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101.
102.
Laura M. Bruno José L. de Lima Filho Eduardo H. de M. Melo Heizir F. de Castro 《Applied biochemistry and biotechnology》2004,113(1-3):189-199
Mucor miehei lipase was immobilized on magnetic polysiloxane-polyvinyl alcohol particles by covalent binding with high activity recovered.
The performance of the resulting immobilized biocatalyst was evaluated in the synthesis of flavor esters using heptane as
solvent. The impact on reaction rate was determined for enzyme concentration, molar ratio of the reactants, carbon chain length
of the reactants, and alcohol structure. Ester synthesis was maximized for substrates containing excess acyl donor and lipase
loading of 25 mg/mL. The biocatalyst selectivity for the carbon chain length was found to be different concerning the organic
acids and alcohols. High reaction rates were achieved for organic acids with 8 or 10 carbons, whereas increasing the alcohol
carbon chain length from 4 to 8 carbons gave much lower esterification yields. Optimal reaction rate was determined for the
synthesis of butyl caprylate (12 carbons). Esterification performance was also dependent on the alcohol structure, with maximum
activity occurring for primary alcohol. Secondary and tertiary alcohols decreased the reaction rates by more than 40%. 相似文献
103.
Winghong Chan Suei Yee Lam-Leung Chingfai Ng Junqi Ding Shiping Xi 《Journal of polymer science. Part A, Polymer chemistry》1995,33(15):2525-2531
New diamino monomers IIa – IIg were synthesized in a two-step reaction sequence starting from p-acetamidobenzenesulfonyl chloride. Solution polymerization of these monomers in DMAC with terephthaloyl or isophthaloyl chloride resulted in the formation of a series of 14 poly(amide sulfonamide)s (PASAs) in excellent yield (> 95%). The polymers have in-trinsic viscosities of 0.32–1.11 dL g?1. Except for polymers IIIa ? p and IIId - p , all other PASAs were readily soluble in aprotic polar solvents including DMAC, DMF, and DMSO. Thermogravimetric analyses of the polymers showed moderate thermal stability with 10% weight loss being recorded in the range of 325–408°C. In addition, these polymers exhibit moderate chemical stabilities toward alkali, acidic, and chromic acid solution. © 1995 John Wiley & Sons, Inc. 相似文献
104.
Some new pyridyl alcohols with the cis-bicyclo[3.3.0]octane scaffold were synthesized and used as chiral ligands for the enantioselective addition of diethylzinc to aldehydes. Ligands 4 were found to be far superior to the C2-symmetric ligands 2 in terms of enantioselectivities. Quantitative yields and enantiomeric excesses of up to 92% were obtained when the ligand 4 was used. The carbonyl function in 4 proved to be beneficial for the high enantioselectivities in the addition of diethylzinc to aldehydes. Conversion of the carbonyl group into oxime or oxime ether group led to a sort of more active ligands, which catalyzed the same reaction with rate acceleration. 相似文献
105.
Copper mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative smoothly proceeded to give the corresponding 2-alkylated 4-fluoro-5-hydroxyhomoallylic alcohol derivative with completely Z and 2,5-syn selective manner. Regio- and stereoselective conversion of the C5-hydroxyl group of the fluoroolefin thus obtained to amino group could be achieved through one-pot mesylation and azidation reaction. 相似文献
106.
基于支持向量机的羰基化合物红外光谱研究 总被引:1,自引:0,他引:1
设计了一个4层分等级分类系统,通过支持向量机技术对羰基化合物的红外光谱成功地进行了信息分类和提取,并与人工神经网络进行比较,结果表明:支持向量机对羰基类化合物红外光谱分类效果优于人工神经网络;另外详细探讨了表征酰胺类化合物的特征光谱峰片段对识圳伯仲叔酰胺的影响,证明了酰胺的N-H伸缩振动峰对识别伯仲叔酰胺贡献最大,为构建红外光谱智能解析系统提供了定量依据。 相似文献
107.
Preparation of Silver Nanoparticles through Alcohol Reduction with Organoalkoxysilanes 总被引:1,自引:0,他引:1
Hoe Jin Hah Sang Man Koo Sang Hoon Lee 《Journal of Sol-Gel Science and Technology》2003,26(1-3):467-471
Silver nanoparticles of narrow size distribution were prepared through the chemical reduction in an alcohol solution with several organoalkoxysilanes. In this system, organoalkoxysilanes served as a stabilizer, protecting silver nanoparticles from aggregation. The changes in size and morphology of colloidal silver nanoparticles were investigated with the addition of organoalkoxysilanes such as 3-aminopropyltriethoxysilane (APS), methyltriethoxysilane (MTS), phenyltrimethoxysilane (PTS), vinyltriethoxysilane (VTS), and 3-glycidoxypropyltrimethoxysilane (GPS) as stabilizers. The organic functional groups of organoalkoxysilanes interact with silver ions and clusters, which stabilize silver nanoparticles in the system. The silver nanoparticles obtained were characterized with transmission electron microscopy (TEM), UV-vis spectroscopy, etc. 相似文献
108.
109.
Three highly sensitive spectrophotometric methods for the determination of platinum(IV) have been developed, based on its colour reactions with molybdate and basic dyes (BD) in aqueous solution in the presence of poly(vinyl alcohol). Platinum(IV) reacts with molybdate and BD to form ion — association complexes of composition (BD)2[Pt (MoO4)3]. The molar absorptivities are between 6.83 × 105 and 9.51 × 105 dm3mol–1cm–1, the highest value being found with nile blue. Suitable conditions for the reactions and the effects of foreign ions were investigated. The methods can be applied to the spectrophotometric determination of trace amounts of platinum(IV) in some catalysts and ores. 相似文献
110.
在酸性介质中用氧化还原滴定法研究了铈(IV)离子在痕量铱(III)离子催化作用下,于298~313 K区间氧化四氢糠醇(THFA)的反应动力学. 结果表明,反应对铈(IV)离子为一级,对铱(III)离子也为一级,对四氢糠醇的表观反应级数为正分数. 准一级速率常数kobs随[H+]增加而增大,而随[HSO4-]增加而减小. 在氮气保护下,反应能引发丙烯腈聚合,说明在反应中有自由基产生. 通过kobs与[HSO4-]的依赖关系,找到本反应体系的动力学活性物种是Ce(SO4)2,并计算出平衡常数,速控步骤的速率常数及相应的活化参数. 相似文献