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31.
Qianqian Zhai Zhihua Lu Jing Wang Weina Wang Yudong Ma Caili Yue 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):803-811
AbstractA method of Fourier transform near-infrared (FT-NIR) spectroscopy combined with partial least squares (PLS) model was successfully applied to investigate the hydrolysis kinetics of four kinds of silane coupling agents (phenyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-chloropropyltriethoxysilane) in an acid-catalyzed EtOH system. The fast scanning speed and high sensitivity of the FT-NIR spectroscopy, and the powerful data processing ability of the PLS, enabled the method to quantitatively and accurately catch the fast changing H2O concentration during the hydrolysis processes without delay, realizing the study of the fast-paced hydrolysis reactions of the silane coupling agents. The results showed that electrophilic substitution occurred in the hydrolysis reactions, which followed second-order reactions and greatly depend on the catalyst concentration and reaction temperature. The hydrolysis rate constants, activation energy, and Arrhenius Frequency factors were gained. In conclusion, the FT-NIR PLS model is a powerful tool for hydrolysis kinetics researching of the silane coupling agents. 相似文献
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33.
XIANG VAN ZENG XIANCHENG∗ CHENG SIQING LI YANTUAN XIE JIAQING 《Journal of Dispersion Science and Technology》2013,34(7):857-867
Abstract The hydrolysis of p-nirrophenyl picolinate (PNPP) catalyzed by the Cu(II) and Zn(H) complexes of d-glucosamine schiff base was investigated kinetically by observing the rates of the release of p-nitrophenol in the buffered micellor solution at different pit and 25°C. The scheme for reaction acting mode involving a ternary complex contain ligand, metal ion and substrate in micelle was establish and the reaction mechanisms were discussed The experimental results indicated that the complexes catalyzed efficiently the hydrolysis of PNPP, especially Zn(II) complex. The rate constant kN, which shows the catalytic reactivity of complexes, WBI determined to be 0.4251 s?1 far Cu(II) complex at pH 7 60 in micellar solution. The catalytic reactivity of Zn(II) complex were much larger than Cu(II) complex, the kN was determined to be 3.1914 s?1 at same pH value. 相似文献
34.
《Journal of Dispersion Science and Technology》2013,34(5):683-689
Abstract The effects of two metal complexes of 2,2′‐dipyridylamine (bpya) ligand, [(bpya)Cu]Cl2 and [(bpya)Zn]Cl2, in promoting the hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP) have been kinetically investigated in Brij35 micellar solution and at 298 K, pH ranging from 6.41 to 8.6. In neutral micellar solution at 298 K, pH 7.02, the rate constants for the catalytic hydrolysis of BNPP by [(bpya)Cu]Cl2 and [(bpya)Zn]Cl2 are 1.2 × 106 times and 1.5 × 105 times higher than those for the spontaneous hydrolysis, respectively. Kinetic studies show that the active species in the catalytic hydrolysis of BNPP is the aquo‐hydroxy form, and the relative kinetic and thermodynamic parameters indicate that the mechanism of the reaction involves intramolecular nucleophilic attack on the metal center‐bound diester. 相似文献
35.
Hisham J. Y. El-Aila 《Journal of Dispersion Science and Technology》2013,34(9):1208-1211
In this article, a mononuclear Mn(Niten)2H2O complex was prepared to catalyze hydrolysis of p-nitrophenyl acetate (PNPA) in presence of Cetyltrimethylammonium bromide (CTAB) micellar system in different pH range from 6.5–10 at 25°C. These results obtained indicate that the complex exhibits good catalytic function. It also appears the complex accelerates the hydrolytic cleavage of PNPA in cationic CTAB micellar solution which may be due to coordinating ability of substrate to complex, electrostatic interaction between micelles and complex and due to electrostatic interaction between micelles with reactant. 相似文献
36.
Cécile Zamy Patrick Mazellier 《International journal of environmental analytical chemistry》2013,93(14-15):1059-1068
The hydrolysis of six selected pesticides has been studied in aqueous solution. Four organophosphorus pesticides (disulfoton, isofenfos, isazofos and profenfos) and two N-methylcarbamate derivatives (oxamyl and ethiofencarb) were selected. Hydrolysis was performed in purified buffered water at different pH in the range 7.0–10.0 (ionic strength?=?2.5?mM, T?=?25°C). At pH?=?8.0, isofenfos and disulfoton (t 1/2?≈?4 years, t 1/2?≈?1 year, resp.) were found to be far more stable than isazofos (t 1/2?≈?5 months), ethiofencarb and profenofos (t 1/2<1 month), themselves more stable than oxamyl (t 1/2?≈?1 day). As expected, a strong dependence on pH was observed for all pesticides: the rate of degradation increased when the pH increased. Degradation products were identified by GC–MS and/or LC–MS. Possible structures are presented in the article. 相似文献
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38.
Kathryn M. Kuivila Bryan E. Jennings 《International journal of environmental analytical chemistry》2013,93(13-14):897-911
Temporal patterns of pesticide inputs to San Francisco Bay were identified and correlated with timing of application and transport mechanism. Fluxes were calculated from measured concentrations and estimated flow. Persistence of the pesticides under typical riverine or estuarine conditions were estimated from laboratory experiments. Simazine was detected most frequently and had the highest flux into the Bay, which could be explained by its continuous use and long half-life. In comparison, diazinon was detected at lower concentrations and had a lower flux which corresponded to its lower use and shorter half-life. The order-of-magnitude lower fluxes of carbofuran and methidathion corresponded to their lower use and expected hydrolysis. Molinate was detected at the highest concentration but its flux was lower than expected, considering its very high use and persistence in the laboratory experiments. Additional loss of molinate is likely to occur from volatilization and photodegradation on the rice fields. Although thiobencarb had the second highest use, it had the lowest flux of the six pesticides, which can be attributed to its loss via hydrolysis, photodegradation, volatilization, and sorption to sediments. Fluxes into San Francisco Bay were equal to or greater than those reported for other estuaries, except for the Gulf of Mexico. 相似文献
39.
This work is devoted to the elaboration of a practical scheme for the synthesis of dendritic derivatives of gallic acid containing a carboxylate-ω-alkylphosphonic acid group and three terminal promesogenic substituents. Two synthetic strategies toward the target compounds were examined that differ in the sequence of the introduction of the promesogenic units and ω-alkylphosphonic group. 相似文献
40.
Environmentally benign ionic liquid [bmim]HSO4 was found suitable for conversion of nitriles into carboxylic acids under mild conditions with excellent purity. 相似文献