A novel synthesis method for cyclodextrins from maltose in water-organic solvent systems

A novel enzymatic synthesis method of cyclodextrin (CD) from low-mol-wt maltose using cyclomaltodextrin glucanotransferase (CGTase) fromBacillus macerans has been developed in various water-organic solvent systems. A Β-CD was synthesized in a two-phase system consisting of water and cyclohexane. However, no CDs could be synthesized in an aqueous buffer solution. A maximal yield of Β- CD has been obtained at a cyclohexane content volume of 44%. This synthesis has been obtained only at low temperatures, i.e., 7‡C, and did not take place at 50‡C. In addition, various organic solvents have been used for the enzymatic synthesis of CD from maltose. Consequently, Β-CD could be synthesized in various water-organic solvent systems, e.g., cyclohexane, benzene, xylene, and chloroform, but no enzymatic reaction occurred using aliphaticn-hydrocarbon solvents such as hexane, dodecane, and hexadecane. Furthermore, α- and Β- CD could be synthesized in water mixture solutions using organic solvents having an alcoholic group (e.g., ethanol, propanol, butanol, and pentanol) in a wide range of the reaction temperatures, typically 7–50‡C. In this temperature range, α- and Β-CD were also formed and the maximal yield from maltose to Β-CD of approx 13% was reached in 60 h.     

Enthalpies of mixing of isopropyl ether with cyclohexane,benzene, toluene,ethylbenzene, p-xylene and mesitylene at 27°C

Enthalpies of mixing of isopropyl ether with cyclohexane, benzene, mesitylene, ethylbenzene, toluene and p-xylene were determined at 27°C and were found to decrease in the same order as the second components listed. The results are compared with Flory's state theory.     

Kinetics of Conversions of Peroxynitrous Acid in Reactions of Isomerization,Decomposition, and Reduction by Cyclohexane

We have studied the kinetics of decomposition and reduction of peroxynitrous acid HOONO by cyclohexane in aqueous solutions. We used the measured effective rate constants of the reactions to compare the reactivities of the acid in the processes of isomerization, decomposition, and reduction.     

Temperature Function of Birefringence and Structural Changes in Carbazole Crystal

With a modified quarter-wave Sénarmont compensator, exact measurements of the optical path difference have been carried out in (010) plates of carbazole, C₁₂H₉N, in the temperature range 20 < T < 190°C. At a temperature near 155°C distinct anomaly has been found corresponding to crystal-to-crystal phase transformation. The birefringence changes are discussed in terms of temperature dependence of density and orientation of molecules in the unit cell due to thermal expansion of the crystal.     

非除氧条件下6-溴萘硫酸钾超分子组合室温燐光

极少量环己烷存在下 ,由于超分子化合物 β CD BNS 环己烷的形成 ,不经除氧可观察到强的室温光(RTP)发射。同时 ,对影响超分子化合物发光性质的各种因素如形成三元包合物、空间匹配效应、客体分子的结构以及醇和体系中其它组分的相互作用作了详细的讨论     

金属取代型AlPO-5分子筛催化剂上环己烷亚硝化一步法合成己内酰胺(英文)

采用水热法制备了一系列结晶态的AlPO-5(磷酸铝分子筛),SAPO-5(硅磷酸铝分子筛)和MeAlPOs(金属取代型磷酸铝分子筛)催化剂,利用X射线衍射、N2吸附脱附法、扫描电镜、粒度分布、电感耦合等离子光谱、红外光谱、NH3程序升温脱附、H2程序升温还原和热重-微分热重分析对催化剂进行了表征,并考察了其催化环己烷亚硝化一步法制备己内酰胺的反应活性.结果表明,随着Si或金属原子引入AlPO-5结构中,催化剂的Lewis弱酸中心增加,同时出现了Brnsted强酸中心.相对于AlPO-5,具有较大比表面积和较多酸中心的SAPO-5和CrAPO-5表现出较好的环己烷亚硝化反应活性,后者环己烷转化率为8.16%,己内酰胺选择性达68.17%.     

Standard molar enthalpies,volumes, and heat capacities of adamantane in cyclohexane,n-hexane,and carbon tetrachloride. Interpretation using the scaled-particle theory

The volumes, heat capacities, and enthalpies of solution of adamantane in cycloxane,n-hexane, and carbon tetrachloride have been measured as a function of concentration at 25°C (15, 25, and 35°C for the volumes). The results extrapolated to infinite dilution have been resolved into cavity formation and interaction terms. The former have been calculated from the equations of the scaled-particle theory. To estimate the contribution from the latter, we have assumed some proportionality between adamantane-solvent and cyclohexane-solvent interactions. This assumption has been verified with the three different solvents for the three studied thermodynamic functions. The diameter of adamantane in solution has been determined to be 6.36 Å.     

Apparent molar volumes and expansibilities of 1-octanol, 1-nonanol,and 1-decanol in dilute cyclohexane solutions

The densities of solutions of 1-octanol, 1-nonanol, and 1-decanol in cyclohexane up to concentrations of 1.56 mol kg^–1 were measured at temperatures between 20 and 60°C. The apparent molar volumes and expansibilities were found to be linearly dependent on solute concentration. The excess molar volume and the excess thermal expansion coefficient of the solute were derived from the partial molar volume of the solute at infinite dilution and the solute densities. In addition, the limiting partial molar volume of the solute is discussed in terms of the scaled particle theory.     

Effects of the Presence of Cyclohexane or Methylcyclohexane on the Densities and Volumetric Properties of the Mixture (Benzene + Propionitrile)

Excess molar volumes, V_m^E, have been obtained as a function of composition for ternary-pseudobinary mixtures of [(benzene + cyclohexane or methylcyclohexane) + (propionitrile + cyclohexane or methylcyclohexane)] from the densities measured by means of a vibrating-tube densimeter at atmospheric pressure and a temperature of 298.15 K. The values of V_m^E have been correlated using the Redlich–Kister equation to estimate the coefficients and standard errors. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, cyclohexane or methylcyclohexane, has a significant effect on the interaction between benzene and propionitrile.     

Liquid Solution Densities of Ternary-Pseudobinary Mixtures of (Benzene + Cyclohexane) in the Presence of Tetrachloromethane or <Emphasis Type="Italic">n</Emphasis>-Hexane

Densities have been obtained as a function of composition for ternary-pseudobinary mixtures of [(benzene + tetrachloromethane or n-hexane) + (cyclohexane + tetrachloromethane or n-hexane)] at atmospheric pressure and the temperature 298.15 K, by means of a vibrating-tube densimeter. Excess molar volumes, V_m^E, partial molar volumes and excess partial molar volumes were calculated from the density data. The values of V_m^E have been correlated using the Redlich–Kister equation and the coefficients and standard errors were estimated. The experimental and calculated quantities are used to discuss the mixing behavior of the components. The results show that the third component, CCl₄ or n-C₆H₁₄, have quite different influences on the volumetric properties of binary liquid mixtures of benzene with cyclohexane.