bis(ethylenediamine)cobalt(III) Complex Ion in Aqueous Perchlorate Medium

The electron-transfer kinetics of the ionic surfactant complex cis-chloro/bromo(cetylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous perchlorate medium at μ=1.0 mol⋅dm⁻³ ionic strength have been studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The effects of [H⁺], ionic strength and [Fe²⁺] on the rate were determined. The reaction was found to be second order and showed to be independence of the acid concentration in the range [H⁺]=0.05–0.25 mol⋅dm⁻³. The second order rate constant increased with surfactant–cobalt(III) concentration and the occurrence of aggregation of the complex itself altered the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobal (III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant–metal complexes were obtained in aqueous solution from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependence of the critical micelle concentration (CMC) and the thermodynamics of micellization (ΔG _m^o,ΔH _m^o and ΔS _m^o).     

Studies on Hydrophobic Effect and Micelle Formation of Some Surfactant-Cr(III)-Cetylamine Complexes in Non-aqueous Solvents

Surface active micelle formable surfactant-Cr(III) complexes of the type cis-α-[Cr(trien)(C₁₆H₃₃NH₂)X]²⁺ (where trien = triethylenetetramine; X = F⁻, Cl⁻, Br⁻) have been studied in n-alcohol and in formamide at different temperatures by conductance measurements. Standard Gibbs energy changes (ΔG ^o _mic), enthalpies (ΔH ^o _mic) and entropies (ΔS ^o _mic) of micelle formation have been determined by studying the variation of the Critical Micelle Concentration (CMC) with temperature. Critical micelle concentrations have also been measured as a function of percentage concentration of alcohol added. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols and the surfactant in the solvent mixture.     

Interaction Between Levamisole Hydrochloride and Bovine Serum Albumin and the Influence of Alcohol: Spectra

The interaction between levamisole hydrochloride (LH) and bovine serum albumin, BSA, has been studied by a spectral method under physiological conditions. For 1:n complexes, the relationship between fluorescence quenching intensity and concentration of the quenchers can be deduced on the basis of the modified Stern–Volmer equation. The binding constants and corresponding thermodynamic parameters ΔH _m, ΔG _m and ΔS _m at different temperatures were calculated. The experimental results demonstrated that the combination reaction of LH and BSA was a static quenching process because a 1:1 complex was formed, and the main dominant binding forces were hydrogen bonding and van der Waals forces. Meanwhile, the polarity of the tyrosine residue (Tyr) or tryptophan residue (Trp) micro-region was not obviously affected by the interaction. Furthermore, the binding constant increase when alcohol was added.     

Conductometric studies of hexadecyltrimethylammonium bromide in aqueous solutions of ethanol and ethylene glycol

The effect of cosolvent on micellization of hexadecyltrimethyl ammonium bromide (CTAB) in aqueous solutions was studied. The conductivity of a mixture (cosolvent + water) as function of CTAB concentration was measured at different temperatures. Ethylene glycol and ethanol were used as a cosolvent. The conductivity data were used to determine the critical micelle concentration (CMC) and the effective degree of counterion dissociation of micelle in the temperature range 303.2 to 313.2 K. In all the cases studied, a linear relationship between log([CMC]_mix/mol dm⁻³) and the mass fraction of cosolvent in solvent mixture has been observed. The free energy (ΔG _mic ⁰ ), enthalpy (ΔH _mic ⁰ ), and entropy (ΔS _mic ⁰ ) of micellization were determined using the temperature dependence of CMC. The dependence of these thermodynamic parameters on solvent composition was determined. The standard free energy of micellization was found to be negative in all cases and becomes less negative as the cosolvent content increases. The enthalpy and entropy of micellization are independent of temperature in pure water, while ΔH _mic ⁰ and ΔS _mic ⁰ decrease dramatically with temperature in mixed cosolvents. Furthermore, the entropic contribution is larger than the enthalpic one in pure water, while in the mixed solvents, the enthalpic contribution predominates. The text was submitted by the authors in English.     

Microcalorimetric Studies on the CMC and Thermodynamic Functions of a Nonionic Surfactant (Tween80) in DMF/Long-Chain Alcohol Systems from <Emphasis Type="Italic">T</Emphasis>=298.15 to <Emphasis Type="Italic">T</Emphasis>=313.15 K

The power-time curves of the micelle formation process were determined for the nonionic surfactant Tween80/nonaqueous solvent (DMF)/long-chain alcohol (n-heptanol, n-octanol, n-nonanol, and n-decanol) systems by titration microcalorimetry at temperatures of (298.15, 303.15, 308.15, and 313.15) K. From the power-time curves, the CMC and DH_m^\uptheta\Delta H_{\mathrm{m}}^{\uptheta} values were obtained. The corresponding values of DG_m^\uptheta\Delta G_{\mathrm{m}}^{\uptheta} and DS_m^\uptheta\Delta S_{\mathrm{m}}^{\uptheta} were also calculated. The relationships of the CMC with the carbon number of the alcohol, the concentration of alcohol, and the temperature, along with the thermodynamic functions, are discussed.     

Micellization of Metallosurfactant N-Dodecyl/Hexadecyl/Octadecyl Salicylaldimine Cobalt(III) Complexes in Nonaqueous Media

Abstract The critical micelle concentrations (CMC) of three metallosurfactant Schiff base cobalt(III) complexes of the type [Co(trien)(C₁₉H₃₀NO)]Cl₂,[Co(trien) (C₂₃H₃₈NO)]Cl₂ and [Co(trien)(C₂₅H₄₂NO)]Cl₂, where trien = triethylenetetramine, have been studied in n-alcohol and in formamide at different temperatures by the electrical conductivity method. CMCs have also been measured as a function of percentage concentration of alcohol in the mixed solvents with formamide. Specific conductivity data (at 303–323 K) served for the evaluation of the temperature-dependent CMC and thermodynamic parameters such as the standard Gibbs energy changes (DG^°_mic)\Delta G^{\circ}_{\mathrm{mic}}), enthalpy changes (DH^°_mic)\Delta H^{\circ}_{\mathrm{mic}}), and entropy changes (DS^°_mic)\Delta S^{\circ}_{\mathrm{mic}}) of micelle formation. It is suggested that addition of an alcohol leads to increased penetration of formamide into the micellar interface, the extent depending on the alcohol’s chain length. The results have been discussed in terms of the solvophobic interaction, dielectric constant of the medium, the chain length of the alcohol, and the surfactant in the solvent mixture.     

Metallosurfactants of Chromium(III) Coordination Complexes. Synthesis, Characterization and Determination of CMC Values

A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)₂(A)X]²⁺ and cis-α-[Cr(trien)(A)X]²⁺ (A = Dodecyl or Cetylamine; X = F⁻, Cl⁻, Br⁻) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ G_m⁰, Δ H_m⁰ and Δ S_m⁰).     

A temperature study on critical micellization concentration (CMC), solubility, and degree of counterion binding of α-sulfonatomyristic acid methyl ester in water by electroconductivity measurements

 For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around 0 °C. The changes in the Gibbs energy, ΔG ⁰ _m, enthalpy, ΔH ⁰ _m, and entropy, ΔS ⁰ _m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation. Received: 28 August 1996 Accepted: 5 November 1996     

Study on Inclusion Complex Formation of <Emphasis Type="Italic">m</Emphasis>-Aminobenzoic Acid with Native and Substituted <Emphasis Type="Italic">β</Emphasis>-Cyclodextrins

The complex formation of native and substituted β-cyclodextrins with m-aminobenzoic acid in water was characterized by calorimetry, ¹H NMR and UV spectroscopic studies. These studies showed that β-, hydroxypropyl-β- and methyl-β-cyclodextrins form 1:1 inclusion complexes with m-aminobenzoic acid. The thermodynamic properties of complex formation (K,Δ_c G ^o,Δ_c H ^o,Δ_c S ^o) were calculated. It was found that the processes of complexation are mainly favorable entropically. Introduction of hydroxypropyl- and methyl-substituents into the β-CD molecule results in negligible enhancement of stability of the complexes formed. The structure of these substituents has no influence on the stability constant values. The insertion of the carboxylic group of m-aminobenzoic acid into the cyclodextrin cavity was confirmed by ¹H NMR data.     

A model developed for acid dissolution thermodynamics of a Turkish bentonite

A model was proposed to calculate some thermodynamic parameters for the acid dissolution process of a bentonite containing a calcium-rich smectite as clay mineral along with quartz, opal and feldspar as impurities. The bentonite sample was treated with H₂SO₄ by applying dry method in the temperature range 50–150°C for 24 h. The acid content in the dry bentonite-sulphuric acid mixture was 45 mass%. The total content (x) of Al₂O₃, Fe₂O₃ and MgO remained in the undissolved sample after treatment was taken as an equilibrium parameter. An apparent equilibrium constant, K _a, was calculated for each temperature by assuming K _a=(x _m−x)/x where x _m is the total oxide content of the natural bentonite. Also, an apparent change in Gibbs free energy, ΔG _a^o, was calculated for each temperature by using the K _a value. The graphs of lnK _a vs. 1/T and ΔG _a^o vs. T were drawn and then the real change in both the enthalpy, ΔH ^o and the entropy, ΔS ^o, values were calculated from the slopes of the straight lines, respectively. Inversely, real ΔG ^o and K values were calculated from the real ΔH ^o and ΔS ^o values through ΔG ^o = −RT ln K = ΔH ^o − TΔS ^o equation. The best ΔH ^o and ΔS ^o fittings to this relation were found to be 65687 J mol⁻¹ and 164 J mol⁻¹K⁻¹, respectively.     

An Inclusion Compound of the Anticonvulsant Sodium Valproate into α-Cyclodextrin: Physico-Chemical Characterization

A non-hygroscopic pharmaceutical composition was obtained following a host-guest strategy that used the anticonvulsant drug sodium valproate (VA) and α-cyclodextrin. The pharmaceutical composition was fully characterized by thermal analyses (TG/DTG, DSC), X-ray powder diffraction and by ¹H, ¹³C, hydrogen relaxation times (T₁) and 2D-ROESY NMR techniques. Isothermal titration calorimetry (ITC) was used to determine the VA:α-CD 1:1 stoichiometry as well as to calculate the equilibrium constant (K) and thermodynamic energies of interaction (ΔG^o, ΔH^o and TΔS^o).     

Thermodynamic characteristics of hydrated acrylamide and polyacrylamide complexes of cobalt nitrate at <Emphasis Type="Italic">T</Emphasis> → 0 to 380 K

The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic calorimetry. This evidence makes it possible to calculate thermodynamic functions C _p ^ℴ(T), H ^ℴ(T) − H ^ℴ(0), S ^ℴ(T), G ^ℴ(T) − H ^ℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcH ^ℴ; and the thermodynamic parameters of formation, Δ _f H ^ℴ, Δ _f S ^ℴ, and Δ _f G ^ℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy Δ_pol H ^ℴ, entropy Δ_pol S ^ℴ, and Gibbs function Δ_pol G ^ℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K.     

Conductivity Studies of <Emphasis Type="Italic">n</Emphasis>-Tetrabutylammonium Tetraphenylborate in 3-Pentanone in the Temperature Range from 283.15 to 329.15 K

The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu₄BPh₄) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λ_o) and the association equilibrium constants (K _A) have been derived. The limiting ion conductivities (λ_±^o) have been evaluated according to the method of Krumgalz. The λ₊ ^o values have been compared with λ₊ ^o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G _A ^o), enthalpy (Δ H _A ^o) and entropy (Δ S _A ^o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH ^∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions.     

Solid-Solute Phase Equilibria in Aqueous Solutions XIV [1]. Thermodynamic Analysisof the Solubility of Hellyerite in Water

 The solubility of hellyerite, NiCO₃ · 6H₂O, in water was studied at different temperatures. From the experimental data obtained, a preliminary set of the thermodynamic quantities Δ_f G ^⊖, Δ_f H ^⊖, and S ^⊖ for hellyerite was derived using the ChemSage optimizer routine.