查询词典 steric

It is researched that the global structure of modified lignosulphonate is dispersive and less cluster structure to benefit the adsorption efficiency, the adsorption capacity and to improve the lyophobic surface of coal;. the film thickness is double by the comparison of lignosulphonate and modified lignosulphonate in the respect of the space steric hindrance.

研究表明：改性木钠球形结构更加分散，簇状结构明显减少，对提高吸附效率，增加吸附量，极大程度地改善煤表面的疏水性极为有利；改性木钠的空间位阻作用与未改性木钠相比较，其表面吸附膜厚度增加1倍左右。

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。

Our calculations suggest that this class of non-classical transplatin analogues with one nonplanar heterocyclic amine decreases the equatorial steric effect and the hydrolysis reaction barriers.

计算表明，这些含有非平面杂环胺反铂的配合物减小了赤道面上的立体效应和水解势垒。

Nevertheless, the yield of pinacol was also strongly affected by the steric environment surrounding the carbonyl group. The pinacol coupling of aromatic aldehydes has been achieved with high yields under such a condition. However, the diastereose-lectivities of pinacols were not satisfying. Unfortunately, the ketones and most aliphatic aldehydes appeared inert under the same reaction conditions.

然而， 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大，在此条件下，锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应，得到的呐醇产率高，但非对映异构体选择性差，而脂肪族醛类化合物得到的呐醇产率较低，在同样的条件下，酮类化合物不能顺利进行呐偶合反应。

Mechanism of high despersity and dispersion stability of polycarboxylic superplastizers can be explained well with steric effect.

究其原因，与传统的超塑化剂萘磺酸和磺化三聚氰胺缩合物相比，他们能在低掺量下赋予混凝土高分散性及高分散体系稳定性防止塌落度

Mechanism of high despersity and dispersion stability of polycarboxylic superplastizers can be explained well with steric effect.

用空间位阻效应可较好解释该类超塑化剂对水泥分散及分散稳定性作用机理。

The reactions of benzaldehydes bearing an ortho substituent group on the phenyl ring with propargyl bromide may yield a mixture of regioisomers (homopropargyl and homoallenyl alcohols) or a single homoallenic alcohol due to the steric effect.

邻位上的取代基由于位阻原因往往使反应得到含有高丙二烯醇和高炔丙醇的混合物或者单一的高丙二烯醇。

However, three isomers are obtained when [3(5)-〓-5(3)-MeS]pyrazole or[3(5)--5(3)-MeS]pyrazole reacts with 〓 in the same conditionpossibly owing to the influence of both the steric and electronic factors.

通过配体与〓的光化学反应，首次分离得到了不对称取代的双吡唑烷VIB金属配合物，但3位取代基的立体位阻减弱了双吡唑烷与〓的反应。

The results show thatthe substitutions containing sulfur atom in the pyrazole ring remarkably affectthe steric and electronic properties of the pyrazole ligands.

因此，我们研究了吡唑环上带上S原子取代基对形成双吡唑烷配体及其与VIB金属羰基配合物的光化学反应的影响。

With NMR and DFT methods, the Michael additions of alkynyl Fischer carbene complex with a series of substituted pyrazoles as nucleophiles were also studied. All reactions follow the same three-step pathway mechanism described above. Substituents on 3-, 4- and 5- positions of the pyrazolyl ring affect the reaction in the steric and electronic manners, even to change the rate-determining step.

一系列取代吡唑与1-炔基Fischer卡宾化合物的Michael加成反应都遵循前面提出的三步机理，其中吡唑的3-， 4-， 5-位分别从电子效应和立体效应方面不同程度地影响着反应的进行，甚至改变反应的决速步骤。

But we don't care about Battlegrounds.

但我们并不在乎沙场中的显露。

Ah! don't mention it, the butcher's shop is a horror.

啊！不用提了。提到肉，真是糟透了。