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1.
The enthalpies of mixing of some n-nitriles (from acetonitrile to valeronitrile) aqueous solutions with dodecyltzimethylammonium bromide, sodium dodecylsulfate and dodecyltzimethylammonium oxide micellar solutions were determined. The measurements were performed by systematically changing the surfactant concentration at a given solute concentration. The experimental enthalpies were rationalized in terms of the standard enthalpy of transfer of solute from the aqueous to the micellar phase and of the distribution constant between the two phase. Information on the effect of the nature of the surfactant on the standard thermodynamic quantities of transfer(G
t
o
, H
t
o
, TS
t
o
) is reported. The present data are compared to those previously reported for primary alcohols and the solubilizing properties shown by the different types of micelles are discussed. 相似文献
2.
Diffusion coefficients of tetradecyltrimethylammonium bromide in aqueous solutions have been determined at 25, 95 and 135 °C using the Taylor dispersion technique. The diffusion coefficient exhibits a minimum at a surfactant concentration above the critical micelle concentration (CMC). The results are interpreted in terms of electrostatic coupling and rapid exchange between micelle, surfactant monomer and counterions. 相似文献
3.
C. Aucouturier G. Roux-Desgranges A. H. Roux 《Journal of Thermal Analysis and Calorimetry》1994,41(6):1295-1303
Interactions of a series of polyethyleneglycols (PEG) in aqueous micellar solutions of sodium dodecylsulfate (SDS) were investigated through thermodynamic properties. Volumes, heat capacities and enthalpies of dilution were measured at 25°C. The resulting transfer properties of PEG are reflecting hydrophobic interactions which increase with the polymer length and the hydrophilic interactions occurring in the aqueous polar layer of the micelles. Typically heat capacities clearly evidence various structural changes taking place in the micellar solutions. 相似文献
4.
在高压釜式反应器中考察了添加过氧化特二丁基(DTBP)、偶氮二异丁腈(AIBN)和单质碘(I2)三种自由基引发剂对克拉玛依蜡油、孤岛减压渣油加氢裂化反应的影响。在氢气初始压力7.0 MPa,反应1 h的条件下,对引发剂用量、催化剂用量、反应温度等影响因素进行了考察。结果表明,添加自由基引发剂后,重油的加氢裂化转化率,轻质油收率以及HDS、HDN都明显增加。添加质量分数5 000×10-6或10 000×10-6引发剂后,蜡油和减压渣油加氢裂化的轻质油收率最大可增加10%、13%,HDS和HDN最大可增加11%和7%左右。采用较少的催化剂用量或较低的反应温度即可以实现较高的重油转化率和轻质油收率。相对而言,DTBP和I2的促进作用优于AIBN。添加引发剂前后的加氢裂化的产物分布对比说明,引发剂的加入有利于蜡油或渣油原料一次裂化产物的生成。 相似文献
5.
基于热裂化按照自由基反应机理进行的特点,在高压釜式反应器中分别添加四种自由基引发剂偶氮二异丁腈(AIBN)、过氧化特二丁基(DTBP)、单质硫(S)和单质碘(I2),考察引发剂在390℃~410℃,引发剂添加量0~3000×10-6条件下对三种减压渣油减黏裂化的影响。通过测定减黏前后渣油的运动黏度和四组分的变化,对引发剂的作用机理进行了初步研究。结果表明,自由基引发剂对不同基属的减压渣油减黏裂化反应均有明显的促进作用,大小依次为:LHVR≥GDVRDQVR,并且这种促进作用在较低的反应温度下更加明显,促进效果由渣油本身的物理化学性质所决定。在同等条件下,I2和S促进渣油减黏的效果是AIBN和DTBP降黏率的两倍,这与S和I2形成氢化物的"活性原子"可以多次循环发生作用有关。与S相比,单质I2减黏促进作用更为明显。 相似文献
6.
Shagidullina R. A. Zakharova L. Ya. Valeeva F. G. Kudryavtseva L. A. 《Russian Chemical Bulletin》2001,50(7):1181-1185
The micellar effect of cationic surfactants in alkaline hydrolysis of O-alkyl-O-aryl-chloromethyl phosphonates involves a positive contribution of concentrating the reagents and a negative effect of the micellar environment due to a loss in the activation entropy. The reactivity of substrates in micelles depends on both electronic and hydrophobic characteristics of substituents in the aryl group. 相似文献
7.
J. J. Galán A. González-Pérez J. A. Seijas E. Uriarte J. R. Rodríguez 《Colloid and polymer science》2005,283(4):456-460
Electrical conductivity of aqueous solutions of tetradecylpyridinium bromide and chloride has been measured as a function of surfactant molal concentration and temperature. From the molal dependence of conductivity, the critical micelle concentration and the micellar ionization degree were estimated. The temperature dependence of these parameters has been used for calculating the thermodynamic parameters related with the micellization process by using the classical charged pseudophase separation model. The effect of the counterion on the conventional thermodynamic potentials of micellization such as standard Gibbs free energy, enthalpy and entropy has also been a matter of study. Finally, the occurrence of the enthalpy–entropy compensation phenomenon was verified and the relevant parameters discussed. 相似文献
8.
The combination of the water-soluble radical initiator, 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (VA-061), water-soluble chain carrier, 1-ethylpiperidine hypophosphite (EPHP) and surfactant, cetyltrimethylammonium bromide (CTAB), was found to be the most suitable condition for effective radical cyclization in water for a variety of hydrophobic substrates. The effect of additives and surfactant in the radical cyclization reaction in water was also investigated. 相似文献
9.
Living radical polymerizations of acrylate are known to be difficult to achieve using TEMPO as a mediator. The stable free radical polymerization (SFRP) of acrylate tends to stop at low monomer conversion due to the accumulation of TEMPO in the medium as a result of unavoidable bimolecular termination. Rather than solving this problem by destroying the excess nitroxide using ascorbic acid or glyceraldehyde associated with pyridine as reported recently, high temperature initiators were used to slowly and continuously generate new radicals throughout the polymerization to consume the excess TEMPO molecules. Polymerizations of n-butyl acrylate initiated by the alkoxyamine unimer (1-benzoyloxy)-2-phenyl-2-(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)ethane (BST) were performed between 130 °C and 134 °C in the presence of a series of high temperature peroxide and azo initiators. The best results in this study were obtained by the continuous addition of small amounts of di-tert-amyl peroxide throughout the polymerization. Under these conditions, the acrylate polymerizations fulfilled the criteria of a controlled polymerization process although the molecular weight distributions were slightly broad (Mw/Mn ∼ 1.5). 相似文献
10.
The exces enthalpies of solution of some primary and secondary alcohols in aqueous sodium dodecylsulfate micellar solutions were measured and the results were explained by considering the distribution of alcohols between aqueous and micellar phases. The distribution constant and the enthalpy of transfer (and the standard free energy and entropy of transfer) were obtained. The thermodynamic parameters for the transfer of secondary alcohols from the aqueous to the sodium dodecylsulfate (NaDS) micellar phase differ slightly from those of the corresponding primary alcohols. For both series of alcohols the additivity rule holds for free energies of transfer whereas enthalpies and entropies display convex curves. The present data are compared to those for the transfer of the same solutes from the aqueous to the dodecyldimethylamine oxide (DDAO) and dodecyltrimethylammonium bromide (DTAB) micellar phases. The role of the hydrophilic interactions between the OH group and the micelles' head groups is formulated. The thermodynamics of the branched methyl group were determined. Furthermore, the thermodynamics of solvation of primary alcohols in water, in NaDS micelles, and in octane have been calculated using reference states based on the assumption that the empty space around alcohols in the initial and final states is the same. It is shown that the solvation of alcohols in NaDS micellar phase is enthalpy driven and that the thermodynamic properties of solvation vs. the length of the alcohol tail is the same for water and NaDS micelles whereas it is different for octane. A possible explanation for this difference is that the alkyl chain of alcohols folds in octane. 相似文献
11.
EMF measurements in water at 25°C have been made using surfactant ion and counterion electrodes on two homologous series of long chain surfactants, the sodium alkylsulfates (R=n-C8H17 to n-C14H29) and the alkyltrimethylammonium bromides (R=C10H21 to C16H33). The data show evidence of association below the critical micelle concentration (CMC) but not of micelle ordering due to coulombic repulsion above this concentration. 相似文献
12.
Rosario De Lisi Calogero Genova Rosaria Testa Vincenzo Turco Liveri 《Journal of solution chemistry》1984,13(2):121-150
Densities of the ternary system water-sodium dodecylsulfate (NaDS)-pentanol and of the binary systems butanol-octane and pentanol-octane were measured at 15, 25, and 35 °C. The apparent molar volume of pentanol in the ternary system was analyzed using a mass-action model for the alcohol distribution in micellar solutions. The partial molar volume of alcohol bound to the micelles and the ratio between the binding constant and the aggregation number of the surfactant are calculated. The partial molar volume binding constant, is discussed in terms of solubilization sites of the alcohol in the micelles whereas the binding constant is compared with that derived from the Nernstian partition constant previously obtained calorimetrically. From the binding constant and Poisson statistics the distribution function of the number of alcohol molecules per micelle, as a function of the concentration of alcohol and of surfactant, are calculated. The derived distribution functions show that a large amount of alcohol can be solubilized in the micelles so that alcoholic mixed micelles can be predicted when the concentration of pentanol is greater than that of NaDS. 相似文献
13.
The decomposition of ammonium nitrite in water creates a supersaturated solution of nitrogen. The same process occurs in water-organic solvent mixtures. Acetone, dioxane, dimethylsulfoxide (DMSO) and dimethylformamide (DMF) are the cosolvents used in this study. The limits of supersaturation of nitrogen (C
SL
/mol L–1) were determined in all of these solvent mixtures by releasing the dissolved gas sonicationally and measuring the volume of released gas. C
SL
was generally increased in the presence of cosolvents. The effectiveness sequence of organic solvents was found to be as DMF
SL
and all of the measured quantities of this study were generally affected by micelle formation. 相似文献
14.
15.
The enthalpies of solution and of dilution of 1-butanol and 1-pentanol were measured in micellar solutions of dodecyltrimethylammonium bromide by systematically changing the concentration of alcohols and surfactant. The enthalpies of solution at infinite dilution of alcohols at each surfactant concentration were evaluated from a linear plot. This quantity increases with surfactant concentration (up to 0.8m) with a curvature which depends on the alcohol alkyl chain length. The difficulties arising for a quantitative treatment of both the enthalpies of dilution and of solution at finite alcohol concentrations are discussed. The dependence on the surfactant concentration of the standard enthalpies of solution and the enthalpies of dilution for m0 are rationalized. From the resulting equations the distribution constant, standard enthalpy of transfer, standard enthalpy of solution, and the alcohol-alcohol interaction parameter in the micellar phase are evaluated. The enthalpies of transfer obtained using this technique agree well with those previously reported from enthalpies of mixing. The distribution constants also agree with those reported in the literature from several approaches: mixing enthalpies, partial molar volumes, and the dependence of the cmc on added alcohol. 相似文献
16.
A. B. Mirgorodskaya L. A. Kudryavtseva L. Ya. Zakharova V. E. Bel'skii 《Russian Chemical Bulletin》1998,47(7):1296-1301
The effects of cetylpyridinium bromide (CPB) on the acid-base equilibria of primary aliphatic amines and on the kinetics of
reactions of the amines withp-nitrophenyl acetate (PNPA) andp-nitrophenyl caprylate (PNPC) were studied by potentiometric titration and UV spectroscopy. The values of apparent pK
a of the amines in the micellar phase, binding constants of their neutral forms, and the surface potentials of micelles were
determined. Cetylpyridinium bromide accelerates the aminolysis of PNPA by factors of 3 to 8 by forming mixed micellar aggregates
with the amines. The shift of pK
a values of the amines in micellar solutions is not the only factor that enhances their reactivity. The substrate specificity
was found: in contrast to the reaction with PNPA, CPB accelerates (by factors of 15 to 65) or retards (by factors of 4 to
6) the aminolysis of PNPA depending on the hydrophobicity of the nucleophilic reagent. The binding constants of substrates,
the rate constants in the micellar phase, and the critical concentrations of micellization were determined from the data obtained.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1333–1338, July, 1998. 相似文献
17.
Tohru Saitoh Nobutoshi Ojima Hitoshi Hoshino Takao Yotsuyanagi 《Mikrochimica acta》1992,106(1-2):91-99
The partition constants (K
d) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10M [(H+, Na+)Cl–] and at 20 °C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the logK
d values of some metal chelates. The plot of theK
d values with the van der Waals volume of the solute molecules obviously shows the leveling-off of theK
d values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems. 相似文献
18.
Valeeva F. G. Zakharov A. V. Voronin M. A. Zakharova L. Ya. Kudryavtseva L. A. Isaikina O. G. Kalinin A. A. Mamedov V. A. 《Russian Chemical Bulletin》2004,53(7):1563-1571
The data are presented on the synthesis of podands with terminal quinoxaline fragments of rings and their influence on both the micellization properties of cetyltrimethylammonium bromide in a water—DMF solution and kinetics of basic hydrolysis of O-p-nitrophenyl O-ethyl chloromethylphosphonate and O-p-nitrophenyl O-hexyl chloromethylphosphonate in the absence and presence of surfactants. The mechanism of the podand effect on the reaction rate depends on the structures of phosphonate and podand. 1,8-Bis(3-ethyl-1,2-dihydro-2-oxoquinoxalin-1-yl)-3,6-dioxaoctane inhibits the basic hydrolysis of the substrates to 3—4 times. In a micellar solution of the surfactant, an approximately 20-fold acceleration of the reaction rate constant is observed. The observed rate constant decreases when podand is added to a micellar solution. The catalytic effect of the polycomponent system is due to concentrating of the reactants. The micellar microenvironment can exert both positive and negative effects on the reactivity of phosphonates. 相似文献
19.
The kinetics of the gamma-radiation-induced free radical chain reaction in solutions of C2Cl3F in cyclohexane (RH) was investigated over a temperature range of 87.5–200°C. The following rate constants and rate constant ratios were determined for the reactions: In competitive experiments in ternary solutions of C2Cl4 and C2Cl3F in cyclohexane the rate constant ratio k2c/k2a was determined By comparing with previous data for the addition of cyclohexyl radicals to other chloroethylenes it is shown that in certain cases the trends in activation energies for cyclohexyl radical addition can be correlated with the C? Cl bond dissociation energies in the adduct radicals. 相似文献
20.
Toshihiro Tominaga Shingo Muraoka Takeshi Ishii Yuroku Yamamoto 《Journal of solution chemistry》1987,16(8):615-624
The solubility of tris(acetylacetonato)cobalt(III) [Co(acac)3] has been measured in aqueous surfactant solutions of sodium decylsulfate (NaDeS), dodecylsulfate (NaDS), and tetradecylsulfate (NaTS), and dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and hexadecyltrimethylammonium bromide (CTAB) at 35°C. The solubility increases in the order DTABTTABCTAB3. The importance of the surface solubilization is suggested. The results are compared with those for other solubilizates. 相似文献