选择性

Hydroxynitrilelyase, a vital tool in the bio-synthesis of optically active cyanohydrin, which can catalyze carbonyls and HCN selective forming optically active cyanohydrin.

醇腈酶(α-hydroxynitrilelyase， HNL)是手性醇腈化合物生物合成十分有用的工具，能够催化羰基化合物和HCN立体选择性的加工形成手性醇腈化合物。

Under the optimized conditions, in-situ-generated N,N -dioxide from the corresponding amide (10 mol%) and m-CPBA (20 mol%) retained the same asymmetric catalytic activity and enantioselectivity, and most of the aromatic,α,β-unsaturated, heterocyclic, aliphatic and steric hindrance ketones could be converted into the corresponding cyanohydrin trimethylsilyl ethers in up to 99% yield and 93% ee.

底物扩展证明，该有机小分子催化体系对芳香酮、杂芳香酮、脂肪酮、位阻酮以及α，β-不饱和酮都具有优良的手性诱导能力，收率高达99％，对映选择性达93％ee。

We speculate that the reaction takes place through a Pictet-Spengler cyclization mechanism.

反应对芳香醛和脂肪醛都具有较高的收率，较高的区域选择性。

In this regard, this dissertation focuses on the regioselectivity of radical chemistry and conducts theoretical studies on product-oriented radical cyclization reactions.

本论文从自由基反应的区域选择性着手，对导向有机合成的自由基环合反应进行理论研究。

The influences of solvent, reaction temperature, and time on the conversion of cyclohexane were examined.

以环己烷氧化为探针反应，考察了上述负载催化材料的催化性能并分析了不同金属离子或取代基对催化剂活性及选择性的影响。

In the condition of 1 MPa O_2 and 413 K for 4 h, the conversion of cyclohexane is 16.9%, and the total selectivity of cyclohexanol and cyclohexanone is 93%.

在该反应条件下，环己烷的转化率为16.9％，环己酮和环己醇的总选择性为93％。

It is of great academic and practical importance to study and develop highly efficient and environmentally friendly catalytic cyclohexane oxidation processes.

本文尝试采用普通氧化物负载的纳米金催化剂用于以氧气为氧化剂的环己烷选择性氧化反应。

The characteristics of cyclohexane oxygen-enriched oxidation were studied.

研究了环己烷富氧氧化的特征，考察了进气氧浓度的提高对反应速度、选择性、安全性和经济性的影响。

The results indicated that higher phenol conversion and cyclohexanol selectivity could be obtained under the condition of higher temperature and pressure, and lower space velocity and methanol content, while phenol concentration had almost no effect on the reaction performance.

结果表明，较高的反应温度和压力以及较低的液体空速和甲醇含量有利于提高苯酚的转化率和环己醇的选择性，但是苯酚的浓度对反应性能的影响不大。

Under the suitable conditions of reaction temperature 170℃, 1.5 MPa air and reaction time 6 h, the conversion of cyclohexane and the total selectivity of cyclohexanone and cyclohexanol were 5.39% and 88.7% respectively.

在反应温度170℃，空气压力1.5 MPa，反应时间6 h的优化条件下，环己烷转化率与酮醇总选择性分别为5.39%和88.7%。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷