共查询到20条相似文献,搜索用时 24 毫秒
1.
L. Ya. Zakharova F. G. Valeeva A. R. Ibragimova V. M. Zakharov L. A. Kudryavtseva Yu. G. Elistratova A. R. Mustafina A. I. Konovalov S. N. Shtykov I. V. Bogomolova 《Colloid Journal》2007,69(6):718-725
It is found that a sodium dodecyl sulfate-Brij 35 binary mixture inhibits the alkaline hydrolysis of O-ethyl-O-p-nitrophenylchloromethylphosphonate. Tensiometric data and variations in cloud point suggest the synergistic effect of the above surfactants caused by the formation of mixed micelles. The method of solvatochromic probe E T(30) shows that the micropolarity of a medium rises at the sites of localization of substrates solubilized in micelles with an increase in ionic surfactant fraction in mixed aggregates. Variations in micellization properties, micropolarity, and surface potential with the composition of the binary mixture of the surfactants influence the catalytic properties of mixed micelles with respect to the examined reaction. 相似文献
2.
Avinash Bhadani Sukhprit Singh Raman Kamboj Vinay Chauhan 《Colloid and polymer science》2013,291(10):2289-2297
Linear fatty alcohols on reaction with chloro/bromo acetic acid in the presence of catalytic amount of p-toluene sulphonic acid monohydrate under solvent-free conditions are converted into alkyl-2-haloacetate which on reaction with N-methyl pyrrolidine gives ester-functionalized pyrrolidinium surfactants. Thus, new series of ester-functionalized heterocyclic pyrrolidinium head group containing cationic surfactants have been synthesized by green approach via energy saving and cost effective methodology. These new surfactants have been investigated for their surface properties by surface tension, conductivity, and fluorescence method. Surface properties of these surfactants have been found to be far better compared to conventional heterocyclic cationic surfactants having similar hydrophobic alkyl chain length. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(33):9952-9956
Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity has not been well established. In this study, we employed multiple surface‐sensitive techniques to characterize the surface termination (one aspect of surface reconstruction) of SrTiO3 (STO) after thermal pretreatment (Sr enrichment) and chemical etching (Ti enrichment). We show, by using the conversion of 2‐propanol as a probe reaction, that the surface termination of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivity over a wide range, which is not possible with single‐metal oxides, either SrO or TiO2. Density functional theory (DFT) calculations explain well the selectivity tuning and reaction mechanism on STO with different surface termination. Similar catalytic tunability was also observed on BaZrO3, thus highlighting the generality of the findings of this study. 相似文献
4.
A. B. Mirgorodskaya E. I. Yackevich F. G. Valeeva V. A. Pankratov L. Ya. Zakharova 《Russian Chemical Bulletin》2014,63(1):82-87
Quantitative parameters characterizing the aggregation behavior of dicationic surfactants of the 12-s-12 type in aqueous solutions were determined: critical micelle concentrations, aggregation numbers, and surface potentials. The effects of the spacer length of the surfactants on their solubilizing effect with respect to hydrophobic (dye Orange OT) and water-soluble (p-nitrophenol) spectral probes and on their ability to shift acid-base equilibria were studied. The kinetics of alkaline hydrolysis of p-nitrophenyl acetate and p-nitrophenyl caprinate in 12-s-12 solutions was studied by spectrophotometry. A correlation between the micellar catalytic effect and the surface potential of micelles was established. The pronounced substrate specificity was revealed: the maximum acceleration of hydrolysis is observed in solutions of 12-6-12, attaining 1760 times for p-nitrophenyl caprinate. 相似文献
5.
A. B. Mirgorodskaya L. R. Bogdanova L. A. Kudryavtseva S. S. Lukashenko A. I. Konovalov 《Russian Journal of General Chemistry》2008,78(2):163-170
The surface potential in aqueous micellar solutions of a series of cetyltrialkylammonium bromides containing a hydroxyalkyl fragment in the head group was determined with a spectral probe (p-nitrophenol). It was found that the catalytic effect exerted by these surfactants in solution on the base hydrolysis of carboxylic acid esters is determined by two factors. First, the charged nucleophile is concentrated at the micelle surface. Second, hydrogen bonding of the substrate with the hydroxyalkyl substituents results in its activation. 相似文献
6.
Mahesh M. Kadam 《Journal of Dispersion Science and Technology》2013,34(6):861-868
The influence of hydrophobic chain length in nonionic surfactants on interfacial and thermodynamics properties of a binary anionic‐nonionic mixed surfactant was investigated. In this study, nonionic surfactants lauric‐monoethanolamide (C12 MEA) and myrisitic‐monoethanolamide (C14 MEA) were mixed with an anionic surfactant, α‐olefin sulfonate (AOS). The critical micelle concentration (cmc), maximum surface excess (Γmax), and minimum area per molecule (Amin) were obtained from surface tension isotherms at various temperatures. The thermodynamic parameters of micellization and adsorption were also computed. Micellar aggregation number (Nagg), micropolarity, and binding constant (Ksv) of pure and mixed surfactant system was calculated by fluorescence measurements. Rubingh's method was applied to calculate interaction parameters for the mixed surfactant systems. 相似文献
7.
E. P. Tishkova L. A. Kudryavtseva R. A. Shagidullina B. E. Ivanov 《Russian Chemical Bulletin》1994,43(9):1488-1492
The effect of dicationic surfactants on the hydrolysis of bis(4-nitrophenyl) ethyl phosphate in a borate buffer is studied. The presence of long-chain surfactants results in a significant (up to 50-fold) increase in the observed rate constant (k
obs) of the process. The catalytic effect of micelles increases with increasing alkyl chain length due to the strengthening of binding of the reagents by micelles. The presence of two cationic centers in the surfactant molecule enhances the catalytic properties of micelles. The dependence ofk
obs of hydrolysis of the substrate on the borate buffer concentration is studied. Alkaline hydrolysis is more sensitive to the added surfactant than the reaction involving borate ions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1576–1580, September, 1994. 相似文献
8.
ZENG XIANCHENG LI QILIN WANG QIAN QIN TAMING LI GANZUO HUANG QIZHONG 《Journal of Dispersion Science and Technology》2013,34(7):531-541
The alkaline hydrolysis of aromatic and normal aliphatic acid esters has been studied at 25°C in micellar solutions of surfactants (DTAB, TTAB, CTAB, SDS, Brij 35 and Triton X—100) with UV spectrophotometry and the method of thermokinetics in this paper. The rate constants of the alkaline hydrolysis of esters in micellar pseudophase, k1m and K2m have been calculated, respectively. The ratios of k2m to k2w or k1w to k1w indicate that the alkaline hydrolysis of esters arc inhibited by all of the surfactants investigated. It was supposed that such inhibition is mostly in relation to the micropolarity of micellar surface. The critical micellar concentrations of the corresponding systems have also been measured with the conductivity method and UV spectrophometry in this paper. 相似文献
9.
Alkali catalytic hydrolysis of poly(vinyl acetate) (PVAc) grafting onto polyurethane film surface was a heterogeneous reaction. The hydrolysis was carried on the PVAc particle surface, and the concentration of the alkali in the system was tested by titration method. The kinetics of PVAc surface hydrolytic reaction was studied by simple second-order reaction model. From linear regression analysis of experimental data, we inferred that the activation energy (E a ) and pre-exponential factor (A) of PVAc surface hydrolytic reaction were 70.7 ± 0.2 kJ mol?1 and (5.7 ± 0.5) × 1012 kg mol?1 s?1, respectively. The results of transmission electron microscopy stated that the apparent hydrolytic degree was 2.1% when the surface of PVAc particle hydrolyzed absolutely. 相似文献
10.
A series of bis-sulfosuccinate anionic gemini surfactants were synthesized from meristyl alcohol (BSGSMA1,4; BSGSMA1,6, and BSGSMA1,8) containing 4, 6, and 8 methylene chains as different flexible spacer lengths. The chemical structures of synthesized geminis were confirmed by using spectroscopic analytical techniques, viz., elemental analysis, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy(NMR). Investigations were carried out to examine the effect of different spacer length and different salts (organic and inorganic) on surface and fluorescence properties of prepared gemini surfactants. The results of surface properties shown that surface tension at CMC (?CMC) and critical micelle concentration (CMC) were reduced and pC20 value was enhanced with increased spacer length. Fluorescence investigations were also revealed the significance of longer spacer with the concluded remarks of higher aggregation number and reduced micropolarity for BSGSMA1,8 having elongated flexible spacer. The results of salts studies had shown the better results for organic salts as compared to inorganic salts. 相似文献
11.
12.
Jijing Shen Zhenguo Zhao∗ Jiming Ma 《Journal of Dispersion Science and Technology》2013,34(7):883-897
Micellar catalysis by nine cationic surfactants of the basic hydrolysis of 2,4-dinitrochlorobenzene(DNCB) was studied. The results obtained are as follows: (I) The second-order constants k2 for the hydrolysis reaction of DNCB catalized by the cationic micelles increase by a factor of 11–100 than that in water. Plots of k2 against the surfactant concentration show an S-type curve, and the catalytic effect is observed below the critical micelle concentration(CMC) of the surfactants. (2) For a series of surfactants, there is an optimal chain length for the alkyl of the surfactants to show the greatest catalytic effect. (3) The hydrolysis rate of DNCB decreases as the base concentration increases. (4) For the surfactants with the same hydrophilic and hydrophobic groups, chlorides have advantage over bromides in enhancing the reaction rate. These results can be interpreted in term of the changes in CMC, micelle size, solubilization capacity of the micelles, binding degree of counterion et al. 相似文献
13.
The hydrolysis of bis(p‐nitrophenyl)phosphate (BNPP) catalyzed by N‐methyldiethanolamine‐Ce(III) complex in the presence and absence of cetyltrimethylammonium bromide (CTAB) and Brij35 surfactants at pH 7.20 and 303 K has been studied. The experimental results indicate that N‐methyldiethanolamine‐Ce(III) complex remarkably accelerates the hydrolysis of BNPP. The observed first‐order rate constant of the hydrolysis of BNPP catalyzed by N‐methyldiethanolamine‐Ce(III) complex at pH 7.20 and 303 K is 1.22 × 10?2 s?1, which is 1.09 × 109 times of that of spontaneous hydrolysis of BNPP at pH 7. It is close to the activity of natural enzyme. A general quantitative treatment of the catalytic reaction involved a ternary complex as MmLlS has also been proposed in this paper. Applying this method to the catalytic hydrolysis of BNPP, we have obtained its thermodynamic and kinetic parameters. CTAB and Brij35 surfactant micelles obviously influence the rate constants of the catalytic hydrolysis of BNPP. Brij35 micelles promote the catalytic hydrolysis of BNPP, while CTAB micelles inhibit it. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 687–692, 2004 相似文献
14.
A. B. Mirgorodskaya L. Ya. Zakharova F. G. Valeeva A. V. Zakharov L. Z. Rizvanova L. A. Kudryavtseva H. E. Harlampidi A. I. Konovalov 《Russian Chemical Bulletin》2007,56(10):2000-2007
The variation of the microscopic properties (surface potential, micropolarity, etc.) of the interface of cetyltrimethylammonium bromide micelles upon the addition of a background electrolyte or the nonionic
surfactant Triton X-100 decreases the rates of ion-molecular reactions, namely, alkaline hydrolysis of carboxylic acid esters
and tetracoordinate phosphorus acid esters, and results in the shift of acid-base equilibria.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1933–1940, October, 2007. 相似文献
15.
利用荧光探针法和表面张力法测定了新型双子型阳离子表面活性剂的临界胶团浓度(cmc)、最低表面张力(γcmc)、胶团微极性和胶团聚集数(Nagg),探讨了连接基团对此类表面活性剂在水溶液中聚集行为的影响.结果表明,当连接基团增长时,cmc和胶团微极性增加,γcmc增大,Nagg减少,表面活性降低,在溶液中自发形成胶团的能力减弱. 相似文献
16.
The article describes preparation of new calixarene biopolymers consisting of the immobilization of convenience calixarene derivative onto cellulose and chitosan biopolymers, and the encapsulation of these calixarene biopolymers with Candida rugosa lipase within a chemical inert sol–gel supported by polycondensation with tetraethoxysilane and octyltriethoxysilane. The catalytic properties of immobilized lipase were evaluated into model reactions employing the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of naproxen methyl esters from racemic prodrugs in aqueous buffer solution/isooctane reaction system. The resolution studies using sol–gel support have observed more improvement in the enantioselectivity of naproxen E?=?300 with Cel-Calix-E than with encapsulated lipase without calixarene-based materials. Furthermore, the encapsulated lipase (Cel-Calix-E) was still retained about 39 % of their conversion ratios after the fifth reuse in the enantioselective reaction. 相似文献
17.
L. Ya. Zakharova F. G. Valeeva A. V. Zakharov A. B. Mirgorodskaya L. A. Kudryavtseva A. I. Konovalov 《Kinetics and Catalysis》2007,48(2):221-227
The aggregation properties and catalytic effect of the cetyltrimethylammonium bromide-Triton X-100 binary system in nucleophilic substitution in esters of phosphorus acids are studied in the region of normal micelles and oil/water microemulsions. In the presence of phenol, the dissociation of O-alkyl-O-para-nitrophenyl chloromethyl phosphonates is up to 200 times more rapid than the same reaction in water. The efficiency of catalysis depends on the molar ratio of the surfactants and is determined by several factors: concentration, changes in the microenvironment of the reactants, and the shift of the pK a of phenol. 相似文献
18.
ZENG XIANCI-IENG MENG XIANGGUANG WANG QIAN ZHANG YUANQIN QIN ZIMING 《Journal of Dispersion Science and Technology》2013,34(4):369-378
The alkaline hydrolysis of dimethylformamide has been studied at 40'C in micellar solutions of single surfactant (CTAB. SDS. Brij 35) with the analog thermoanalytical curve method of thermokinetics. A kinetic equation of micellar catalysis under the condition of highter reactant concentration than micellar concentration ([S]>[M]) has been derived from the pseudophase model of micellar catalysis and some relative assumptions, The kinetic parameters. km, k2mand the association constant of reactant with micelle K1, have been calculated in this way. the results indicate that these surfactant micelles exhibit catalytic effect on the reaction. This is attributed to the micropolarity and local concentration effect of micelles. 相似文献
19.
E. L. Vecherkina S. K. Kudaikulova R. M. Iskakov B. A. Zhubanov V. Voitekunas J. M. Abadie 《Polymer Science Series A》2007,49(2):142-147
The formation of metallized polyimide films in situ, namely, the alkaline hydrolysis of film surfaces, chelation of the modified surface with metal ions, and their chemical reduction giving rise to a metal layer, has been investigated. Initial polyimide films are cast from reaction solutions on a glass substrate. The solutions are prepared through the polycondensation of dianhydride of tricyclo[4.2.2.02.5dec-7-ene-3,4,9,10-tetracarboxylic acid and 4,41-diaminodiphenyl oxide in N-methyl-2-pyrrolidone at 160°C. It has been shown that alkaline water-alcohol solutions are optimal media for the hydrolysis of the film surface. The maximal exchange of alkali metal ions is achieved through formation of a more stable metal-ligand complex of poly(amido acid), with the chelation rate depending on the nature of a metal. The metal reduction proceeds rapidly; however, the mechanism of this process depends on the pH of a medium. The annealing of metallized films results in the imidization of poly(amido acid) and in the growth of metal grains on the material surface to yield a metal layer with good optical properties and high conductivity. 相似文献
20.
L. Ya. Zakharova F. G. Valeeva R. A. Shagidullina L. A. Kudryavtseva 《Russian Chemical Bulletin》2000,49(8):1360-1364
The catalytic effect of the sodium dodecyl sulfate-hexanol-water ternary reverse micellar system in the alkaline hydrolysis
ofO-alkylO′-aryl chloromethylphosphonates as a function of the substrate structure was studied. The micellar effect is mainly determined
by a change in the electronic properties of the substituents, while the hydrophobicity plays a secondary role. The kinetic
data were examined in the framework of the pseudo-phase model of micellar catalysis. The rate constants of the reaction in
the surface layer and the partition constants of the reactants were calculated.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1366–1370., August, 2000. 相似文献