异构体

In contrast, the conformer with trans-trans arrangement is unstable and the energy is higher.

反之，完全采用trans-trans排列的旋转异构体构象能量较高，不稳定。

Synthesis and Structure of 1-(m-Methoxyphenyl)-2- cyclohexanol

对反应的立体化学进行了分析，并用13CNMR谱确定了顺反异构体的构型。

The results of density functional calculations indicate that the enol form E1 is the most stable tautomer at the ground state.

研究结果表明，醇式异构体E1为2-(2-巯苯基)苯并噁唑的优势构型；在E1向K转变过程中，存在一个较小的能垒；当考虑零点振动能后，逆向能垒消失。

Meanwhile, the isomer with a larger change of dipole moment has larger value of the first hyperpolarizability during the charge-transfer process.

5， 6， 7顶点双取代碳硼烷桥连分子受推拉电子基的影响，5， 6， 7顶点碳硼烷的构型发生一定变化，碳硼烷中两个C原子间的距离变长；同时碳硼烷中两个C原子取代位置的不同，影响了分子的稳定性和极化率，取代基团与碳硼烷中成键数较低的C原子相连的异构体，稳定性较好且具有大的极化率； 5，6，7顶点双取代碳硼烷桥连分子形成一维结构有利于分子内电荷转移，在电荷转移过程中偶极矩变化较大的体系，其二阶NLO系数也较大。

On the other hand, 3(2)-fluoro-4-methoxyl methyl benzyl alcohol and 3(2)-fluoro-4-methyl benzyl alcohol are mixture and components of pyrethrum esters. Both of them have "mixture fluorine effect " and higher activity, lower drug resistance. As we know, the mixture benzyl alcohol containing fluorine is more easy to be synthesized than the single, so the cost of preparation is lower. We hope to apply it to molecule design of the new agriculture chemical. On the base of molecule design and structure-activity relationship research of pyrethric acid II and mixture of alcohol containing fluorine, we intend to get new pyrethrum ester that have higher activity and lower resistance.

另一方面，混合含氟对甲氧甲基苄醇和混合含氟对甲苄醇都是具有"混合氟效应"的高活性、低抗性的拟除虫菊酯醇组分，由于混合含氟醇的合成要比单一异构体的合成容易，成本较低，本文希望将其应用到新农药的分子设计中，用第二菊酸和一些含氟醇进行分子设计及进一步的构效关系的研究，筛选出一些高活性低抗性的拟除虫菊酯换代新品种。

Molecular structures of fourteen 6-thioxanthine tautomers were calculated by the B3LYP/6-311G** method, both in gas and aqueous phases, with full geometry optimization. The Onsager solvate theory model was employed for aqueous solution calculations.

在密度泛函B3LYP/6-311G**水平下，对14种气相和水相中可能存在的6-硫代黄嘌呤异构体进行了几何构型的全自由度优化，并计算出它们的总能量、焓、熵、吉布斯自由能。

In stereoisomerism, substances with the same atoms are bonded in the same ways but differ in their three-dimensional configurations.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

In stereoisomerism, substances with the same atoms are bonded in the same ways but differ in their three-dimensional configuration s.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

In stereoisomerism, substances with the same atom s are bonded in the same ways but differ in their three-dimensional configurations.

第二种类型是立体同分异构体，具有相同原子的物质以相同的键合方式结合，但它们的三维构型不同。

Based on the fact that the stable tautomer of NTBC by calculation is different from that from X-ray experiment, the quantitative structure-activity relationship (Comparative Molecular Field Analysis, CoMFA and Comparative Molecular Similarity Index, CoMSIA) were studied on the five possible active tautomers in order to conjecture the structure of NTBC binding with HPPD.

基于理论计算得到的NTBC的稳定异构体结构与实验观测结构不一致的事实，利用比较分子力场和比较分子相似性指数的分析方法对NTBC可能存在的五种活性结构分别进行了三维构效分析，最终由CoMFA分析得到的最佳模型所对应的NTBC的活性结构与动力学实验推测的结合模式相吻合。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。