查询词典 reaction ring

The conversion of the cyclobutanes to the corresponding annulation products was achieved by a reaction sequence of [elimination of HCl in the cyclobutanes-4 electron electrocyclic ring opening-6 electron electrocyclic ring closure-elimination of another HCl molecule] .

这些环丁烷产物向增环产物的转化是经一个[脱除－分子HCl得环丁烯－环丁烯电环开环为丁二烯－6电子电环闭环－脱除另一分子HCl]这一连续反应进行的。

1H NMR spectroscopic analysis of aromatic protons combined with theoretical analysis of molecular structures proved the existence of two rotational isomers at 300 K, as well as a rapid interconversion equilibrium at 330 K for both compounds Ⅰ and Ⅱ. However, only one conformer exists for compound Ⅲ and puerarin containing 7-phenolic hydroxyl instead of propyl in A-ring as the case of compounds Ⅰ and Ⅱ. Based on UV-Visible absorption data of neutral and basic solutions, and on the density function calculations, the 7-phenolic hydroxyl group in A-ring was found to be more acidic than the 4'-phenolic hydroxyl group in B-ring. The mechanism of derivation reaction and the structure-reactivity relationship of puerarin as an antioxidant were further discussed.

其中7-丙基葛根素Ⅱ属于新型取代衍生物；变温1H NMR和理论计算结果表明，在300 K时，葛根素和4'-丙基葛根素以单一构型存在；而7，4'-二丙基葛根素和7-丙基葛根素则存在两种核磁可分辨的旋转异构体，当温度升至330 K时，两种异构体可以相互转化；通过对比分析葛根素及其衍生物脱质子产物的紫外可见吸收光谱并结合理论计算，确定了A环上7位酚羟基比B环上4'位酚羟基先脱去质子，并由此进一步阐明了葛根素衍生化反应机理以及在抗氧化作用中可能的活性位点和结构活性关系。

In our research on study chemical reaction of active methylene compounds and brom-acetophenone. Because of brom-acetophenone is compound that contain carbonyl and halogen ,which will take place electrophilic substitution and nucleophilic addition. When active methylene compounds are ethyl acetoacetate and β-diketone, controlling reaction condition, we have found that mono-substitution's production and di-substitution's. production is isolated; active methylene compounds are acetoacetanilide and acetoacetanilide derivate, pyrrolidin-2-one derivants were obtained by substitution and close-ring reaction .but there is no report about it.

本文是让活泼亚甲基类化合物与溴代苯乙酮发生化学反应，由于溴代苯乙酮是含有羰基的卤代烃结构，它可以发生亲电取代和亲核加成反应，当活泼亚甲基类化合物为乙酰乙酸乙酯和β-二酮时，控制反应条件可以发生单取代和双取代两种产物；当活泼亚甲基类化合物为乙酰乙酰芳胺类化合物来反应时，溴代苯乙酮中的羰基与氨基会发生分子内的关环反应生成吡咯烷-2-酮衍生物，这在以前的研究中是没有发现的。

The author found that the chromone ring could be cleaved at high temperature in PPA, and the change of the ratio of ring-opened product versus the target one with the change of reaction time and temperature was investigated in details.

我们采用了两条不同的合成路线合成了第Ⅳ类化合物，对部分反应条件进行了优化，在研究过程中发现了色酮化合物在高温下的开环反应及多聚磷酸的水解作用，并对前者进行了详细研究了，获得了不同反应温度和时间下未开环产物和开环产物的比例，得到了制备相应的未开环产物和开环产物的最佳反应条件。

The double bond in norbornene ring of TCPD was easily saturated at a low temperature, and an intermediate 12,13-dihydrotricyclopentadiene (12,13-DHTCPD) was formed. Higher temperature and hydrogen pressure were required for the saturation of remaining double bond in cyclopentene ring to generate a completely hydrogenated compound tetrahydrotricyclopentadiene.That is to say, the reaction occurred via the TCPD→12,13-DHTCPD→THTCPD route.

采用气质联用、红外光谱和核磁共振对加氢产物进行表征，发现在加氢反应中TCPD的降冰片烯双键首先被饱和，生成中间产物12，13-二氢三环戊二烯(12，13-DHTCPD)，残留的环戊烯双键需要在更高的温度和氢压下反应生成四氢三环戊二烯，即反应按照TCPD→12，13-DHTCPD→THTCPD的途径进行。

First, the preparation of the aminom ethylation of tannin using its electrophilic reaction activity of C-6, C-8 in ring-A; then process the quaternization base on the aminom ethylation; last, progress the sulfonation by use of the activity of phenolic hydroxyl hi ring-B.

首先利用单宁A环的C—6、C—8的亲电反应活性制备单宁胺甲基化产物；然后在胺甲基化的基础上进行季胺盐化；最后利用单宁B环的酚羟基的活性进行磺化。

This result again showed that in the process of the reaction of flavonoidswith α-hydroxy ethyl peroxyl radicals, 2,3-double bond in the C ring of flavonoidsplays a more important role than o-dihydroxy in the B ring.

这进一步说明了黄酮类化合物与有机过氧自由基反应的过程中C环2，3双键比B环邻二羟基起着更重要的作用。

In order to identify the ring-opening reaction between hydroxyl group and epoxide group, an analogous reaction was performed and the effect of reaction environment on conversion ratio was discussed in detail.

文中对羟侧基和环氧基的开环反应进行了模拟，并对大分子的反应程度及其影响因素进行了较详细的研究。

Research on thermodynamics and kinetics of pyrolysis reaction mechanism Kinetic and thermodynaimic research of the pyrolysis reaction mechanism of toluene was conducted at different temperature range 298-1223K. The result shows that the pyrolysis reaction firstly occurs at the methyl on the benzene ring, and produces benzyl.

裂解机理的热力学与动力学研究在298K-1223K的温度范围内对甲苯热解机理的热力学和动力学研究结果表明，热解首先发生在苯环甲基C-H键上并生成卞基自由基，主要产物为联二甲苯，反应的活化能ΔE〓=402.27kJ/mol。

It can be proposed that the TS-1/H〓O〓 catalyzed opening ring reaction of propylene oxide was an heterogeneous catalytic reaction occurred on the active sites on the surface of the catalyst, not an homogeneous reaction catalyzed by H〓.

根据已知的实验结果可以推断，TS-1/H〓O〓催化的PO的开环反应是发生在催化剂表面活性位上的非均相催化反应过程，与H〓催化的均相反应不同。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。