Rotational Phenomena on Substituent Phenyl Rings of (η5-Cyclopentadienyl)(η4-Tetraphenylcyclobutadiene)Cobalt

We used extended Hückel calculations, variable-temperature, homonuclear long-range shift-correlated 2-D ¹H NMR and dynamic NOE measurements to investigate rotational phenomena of substituent phenyl rings on (η⁵-cyclopentadienyl)(η⁴tetraphenylcyclobutadiene)cobalt (1). Two closely related compounds, (η⁵-cyclopentadienyl)(η⁴-1,3-diphenylcyclobutadiene)cobalt (A) and (η⁵-cyclopentadienyl)(η⁴-1,2-diphenylcyclobutadiene)cobalt (A′), were prepared. Energy minima appeared at conformations of which the dihedral angles between phenyl and cyclobutadiene rings are about 30° for I and 0° for A according to extended Hückel calculations. In 1, ortho protons of phenyl rings belong to one set of multiplet in ¹H NMR; meta and para protons belong to the other. It was supported by a long-range coupling 2-D ¹H NMR and NOE experiments. A sharp line due to phenyl rings was observed in the low-temperature ¹H NMR spectrum of A, which indicates that the five protons are magnetically equivalent at that temperature.     

Liquid Chromatography of Adenine,Caffeine, Theobromine,Theophylline, Tannic Acid,Xanthine and its Application to Tea Analysis

A polystyrenesulfonic acid resin in the hydrogen form is a useful stationary phase for chromatographic separation of adenine, caffeine, theobromine, theophylline, tannic acid, xanthine and tea components with aqueous ethanol as eluent. The results indicated that caffeine, theophylline, theobromine, adenine, xanthine and tannic acid could be separated on a column of Dowex-50W-X8(H)⁺ by elution with 25% ethanol as eluent.     

湿法消解-ICP-AES测定核桃仁中的无机元素

用HNO3做消解剂湿法消解,电感耦合等离子体-原子发射光谱法(ICP-AES)测定了核桃仁中的无机元素.通过加标回收率实验,说明了此方法的可靠性和准确度,表明只用硝酸消解核桃样品方法可靠、安全,为测定核桃仁的营养成分供了理论依据.     

离子液体/水混合溶剂促进芳醛与罗丹宁的缩合反应

在室温条件下, 离子液体1-正丁基-3-甲基咪唑四氟硼酸盐([bmim]BF₄)与水组成的混合溶剂能有效催化一系列芳醛与罗丹宁反应, 以80%～93%的产率生成相应的5-芳亚甲基-2,4-噻唑二酮. 离子液体[bmim]BF₄催化活性高, 反应在10～120 min内完成. 实验结果表明该法反应条件温和、产率高、反应时间短、后处理简单、离子液体可重复使用.     

Liquid Chromatography of Benzoic Acid and Phthalic Acid on Ion-Exchange Resin

This is to report a study in which cation ion-exchange resin serves as the stationary phase for liquid chromatography of benzoic acid and phthalic acid and aqueous ethanol acts as the mobile phase. No ion. exchange phenomenon is involved. It is rather a solvent action on the polymer matrix for the organic solutes. It was found that the elution volumes depend on the pKa values of the acids; the higher the pKa value the more the retention volume.     

The Synthesis and Chemistry of 8-Substituted Bicyclo[5.1.0]oct-1(8)-ene

8-Bromobicyclo[5.1.0]oct-1(8)-cne (7), an intermediate for the preparation of 8-substituted bicyclo[5.1.0]oct-1(8)-enes, was synthesized by denomination of 1,8,8-tribromobicyclo[5.1.0]octane (6). Compound 7 underwent bromo-lithium exchange followed by nucleophilic substitution reactions to generate bicyclo[5.1.0]oct-1(8)-ene (5), 8-methylbicyclo[5.1.0]oct-1(8)-ene (10), and 8-trimethylsilylbicyclo[5.1.0]oct-1(8)-ene (11). The bicyclic cyclopropenes 7, 5, 10, and 11 reacted with cyclopentadiene to form adducts 12, 13, 14, and 15, respectively. All of these Diels-Alder adducts are endo-exo isomers (endo-addition from the view of the cyclopropene and exo-addition from the view of the cyclooctene).     

Rapid Synthesis of 1,2,3,4-Tetrahydropyrimidin-2-ones Using Zn（NH2SO3）2 as a Catalyst under Microwave Irradiation

Rapid synthesis of 1,2,3,4-tetrahydropyrimidin-2-ones （THPO） from aromatic aldehydes, β-ketoester and urea （or thiourea） using zinc sulfamate as the catalyst under microwave irradiation was described here. Compared with the classical Biginelli reaction, this new method consistently has the advantages of good yields （76%-96%）, short reaction time （3-15 min）, no corrosion to equipments, ease of manipulation, and low cost catalyst.     

荧光猝灭法测定饮料中的维生素C

在pH10.7的NH3-NH4Cl缓冲溶液中,维生素C在一定浓度范围内能活化氯化血红素酶催化H2O3氧化L-酪氨酸的反应,荧光猝灭程度与维生素C的浓度具有一定线性关系.在最佳实验条件下,方法的线性范围为0.8-25.6μg/mL,相对标准偏差4.25%,检出限为0.0112μg/mL,并考察了介质和常见物质的干扰情况.方法用于实际样品的测定,结果满意.