查询词典 cyclic group

In the presence of catalytic rhodium acetate, ethyl 2-diazo-3-oxo-per fluoroalkanoates, reacted readily with nitriles to give a series of 5-fluoroalkyl substituted 1, 3oxazoles with high regio-selectivity through a metal carbenoid intermediate. The reactions of carbenoids with noncyclic vinyl ethers or cyclic vinyl ethers afforded dihydrofuroates in good to excellent yields. Interestingly, only vinyl C-H insertion compound was obtained concerning of the reaction of carbenoids with 2, 5dimethylfuran due to the steric hindrance of methyl group

醋酸铑分解2-重氮-3-氧代-全氟羧酸乙酯形成的金属卡宾作为1，3-偶极体，可以与一系列芳基或烷基取代的腈反应，高度区域选择性地生成一系列4-乙氧羰基-5-氟烷基取代的噁唑化合物；也可以与富电子的链状和环状的烯基醚反应，以优良的产率得到一系列氟烷基取代的二氢呋喃类化合物；而与2，5-二甲基呋喃的反应，由于甲基的位阻作用，只得到金属卡宾对呋喃3-位烯基碳氢键插入产物。

Hemes are cyclic tetrapyrroles that contain iron and commonly found as the prosthetic group of hemoglobin , myoglobin and the cytochromes .

血红素是含铁的环状四吡咯，它作为辅基，普遍存在于血红蛋白肌红蛋白和细胞色素中。

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。