STUDIES ON SELF-VULCANIZING FLUOROELASTOMER/PHENOL HYDROXY SILICONE RUBBER BLENDS

Self-vulcanizing blends of phenol hydroxy silicone rubber(PHSR)and fluoroelastomer(FPM)were prepared. Vulcanized rubbers with lower glass transition temperature(T_g)were successfully obtained.The results of dynamic mechanical analysis(DMA)show that the vulcanized FPM/PHSR(10 phr)blend has only one T_g temperature,demonstrating the well compatibility between FPM and PHSR.The thermogravimetric analysis(TGA)demonstrates that the PHSR do little damage to the thermal stability of FPM.The vulcanization charact...     

Three New Alkaloids from the Leaves of Uncaria rhynchophylla

Three new alkaloids, 2′‐O‐β‐D ‐glucopyranosyl‐11‐hydroxyvincoside lactam ( 1 ), 22‐O‐demethyl‐22‐O‐β‐D ‐glucopyranosylisocorynoxeine ( 2 ), and (4S)‐corynoxeine N‐oxide ( 3 ) were isolated from the leaves of Uncaria rhynchophylla, together with four known tetracyclic oxindole or indole alkaloids, isocorynoxeine N‐oxide ( 4 ), rhynchophylline N‐oxide ( 5 ), isorhynchophylline N‐oxide ( 6 ), and dihydrocorynantheine ( 7 ), and an indole alkaloid glycoside, strictosidine ( 8 ). The structures of 1 – 3 were elucidated by spectroscopic methods including UV, IR, ESI‐TOF‐MS, 1D‐ and 2D‐NMR, as well as CD experiments. The activity assay showed that 8 (IC₅₀=8.3 μM ) exhibited potent inhibitory activity on lipopolysaccharide(LPS)‐induced nitrogen monoxide (NO) release in N9 microglia cells. However, only weak inhibitory activities were observed for 1 – 7 (IC₅₀>100 μM for 1 – 6 or >30 μM for 7 ).     

Monoclinic iron hydroxy sulphate: A new route to electrode materials

The monoclinic form of FeOHSO₄ was prepared by dehydration of FeSO₄·7H₂O. We show that reversible insertion of up to 1Li/f.u. is possible in this compound at an average voltage of 3.2 V. The insertion/deinsertion is a biphasic process. The high voltage plateau, a reversible capacity of 110 mAh/g after 20 cycles and good cycling behavior make this compound an attractive positive electrode material for rechargeable Li-ion batteries, suggesting also that transition metal sulphates need to be explored.     

Me‐BIPAM for the Synthesis of Optically Active 3‐Aryl‐3‐hydroxy‐2‐oxindoles by Ruthenium‐catalyzed Addition of Arylboronic Acids to Isatins

A chiral O‐linked C₂‐symmetric bidentate phosphoramidite (Me‐BIPAM) was found to be efficient for the ruthenium‐catalyzed addition of arylboronic acids to isatins. Asymmetric synthesis of 3‐aryl‐3‐hydroxy‐2‐oxindoles by 1,2‐addition of arylboronic acids to isatins was carried out in the presence of [RuCl₂(PPh₃)₃]/(R,R)‐Me‐BIPAM and KF, resulting in an enantioselectivity as high as 90 % ee. It was found that the reaction with N‐protected isatins proceeds with high yields and good enantioselectivities. The best protective groups on the nitrogen atom were different depending on the substituents on the aromatic ring. The use of a N‐benzyl group resulted in excellent enantioselectivities in many substrates compared with other groups.     

Metal‐Free Oxidation of α‐Hydroxy Ketones to 1,2‐Diketones Catalyzed by Mesoporous Carbon Nitride with Visible Light

As a photocatalyst, mesoporous carbon nitride (mpg‐C₃N₄) shows higher photocatalytic activities in organic synthesis. Herein we report an mpg‐C₃N₄‐catalyzed oxidation of α‐hydroxy ketones to synthesize 1,2‐diketones using visible light. This transformation represents a green and highly efficient synthetic route to synthesize 1,2‐diketones for which catalytic approaches are scarce.     

Enantioselective Synthesis of Tertiary α-Hydroxy Phosphonates Catalyzed by Carbohydrate/Cinchona Alkaloid Thiourea Organocatalysts

A pinch of sugar: The new bifunctional carbohydrate/cinchonine-based thiourea 1 has been designed for the asymmetric addition reaction of α-ketophosphonates and trimethylsilyl cyanide, the product of which can be hydrolyzed to afford tertiary α-hydroxy phosphonates with excellent enantioselectivities.     

Hydroxy Naphthol Blue as a Spectrophotometric and Fluorometric Reagent for the Uranyl Ion

Abstract

The utility of hydroxy naphthol blue (HNB) as a spectrophotometric and fluorometric reagent for the uranyl ion has been investigated. In phthalate buffer (at a pH of 4.0), UO₂ ²⁺ forms a brown complex of low absorptivity with the red form of HNB. By following the decrease in HNB absorbance at 530 nm (which has ε = 4.1 × 10³) uranyl ion can be determined to levels as low as 1.1 × 10^?6 M (0.30 μg/ml). HNB also emits at 460 nm when excited at 365 nm at these pH values, while the UO₂ ²⁺ complex exhibits greatly reduced emission. Examination of the quenching of HNB emission by UO₂ ²⁺ allows the determination of uranyl ion to levels as low as 3.2 × 10^?6 M (0.86 μg/ml). A 1:1 type complex was formed between UO₂ ²⁺ and HNB, and a formation constant of 9.77 × 10³ (log K₁ = 3.99) was measured for the complex.     

新型共轭高分子聚[吡咯2,5-二(3-甲氧基-4-羟基苯甲烯)]的合成与表征

本文采用两步法合成了一种新型共轭高分子聚 [吡咯 2 ,5 二 (3 甲氧基 4 羟基苯甲烯 ) ],其前聚物聚 [吡咯 2 ,5 二 (3 甲氧基 4 羟基苯甲烷 ) ]可溶于一般的极性有机溶剂 .通过红外、核磁、紫外光谱分析鉴定了产物及其前聚物的结构 .利用DSC与TGA测试分析了所合成聚合物的热学性质 .紫外光谱表明在聚合物链中引入醌式吡咯环结构有利于降低产物的能隙 ,其能隙为 1 14eV ,属窄能隙类共轭聚合物 .经碘掺杂后产物的电导率在半导体的范围内     

2-羟基-1O,11-二氢-5H-二苯并[a,d]环庚烯-5-酮的合成

以2－羟基苯甲醛和3－甲氧基苯乙酸为原料,经3步反应合成2－羟基－10,11－二氢－5H－二苯并[a,d]环庚烯－5－酮。     

Estimation of oxyhydroxide specific surface area using the amounts of OH groups adsorbed

A procedure for pH-metric determination of the limiting adsorption of OH groups (A _OH) by Fe^III, Zr^IV, Cr^III, and In^III oxyhydroxide hydrogels from 0.1 and 1.0 M solutions of NaCl is described. Data on the molecular area occupied by a single OH group on the hydrogel surface (S _OH) and the S _spec values, which were calculated from A _OH and S _OH, are presented. The S _spec value does not depend on the pH of hydrogel precipitation; the true S _spec value can be determined only from sorption of the OH groups at the actual point of zero charge of the hydrogel. The A _OH values for hydrogels were found to change only slightly during aging of hydrogels in electrolyte solutions.