The Studies of Microwave Effects on the Chemical Reactions

Microwave heating involves direct absorption of energy by functional groups that bear ionic conductivity or a dipole rotational-effect, and this energy is then released into the surrounding solution. This absorption of energy causes the functional groups involved to have higher reactivity to other surrounding reactants than when they are simply incubated with the reactants at the same temperature. In other word the enhanced rate of the reaction can be due to the reactant stirred by the molecular dipole rotation and molecules themselves acting as a stirring bar. In contrast to conventional heating, the salient feature of “dipole rotation” constitutes one efficient form of “molecular agitation” or “molecular stirring” many aspects of which can be explore in chemical reactions. We will discuss some of the useful applications of this “molecular agitation” by means of microwave irradiation. Using this unique technology, we have developed: 1) a method to control the cleavage sites of peptide bonds, especially those bonds connected to aspartic acid residues inside the native peptides and proteins, 2) a method to increase coupling efficiency in solid-phase peptide synthesis using a common microwave oven, 3) a novel procedure that increases the rate of alcalase-catalyzed reactions using microwave irradiation in peptide-bond formation with proline as a nucleophile and selective benzoylation of a pyranoside derivative, 4) a procedure to solubilize and hydrolyze retrograded starch, 5) a novel procedure to enhance the rate of saponification in a serum sample for very long chain fatty acid analysis.     

Investigations on the stability of bendamustin, a cytostatic agent of the nitrogen mustard type, I. Synthesis, isolation, and characterization of reference substances

Summary The following compounds were chosen as reference substances for HPLC investigations on 4-(6-bis(2-chloro-ethyl)amino-3-methylbenzimidazoyl(2))butyric acid (bendamustin), an antineoplastic agent of the N-lost type (synthesized or isolated from crude bendamustin): 4-(6-((2-chloroethyl)(2-hydroxyethyl)amino)-3-methylbenzimidazoyl(2))butyric acid (HP1), 4-(6-bis(2-hydroxyethyl)amino-3-methylbenzimidazoyl(2))butyric acid (HP2), ethyl-4-(6-bis(2-hydroxyethyl)amino-3-methylbenzimidazoyl(2))butyrate (dihydroxyester), and ethyl-4-(6-bis(2-chloroethyl)amino-3-methylbenzimidazoyl(2))butyrate (dichloroester). Furthermore, the so far unidentified side product 4-(7,8-dihydro-6-(2-chloroethylamino)-3-methyl-1,4-thiazino[3,2-g]benzimidazoyl(2))-butyric acid (NP1), formed in the last step of the synthesis, was isolated and identified.

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Untersuchungen zur Stabilität von Bendamustin, einem Cytostatikum vom N-Lost-Typ, 1. Mitt.: Synthese, Isolierung und Charakterisierung von Vergleichssubstanzen

Zusammenfassung Die folgenden Verbindungen wurden als Vergleichssubstanzen für HPLC-analytische Untersuchungen von 4-(6-Bis(2-chlorethyl)amino-3-methylbenzimidazoyl(2))buttersäure (Bendamustin), einem Antitumormittel des N-lost-Typs, synthetisiert oder aus Bendamustin-Rohstoff vor der Endreinigung isoliert: (4-(6-((2-Chlorethyl)(2-hydroxyethyl)amino)-3-methylbenzimidazoyl(2))buttersäure (HP1), 4-(6-Bis(2-hydroxyethyl)amino-3-methylbenzimidazoyl(2))buttersäure (HP2), 4-(6-Bis(2-hydroxyethyl)amino-3-methylbenzimidazoyl(2))buttersäureethylester (Dichlorester). Weiterhin konnte das bislang unbekannte Nebenprodukt 4-(7,8-Dihydro-6-(2-chlorethylamino)-3-methyl-1,4-thiazino[3,2-g]benzimidazoyl(2))buttersäure (NP1), welches sich im letzten Schritt der Synthese bildet, isoliert und identifiziert werden.

     

不同液体环境下聚丙烯酰胺的单分子力学

利用单分子力谱研究了非离子型聚丙烯酰胺(NPAM)及其水解产物阴离子型聚丙烯酰胺(APAM)在不同液体环境下的单链弹性. 利用改进的自由连接链(M-FJC)模型中的单链弹性模量参数(K₀)描述NPAM在不同pH值水溶液中的单链弹性. 实验结果表明, K₀随着溶液pH值增加而增大, 表明NPAM在碱性溶液中的水解度具有pH依赖性. 由于K₀和高分子链的净电荷正相关, K₀增大表明NPAM链净电荷增多, 结构单元之间的静电排斥作用增强使高分子链呈现高度伸展的构象. 在此基础上研究了APAM在不同pH值溶液中的构象, 单分子力谱数据表明, APAM在酸性水溶液中为柔性链, 在碱性水溶液中呈现较伸展的构象, 从而在分子水平上阐明APAM链构建的水凝胶网络的溶胀机理. 单分子层面的深入研究有望阐明这类高分子的减阻机理.     

Transformation of benzonitrile into benzyl alcohol and benzoate esters in supercritical alcohols

The reactions of benzonitrile in supercritical methanol, ethanol, and 2-propanol were investigated under non-catalytic conditions. In supercritical methanol, benzonitrile was converted to methyl benzoate in high yield. The esterification reaction also occurred in supercritical ethanol to afford ethyl benzoate in moderate yield. The esterification could occur via a route analogous to the Pinner reaction. On the other hand, benzonitrile in supercritical 2-propanol yielded no ester. Benzyl alcohol was the major product in supercritical 2-propanol. We investigated the reaction of the CN bond in supercritical 2-propanol. In supercritical 2-propanol, N-benzylideneaniline was transferred to the reduction product (N-benzylaniline) and hydrolysis products (benzyl alcohol and aniline). The hydrolysis reaction was restricted when the reaction was carried out in supercritical 2-propanol with a low water content. This indicates that the water in the 2-propanol acts as a reagent for the hydrolysis of the CN bond. These results suggested the following reaction process: C₆H₅CN→C₆H₅CHNH→C₆H₅CHO→C₆H₅CH₂OH.     

Hydrolysis of Ammonia-pretreated Sugar Cane Bagasse with Cellulase, β-Glucosidase, and Hemicellulase Preparations

Sugar cane bagasse consists of hemicellulose (24%) and cellulose (38%), and bioconversion of both fractions to ethanol should be considered for a viable process. We have evaluated the hydrolysis of pretreated bagasse with combinations of cellulase, β-glucosidase, and hemicellulase. Ground bagasse was pretreated either by the AFEX process (2NH₃: 1 biomass, 100 °C, 30 min) or with NH₄OH (0.5 g NH₄OH of a 28% [v/v] per gram dry biomass; 160 °C, 60 min), and composition analysis showed that the glucan and xylan fractions remained largely intact. The enzyme activities of four commercial xylanase preparations and supernatants of four laboratory-grown fungi were determined and evaluated for their ability to boost xylan hydrolysis when added to cellulase and β-glucosidase (10 filter paper units [FPU]: 20 cellobiase units [CBU]/g glucan). At 1% glucan loading, the commercial enzyme preparations (added at 10% or 50% levels of total protein in the enzyme preparations) boosted xylan and glucan hydrolysis in both pretreated bagasse samples. Xylanase addition at 10% protein level also improved hydrolysis of xylan and glucan fractions up to 10% glucan loading (28% solids loading). Significant xylanase activity in enzyme cocktails appears to be required for improving hydrolysis of both glucan and xylan fractions of ammonia pretreated sugar cane bagasse.     

F/Cl mediated microwave assisted breakdown of cellulose to glucose

Microwave irradiation of aqueous solution of cellulose in the presence of NaF/NaCl resulted into disintegration of cellulose to its monomeric unit, glucose (55%) in 20 min.     

特殊盐效应对水解反应催化常数测定的影响

以苯甲醛缩二叔丁醇(BDTB)、原苯甲酸三乙酯(TEDB)和N-(p-甲氧基亚苄基)吡咯烷鎓离子(MOBP)为底物, 研究了在各种条件下, 用不同盐维持离子强度对水解反应的酸碱催化常数测定的影响。结果表明: 当离子强度低, 溶剂为水或以水为主要组份的混合溶剂时, 判断特殊和普通酸碱催化及测定普通催化常数的标准方法可不受特殊盐效应的干扰。     

Titanium compounds as coatings on polystyrene latices and as hollow spheres

Sub-micron-sized anionic polystyrene latices have been coated with uniform layers of amorphous titanium dioxide by hydrolysis of titanium tetrabutoxide in ethanolic solutions containing the polymer cores. The thickness of the coating layer could be altered by adjusting the concentration of titanium tetrabutoxide and the amount of polymer latex added to the system. Hollow colloidal spheres of crystal titanium dioxide were obtained by calcination of the so-coated polystyrene latices at an elevated temperature. Received: 29 July 1999/Accepted in revised form: 15 October 1999     

Dipeptide-assisted growth of uniform gallium oxohydroxide spindles

The catalytic dipeptide His–Ser was used as an additive in mineralizing gallium ions to form GaOOH, a solid precursor of Ga₂O₃. This dipeptide was chosen to mimic the enzyme structure of silicatein, similar to the well-known catalytic triad of chymotrypsin. The dipeptide promoted formation of spindle-structured GaOOH under acidic conditions by behaving as a heterogeneous nucleation seed. In contrast, no well-defined, structured gallium species were produced in the absence of dipeptide. The catalytic function of the dipeptide was most pronounced at pH values in the range 3–5, which are lower than the pKa of imidazole in the His side chain. These results suggest that the catalytic role of dipeptide influences the gallium hydroxide conversion and growth. This study suggests that a designed peptide with active functionality can be further exploited to produce inorganic compounds with controlled nucleation and growth.