查询词典 reaction ring

The optimum reaction conditions are obtained by orthogonal exptl. design; ring-opening reaction:n:n = 1:1.3, Hexamethylenetetramine catalyst 0.7%,reaction temp. is 80℃, reaction time is 7 h, and concentration of inhibitor is 0.3%. ring-closing reaction : n:n=1:0.9, reaction temp. is 40℃, reaction time is 5 h.

通过正交设计确定了最佳工艺条件为：开环反应：六次甲基四胺用量0.7%(占反应物总量的质量百分比)，阻聚剂用量0.3%(占反应物总量的质量百分比)，ECH：MAA的摩尔比为1.3：1，温度80℃，反应时间7h ；闭环反应：氯醇酯： NaOH的摩尔比为1：0.9，反应温度40℃，反应时间5h。

The pigment in colored cotton fibers was extracted by methanol at room temperature. The results of color reactions HCl-Mg reaction, NaBH4 reaction, NaOH reaction, FeCl3 reaction and Pb(Ac2 reaction of the pigment extractive showed that the pigment extracted by methanol was flavone or flavonol with two adjacent hydroxide groups (Table 2, Fig. 1). The results of UV spectral analysis further proved that the pigment extracted by methanol from brown fiber belonged to flavone with two adjacent hydroxide groups in B ring, and that from the green fiber contained not only flavone but also flavonols with two adjacent hydroxide groups both in A ring and B ring and indican replaced a hydroxide group at 3-site of A ring Fig.

通过盐酸－镁粉反应、四氢硼钠还原反应、碱反应、醋酸铅反应、氯化铁反应和紫外光谱吸收的分析表明，甲醇室温提取的棕色棉纤维色素可能是黄酮类化合物，B环上带有邻二酚羟基；甲醇室温提取的绿色棉纤维色素除黄酮类化合物外，还含有3-位羟基被糖甙化的黄酮醇类化合物，A、B环上都带有邻二酚羟基。

Since aromatic ring is a very stable compound, it would needs very high activation energy to begin the ring opening reaction. It is therefore interesting to investigate how the micro-organism can catalyze this reaction in room temperature at natural buffer condition.

由於芳香环是一种非常稳定的化学结构，如果想要进行开环反应必要要经过极大的活化能，而了解生物体中是如何在常温的环境下进行这样的反应将会是非常有趣的题材。

Can induce the reaction of cleavage H atom from methyl on the ring of deactivated toluenes,such as nitrotoluene. The carbanions caused by base are the very important reaction intermediums, which determined the reaction rate and reaction effect.

该反应体系中，NaOH的加入对此催化反应起着相当关键的作用，研究表明强碱也能像温度一样促进苯环卜甲基的摘氢速度，使底物形成相应的硝基苯甲基阴离子，稳定的硝基苯甲基阴离子是氧化反应进行的重要中间体。

Results indicated that introducing some ring-structure into UF molecule during the synthesis could efficiently improve the water resistance of UF resin. The Uron ring would form if reaction temperature was more than 75 degrees C, and the higher Uron content was obtained at pH 8 and 85 degrees C in the absence of catalyst when the reaction time was long enough.

结果表明：通过在脲醛树脂合成中引入Uron环等环状结构物质能够有效提高脲醛树脂胶黏剂的耐水性；当反应温度高于75℃时，反应产物都生成了一定量的Uron环物质；在pH值为8左右、温度控制在85℃、不使用催化剂、尽可能延长反应时间的条件下，尿素与甲醛成环化反应生成的Uron相对值最多。

At Pt electrode, DHA undergoes hydration reaction to form bicyclic product, and then further transform into 2, 3-diketogulonic acid and its enol form via the opening of lactone ring. At CuCoHCF/Pt electrode, DHA undergoes ring-opening reaction followed by degradation reactions.

但后行反应不同：在裸Pt电极上，DHA进行水化反应生成了双环结构产物，而后开环形成羧酸或烯醇结构；在CuCoHCF/Pt电极上，DHA水化反应生成开环产物，进一步又发生降解反应。

In chapter 3, general reaction of a-hydroxy epoxides were introduced. We have developed a newly gold-catalyzed ring opening reaction ofα-hydroxy epoxides containing carbon cycle. We have disclosed the rule of ring opening reaction. And the plausible mechanism was proposed.

第三章：首先介绍了α-羟基环氧化合物的反应，其次介绍了一个新的金催化的含碳环骨架的α-羟基环氧化合物开环反应，总结了反应规律，提出了可能的反应机理。

From the potential energy profile, it can be predicted that, the dominant channel of this reaction consists of three steps: the two reactants first form a three-membered ring intermediate (INT1) through a barrier-free exothermic reaction of 19.2 kJ/mol; three-membered ring intermediate (INT1) isomerizes to a four-membered ring silylene(P2) via the transition state (TS2) with an energy barrier of 22.8 kJ/mol; four-membered ring silylene(P2) further reacts with ethene(R2) to form a silicic bis-heterocyclic compound (P3), which is also a barrier-free exothermic reaction of 132.2 kJ/mol.

用CCSD//MP2/6-31G*方法研究了单重态二甲基亚烷基硅烯与乙烯生成硅杂双环化合物环加成反应的机理，根据该反应的势能面可以预言，该反应的主反应通道有三步组成：第一步是两反应物（R1， R2）首先生成了一三元环中间体（INT1），它是一无势垒的放热反应，放出的能量为19.2 kJ/mol；第二步是三元环中间体(INT1)经过渡态TS2异构化为了四元环硅烯（P2），其势垒为22.8 kJ/mol；第三步是四元环硅烯（P2）进一步与乙烯(R2)反应生成了硅杂双环化合物（P3），该反应也是一无势垒的放热反应，放出的能量为132.2 kJ/mol。

The result shows that the elimination reaction and ring closing reaction are synergistic, and the hydrogen in the elimination reaction derives from hydroxyl. In addition, the activation energy of the reaction is 139.2kJ/mol.

计算结果表明，该反应中的消除反应和成环反应是协同进行的，溴化氢消除反应中的氢来自与O(22)相连的羟基氢，反应的活化势垒为139.2kJ/mol，反应放热25.1kJ/mol。

Based on the-references on the thermal imidization of polyand the polymer composition analysis,the thermal imidization mechanism of SMA with aniline was demonstrated to be a two-stage consecutive reaction,in which a second-order reversible ring-opening reaction of SMA to produce poly(styrene-co-N-phenyl-maleamic acid)and a first-order irreversible intrachain ring-closing reaction to form SNPMI were involved.

论文首先参考聚酰胺酸热环化反应，并通过SMA酰亚胺化产物的组成分析，确定了SMA与苯胺的热酰亚胺化反应机理为一个包含由SMA生成苯乙烯—N-苯基马来酰胺酸共聚物的二级可逆开环反应以及由SNPMA生成苯乙烯—N-苯基马来酰亚胺共聚物的一级不可逆分子内闭环反应在内的串联反应过程，其中第二步SNPMA闭环反应为控制步骤。

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。