Aqueous Bromide Solutions Research Articles

Apparent and partial molar volumes of long-chain alkyldimethylbenzylammonium chlorides and bromides in aqueous solutions at T=15 °C and T=25 °C

Density measurements of dodecyl- (C 12DBACl), tetradecyl- (C 14DBACl), hexadecyldimethylbenzylammonium chloride (C 16DBACl) and of decyl- (C 10DBABr) and dodecyldimethylbenzylammonium bromide (C 12DBABr) in aqueous solutions at T=15 °C and T=25 °C have been carried out. From these results, apparent and partial molar volumes were calculated. Positive deviations from the Debye–Hückel limiting law provide evidence for limited association at concentrations below the critical micelle concentration. The change of the apparent molar volume upon micellization was calculated. The relevant parameters have been presented in function of the alkyl chain length. Apparent molar volumes of the present compounds in the micellar phase, V φ m, and the change upon micellization, Δ V φ m, have been discussed in terms of temperature and type of counterion.

Effect of Amides on the Micellar Behavior of a Cationic Surfactant Tetradecyltrimethylammonium Bromide in Aqueous Solution

Effect of Amides on the Micellar Behavior of a Cationic Surfactant Tetradecyltrimethylammonium Bromide in Aqueous Solution

Influence of the addition of alcohol on the reaction methyl-4-nitrobenzenesulfonate + Br − in tetradecyltrimethylammonium bromide aqueous micellar solutions

The reaction methyl-4-nitrobenzenesulfonate + Br − was studied in tetradecyltrimethylammonium bromide (TTAB) aqueous micellar solutions in the absence and in the presence of various amounts of n-hexanol, n-pentanol, and n-butanol. Kinetic micellar effects provoked by the addition of the linear alcohols can be rationalized by using simple pseudophase kinetic models. The equilibrium binding constants of the methyl-4-nitrobenzenesulfonate molecules to the cationic micelles decreases when [alcohol] increases. The ( k 2 m / V m ) values found are practically the same for the different TTAB–alcohol micellar solutions studied, independent of the nature and concentration of the alcohol present in the reaction medium. This has been explained by considering the balance of two factors operating on reactivity in opposite ways: (1) an increase in the volume of the micellar interfacial region upon increasing alcohol concentration, and (2) a decrease in the polarity of the interfacial region as the amount of alcohol present in the micellar solutions increases.

Photodegradative Surfactants: Photolysis of p‐Dodecylbenzyltrimethylammonium Bromide in Aqueous Solution.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Ionic strength effects on hexadecane contact angles on a gold-coated glass surface in ionic surfactant solutions

Abstract As aqueous surfactant cleaning becomes increasingly prevalent in industry, an understanding behind surfactant cleaning behavior is needed to improve the systems. Improvements in these aqueous surfactant solution systems can reduce the impact of the industrial cleaning systems on the environment and improve their efficiency. Studying various parameters of the cleaning systems can provide useful insight into surfactant behavior. The contact angle of the soil to the solid surface is strongly related to cleaning system performance and is a relatively simple parameter to measure. For this study, a simplified cleaning system was studied to investigate the effects of modifications to the surfactant system. The contact angle of hexadecane on a gold-coated glass surface in aqueous surfactant solutions of sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) were determined up to and above the critical micelle concentrations. The effects of modifying the ionic strength of the aqueous surfactant solution by the addition of sodium chloride (NaCl) have been studied. Similar trends in contact angle behavior of the oil droplet to the gold-coated surface were found for both the anionic (SDS) and cationic (CTAB) surfactant systems. The addition of NaCl to the aqueous surfactant systems resulted in a significant increase in the contact angles over the surfactants concentration ranges. The increasing trend in the contact angles was observed for NaCl concentrations ranging from 0.05 to 0.5 mM, while little effect was noted for the higher NaCl concentrations. The observed effect is consistent with literature on electrostatic-charge-induced changes in surfactant adsorption at the solid surface.

Kinetics of 2-Naphthyl Acetate Hydrolysis Catalyzed by α-Chymotrypsin in Aqueous Solutions of Dodecyltrimethylammonium Bromide

The rate of hydrolysis of 2-naphthyl acetate catalyzed by α-chymotrypsin has been measured in aqueous solutions of dodecyltrimethylammonium bromide at concentrations below and above the critical micelle concentration, as well as in the absence of surfactant. Under all the conditions employed, the reaction takes place following a Michaelis−Menten mechanism. The presence of the surfactant, at concentrations above its critical micellar concentration, increases the value of the Michaelis constant, Km, without significant changes in the catalytic rate constant, kcat. The increase in Km is larger than that expected from the incorporation of the substrate to the micellar pseudophase, indicating that the interaction between the enzyme and micellelike aggregates alters the formation of the enzyme−substrate complexes. This can be related to a partial unfolding of the enzyme, as is suggested by changes in its intrinsic fluorescence.

Mixed micelles of cationic–nonionic surfactants: NMR self-diffusion studies of Triton X-100 and cetyltrimethylammonium bromide in aqueous solution

The Fourier transform pulsed-field-gradient NMR technique has been used to measure the self-diffusion coefficients of the two surfactants cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in their mixed aqueous solutions with various molar ratios of CTAB to TX-100. Through simulating these experimental values of the self-diffusion coefficients by the two-state exchange model, some important dynamical micellization parameters, such as the critical micellar concentration of each soltute, the critical mixed micellar concentration and the self-diffusion coefficient of the mixed micelles at various molar ratios have been obtained. The composition of the mixed micelles and the interaction parameters between the two surfactants have also been evaluated. The mixed-micellization processes were discussed on the basis of these parameters. The results demonstrate the advantages of using NMR self-diffusion measurements to study binary cationic–nonionic mixed systems.

Solubilization of a water-insoluble dye in aqueous NaBr solutions of alkylpyridinium bromides and its relation to micellar size and shape

In order to investigate the effect of added salt on micelle size, shape, and structure the solubilization of Orange OT in aqueous NaBr solutions of decylpyridinium bromide (DePB), dodecylpyridinium bromide (DPB), tetradecylpyridinium bromide (TPB), and hexadecylpyridinium bromide (CPB) has been examined. The solubilization powers of DePB and DPB micelles increase with increasing NaBr concentration up to 2.86 and 3.07 mol dm–3, respectively, but above these concentrations remain unaltered. This suggests that spherical micelles of DePB and DPB can have a maximum and constant size at NaBr concentrations higher than these threshold concentrations. On the other hand, the solubilization powers of TPB and CPB micelles increase in the whole range of NaBr concentration studied. The dependencies of the solubilization powers of their micelles on the counterion concentration change at 0.10 and 0.03 mol dm–3 NaBr, respectively, as suggests that TPB and CPB micelles undergo the sphere–rod transition at those concentrations. Orange OT is a more suitable probe for detecting the presence of the maximum- and constant-size spherical micelle than Sudan Red B.

Formation of PbBr-Based Layered Perovskite Structure Having Poly(thiophene) as an Organic Layer by Soaking Thin Film of Hydrogen Bromide Salt of Poly(3-aminododecylthiophene) in Aqueous Lead Bromide Solution

Abstract When a spin-coated film of hydrogen bromide salt of poly(3-aminododecylthiophene), PC12T·HBr, was soaked in an aqueous solution of PbBr2, PbBr-based layered perovskite structure combined with a semiconductor layer of two-dimensional sheets of PbBr6 octahedra and an organic semiconductor layer of poly(thiophene) was formed.

Interfacial Films and Wetting Behavior of Hexadecane on Aqueous Solutions of Dodecyltrimethylammonium Bromide

The interfacial tensions and dihedral angles of hexadecane lenses on aqueous solutions of dodecyltrimethylammonium bromide (DTAB) were measured in air as a function of the molality of DTAB at 298.15 K and atmospheric pressure. The air/water interfacial tension of DTAB solution shows a break point that shifts to a lower concentration in the presence of a hexadecane lens. Ellipsometric measurements showed a continuous variation in ellipticity with concentration for pure DTAB solutions, but a discontinuous change in the ellipticity of the air/water interface in the presence of a hexadecane lens. This behavior can be viewed either as a first-order wetting transition driven by the adsorbed surfactant, or as a gaseous-expanded phase transition in the surfactant adsorbed film induced by the hexadecane. The formation of a microscopic oil film in equilibrium with a lens is rationalized by an attractive long-range potential across the thin film. From the measurement of dihedral angles, it was found that there was a concentration region where a lens exists stably even when complete wetting was expected from measured values of interfacial tensions.

Micellization of dodecyldimethylethyl- ammonium bromide in aqueous solution

Specific conductivity of aqueous solutions of dodecyldimethylethylammonium bromide has been determined in the temperature range of 15–40°C. The critical micelle concentration (cmc) and ionization degree of the micelles, β, were determined from the data. Thermodynamic functions, such as standard Gibbs free energy, ΔGm ∘ , enthalpy, ΔH m ∘ , and entropy, ΔS m ∘ , of micellization, were estimated by assuming that the system conforms to the mass action model. The change in heat capacity upon micellization, ΔC p,m ∘ , was estimated from the temperature dependence of ΔH m ∘ . An enthalpy-entropy compensation phenomenom for the studied system has been found.

Quaternary mutual diffusion coefficients for aqueous solutions of a cationic–anionic mixed surfactant from moments analysis of Taylor dispersion profiles

Taylor dispersion is used to measure mutual diffusion in aqueous solutions of dodecyltrimethylammonium bromide (DTAB) + sodium octanoate (NaOct), a cationic–anionic mixed surfactant. Diffusion of the four different constituent ions (DTA+, Br−, Na+, Oct−) constrained only by electroneutrality produces three independent solute fluxes. Mutual diffusion in these solutions is therefore a quaternary process described by nine Dik coefficients. Injecting excess DTAB or NaOct into DTAB + NaOct carrier solutions produces remarkable refractive-index profiles with three maxima and two minima. Least-squares analysis of these profiles failed to converge, prompting the development of a procedure for the evaluation of quaternary Dik coefficients from the heights, areas, first moments, and second moments of dispersion profiles. The reported Dik coefficients describe the coupled diffusion of DTAB(1) + NaOct(2) + NaBr(3) components in solutions containing 40 mmol dm−3 total surfactant at 25 °C and four different DTAB:NaOct ratios. The results show that the unusual profile shapes are caused by strongly coupled diffusion, as indicated by large negative D12, D21 values and large positive D32, D31 values which exceed the magnitude of main-coefficients D11 and D22. Binary mutual diffusion coefficients for aqueous DTAB solutions and critical micelle concentration for DTAB + NaOct solutions are also reported.

Kinetics and Mechanism of the Reaction of Ninhydrin with Chromium(III)-tryptophan Complex in Absence and Presence of Surfactants

The kinetics of the title reaction have been investigated in both aqueous and micellar cetyltrimethylammonium bromide(CTAB) solutions. Rate data indicate that the reaction follows the template mechanism in both the media. The observed rate constant is affected by [CTAB] changes and the maximum rate enhancement is ca. 4 -fold. The following parameters have been calculated at pH 5.0: for aqueous, kobs = 5.6 χ 10-5 s-1, ΔH* = 61 k J mol-1, ΔS* = -122 J K-1mol-1 ; for CTAB , kΨ = 24.7 χ 10-5 s-1 , ΔH* = 35 k J mol-1, ΔS* = -200 J K-1 mol-1, which reveal CTAB behaving as a catalyst. To explain the dependence of the reaction rate on [CTAB], pseudo-phase model proposed by Menger and Portnoy and modified by Bunton and Rodenas was used. The catalytic role of CTAB can be related to the extent of incorporation or association of the chromium(III)-tryptophan and ninhydrin into the micelles. Various factors which affect km, Ks KN and are discussed taking into account the micellar surface solvent properties.

Study of the 1-chloro-2,4-dinitrobenzene + oh- reaction in tetradecyltrimethylammonium bromide aqueous micellar solutions

The 1-chloro-2,4-dinitrobenzene + OH- reaction was studied in tetradecyltrimethylammonium bromide aqueous micellar solutions. Influence of changes in [surfactant] as well as in [NaOH] on the observed rate constant were rationalized by using pseudophase kinetic models. At high hydroxide ions concentration an additional pathway across the micellar boundary had to be considered.

Mathematical Modeling and Simulation for Marangoni Convection by Surfactants in Liquid Falling Film.

In an absorption refrigeration system, it is well known that water vapor absorption into lithium bromide (LiBr) aqueous solution is enhanced by the addition of surfactants. Marangoni convection plays a role but its mechanism has not clearly been understood yet. In the present study, a relation between heat and mass transfer and Marangoni convection was investigated using mathematical modeling and numerical simulation in a falling film type absorber. We used an advanced Marangoni convection model that is able to predict velocity, temperature and mass fraction distribution in a falling film type absorber. Firstly, the effect of Marangoni convection on heat and mass transfer in an absorber was examined. As a result, efficiency of heat and mass transfer was increased due to Marangoni convection. Secondly, analysis for the effects of different operating conditions on an onset of Marangoni convection was carried out. The Marangoni number for the onset of convection decreased as the initial temperature and initial water mass fraction of solution decreased.

Effects of Ultrasonic Vibration on Heat Transfer Characteristics of Lithium Bromide Aqueous Solution under the Reduced Pressure

Effects of Ultrasonic Vibration on Heat Transfer Characteristics of Lithium Bromide Aqueous Solution under the Reduced Pressure

B213 吸収冷凍機における高効率吸収器の開発

Pre-cooling venturi type absorber for absorption heat pump was experimentally investigated to increase vapor absorption rates. In this research, the absorbent is pre-cooled at 35-45℃ before the nozzle, and we examine how much the lithium bromide aqueous solution can absorb the vapor by the proposed venturi type absorption rate of the solution increases as the inlet pressure increases. The ratio of the absorption rate to the flow rate of the absorbent is about 3-5%.

Development of first-principles interaction model potentials. An application to the study of the bromide hydration

This work presents the development of first-principles bromide ion–water interaction potentials using the mobile charge density in harmonic oscillators-type model. This model allows for a flexible and polarizable character of the interacting molecules and has already been parametrized for water–water interactions. The prospected potential energy surfaces of the bromide ion-water system were computed quantum-mechanically at Hartree–Fock and Møller–Plesset second-order perturbation levels. In addition to the ion–solvent molecule pair, structures formed by the anion and two or three water molecules were considered in order to include many body effects. Minimizations of hydrated bromide clusters in gas phase [Br(H2O)n]− (n=1–6,10,15,20) and Monte Carlo computations of bromide aqueous solutions were performed to test the new potentials. Both structural and thermodynamic properties have been studied in detail and compared to the available experimental and theoretical values. From these comparisons, it was concluded the importance of including basis set superposition error corrections for the two-body interactions, and the small role of both electron correlation on the three-body terms and the four-body terms. Monte Carlo simulation results have also been used to investigate if the presence of the anion significantly affects the intramolecular geometry of the water molecules and the degree of disruption of the water solvent structure in its vicinity.

Mixed Micellization of Dodecylethyldimethylammonium Bromide and Dodecyltrimethylammonium Bromide in Aqueous Solution

Conductivity and steady-state fluorescence measurements have been carried out at 25 °C to study the monomeric and micellar phases of the aqueous solutions of the mixed system constituted by two cationic surfactants, dodecylethyldimethylammonium bromide and dodecyltrimethylammonium bromide. From conductivity data, the total critical mixed micellar concentration, cmc*, and the dissociation degree of the mixed micelle, β, have been obtained, while fluorescence experiments allow for the determination of the total aggregation number, N*, and the micropolarity of the micellar inside. A new experimental method has been designed to determine the partial contribution of each surfactant to the mixed micellization process, through their critical micellar concentrations, cmc1* and cmc2*, and their aggregation numbers, N1* and N2*. A phenomenological limit mixed micellization line is proposed to define the limit conditions to form mixed micelles. The mixing of two cationic surfactants of identical tail but polar heads...

Sonochemical behavior of aqueous solutions of iodide, bromide and azide

The sonolysis of azide solutions was investigated. The main product is nitrogen, which is formed in the reaction of N3− with OH radicals in the millimolar concentration range. At higher azide concentration, additional nitrogen is formed as hydrogen atoms are scavenged. Ammonia and hydrazine are minor products of the N3− sonolysis. Solutions of iodide and bromide are also irradiated under pH conditions where reactions of the products, i.e., hydrogen per oxide and iodide (or bromide) do not occur. The total yield of the products as well as the hydrogen yield is independent of the solute concentration. The results are understood in terms of the competition of the OH+OH and the OH+solute reactions. A local concentration of 4 × 10−3 mol/L of the OH radicals in an interfacial region between the cavitation bubbles and the liquid is derived from the data obtained.