Description of the turbidity measurements near the phase transition temperature of poly(N-isopropyl acrylamide) copolymers: the effect of pH, concentration, hydrophilic and hydrophobic content on the turbidity

Absorbance values between 300 and 800 nm of aqueous solutions of poly(N-isopropyl acrylamide-co-itaconic acid-9.80), poly(N-isopropyl acrylamide-co-itaconic acid-52.05) and poly(N-isopropyl acrylamide)s containing Tegomer H-Si 2111 end groups and/or blocks were measured using a Shimadzu 160-A UV-visible spectrometer. Turbidities obtained from these absorbance values were used to interpret the macromolecular phase transition from a hydrophilic to a hydrophobic structure of the polymers. The effects of comonomer type and content, concentration of the solutions, pH and temperature on the coil-globule transition were discussed in terms of turbidity form factor, β related to size and shapes of particles and calculated by using the simplified form of Debye equation.The results presented in this work show that the presence of Tegomer H-Si 2111 (Si containing end groups and/or blocks) or high amount of itaconic acid (IA) in the chains prevent a collapse transition from hydrated extended coils to hydrophobic globules, which aggregate and form a separate phase (β<2). Furthermore, it was observed that in the case of concentrated solutions intermolecular hydrophobic interactions between isopropyl groups overcame the repulsive forces resulting from the ionized carboxylic acid groups of IA or surface active nature of Si containing hydrophobic groups (β>2). This stage of the transition corresponds to macroscopic phase separation after an intramolecular process.     

5－（4－乙酰氧基苯基），10，15，20－三苯基卟啉金属配合物修饰的铂支撑双层脂膜的IV性质

合成并表征了５－（４－乙酰氧基苯基），１０，１５，２０－三苯基卟啉及其金属配合物，将它们作为修饰物，制得铂支撑的双层脂膜，用循环伏安法研究了抗坏血酸的氧化还原反应，并对其机理作了探讨。     

Electrogenerated Chemiluminescence Based on Tris(2,2′-bipyridyl) Ruthenium(II) with Hydroxyl Carboxylic Acid

Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)²⁺₃] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and -gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)³⁺₃below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)²⁺₃*. The factors which affect the determination and HPLC separation of the four acids were also investigated.     

Comprehensive DFT and MO studies on glyoxilic acid oxime and related ions in gas phase and solution: Conformations,basicities and acidities

Density functional (BLYP, B3LYP and BHLYP) and highly correlated MP2 and CCSD(T) calculations have been performed to investigate conformers, energy barriers, intramolecular H-bond strength, gas-phase basicity and deprotonation energies of glyoxilic acid oxime (gao) and related ions in gas phase and in aqueous solution (SCRF-PCM method). BHLYP/6-311G(d,p) and B3LYP/6-31++G(d) predictions for the global minimum conformer of gao were consistent with experiment. BLYP level overestimated the H-bond and stabilized incorrectly the H-bonded conformer. The calculations in solution indicated destabilization of H-bonded conformers due to the small polarizability and weaken of the H-bond. The same global minimum structures in gas phase and aqueous solution were found for gao-neutral (ectt) and gao-dianion (e⁻²), whereas they were different for gao-anion because of the strong decrease of the conformational energies in solution. The global minimum structures of the neutral, anion and dianion of gao, obtained in solution, are in agreement with experiment. The gas-phase basicity (GB) and molecular electrostatic potential (MEP) calculations revealed the same sites for electrophilic attack, supported by the nature of HOMO: the carbonylic oxygen for the neutral, the carboxylic oxygen for the anion and the oxime nitrogen for the dianion. MEP results in gas phase and in solution suggested a region between the two atoms, but not on one atom in accordance with bidentate binding of gao ions to a metal. The BHLYP/6-31++G(d,p) molecular properties of gao were in best consistent with CCSD(T) results. The thermodynamical properties (GB and bond deprotonation energy) of gao were better estimated at B3LYP level.     

Synthesis of diterpene glycosides

Summary Mono-, di-, and linear triglycosides of a diterpene alcohol, derived from abietic acid and glucose have been synthesized employing peracetylbromo--D-glucose (4) and maltose derivatives5 and8 as glycosyl donors. The triglycoside14 exhibits slight haemolytic activity.

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Synthese von Diterpenglycosiden

Zusammenfassung Es wird die Synthese von Mono-, Di-, und linearen Triglycosiden aus einem von Abietinsäure abgeleiteten Diterpenalkohol beschrieben. Als Glycosyldonoren wurden neben Peracetobrom--D-glucose (4) die Maltosederivate5 und8 verwendet. Das Triglycosid14 zeigt schwache hämolytische Aktivität.

     

Reactions of monothiooxamides with O-methylhydroxylamine

The reactions of monothiooxamides with O-methylhydroxylamine were studied. Depending on the substituents in monothiooxamides, the reactions result in the formation of hydroxamic acid derivatives or various N-methoxy derivatives of amidoximes.     

Reactions with Addition Compounds Containing Activated Formic Acid

Addition compounds of formic acid with tertiary organic bases in ratios higher than that required for salt formation (3:1 and 2:1 adducts) contain formic acid in a highly activated form. In particular, the 3:1 adducts of formic acid with trimethylamine and triethylamine are liquid reducing agents that are convenient to handle and are suitable for use in many selective reductions. These addition compounds have a surprisingly strong reducing action on sulfur dioxide, which is rapidly converted, even at low concentrations, into crystalline rhombic sulfur. Sulfones and polysulfones can be prepared in good yields by three-component reactions from activated formic acid, sulfur dioxide, and polarized vinyl compounds.     

Synthesis of a novel 18β-glycyrrhetinic acid derivative

A novel compound, biotinylated 18β-glycyrrhetinic acid (BGA), was synthesized. It is a compound of 18β-glycyrrhetinic acid linked with biotin. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 266–267, May–June, 2006. An erratum to this article is available at .     

Unusual ion pairs and their relationship to acid ionization

Osmotic and activity coefficients, determined from isopiestic measurements, are presented for aqueous solutions of eight tetramethylguanidinium salts. It is proposed that both hydronium and tetramethylguanidinium ions are capable of forming stable ion pairs with many anions by means of bridged hydrogens forming six-membered rings and that these ion pairs are stable in rather dilute aqueous solutions.     

无保护流体室温燐光法测定吲哚-3-丁酸的研究

在仅以碘化钾为重原子微扰剂、亚硫酸钠为除氧剂及无任何保护性介质存在的水溶液中 ,吲哚_3_丁酸 (IBA)能发射很强的室温光 (RTP) ;详细研究了分析测定条件及有机溶剂对RTP的影响 ;在最大光波长λex/λem =281/447nm处 ,光强度与IBA浓度在2.0×10 -7～1.0×10 -5mol/L范围内呈良好的线性关系 ,检出限4.3×10-8 mol/L ;方法直接用于强化水样和土壤中IBA的测定 ,回收率96 %～104 % ,相对标准偏差2.37 %～3.97 %。