异构体

Write the structural formula for an alkyne hydrocarbon having the fewest number of C's, which has geometric isomers, and give the IUPAC name for both geometric isomers.

答：写出有几何异构体的，含碳原子数最少的炔烃的结构式，并对所有的异构体用IUPAC命名法命名

Configurational isomerism is then due to the presence in the molecule of one or more dissymmetric centres ,in the simplest case asymmetric carbon atoms ,each of which can have and absolute configuration; and ,or ,to the presence of double blonds which can give cis- and trans-geometrical isomers .

构型异构是由于分子中存在一个或一个以上的不对称中心，在最简单的情况下是不对称碳原子，每个不对称碳原子的绝对构型是和；或者，如果存在双键的话，那么将给出顺式和反式几何异构体。

For 2,2,4,4-tetrachloropentane,the energy of the conformer with gauche-gauche arrangement is lower; For 2,2,4,4,6,6-hexachloroheptane,the conformer with trans-gauche-trans-gauche arrangement is stable.

结果表明，对于2，2，4，4-四氯戊烷，采用gauche-gauche排列的旋转异构体的能量较低；2，2，4，4，6，6-六氯庚烷旋转异构体中，采用trans-gauche-trans-gauche排列的构象能量较低。

Then, have explored the conformer interconversion among all glycine conformers, and discussed some arguments about glycine conformers' symmetries.

研究所有的苷氨酸构象异构体之间相互转换，并且探讨了苷氨酸构象异构体的对称性问题。

1H NMR spectroscopic analysis of aromatic protons combined with theoretical analysis of molecular structures proved the existence of two rotational isomers at 300 K, as well as a rapid interconversion equilibrium at 330 K for both compounds Ⅰ and Ⅱ. However, only one conformer exists for compound Ⅲ and puerarin containing 7-phenolic hydroxyl instead of propyl in A-ring as the case of compounds Ⅰ and Ⅱ. Based on UV-Visible absorption data of neutral and basic solutions, and on the density function calculations, the 7-phenolic hydroxyl group in A-ring was found to be more acidic than the 4'-phenolic hydroxyl group in B-ring. The mechanism of derivation reaction and the structure-reactivity relationship of puerarin as an antioxidant were further discussed.

其中7-丙基葛根素Ⅱ属于新型取代衍生物；变温1H NMR和理论计算结果表明，在300 K时，葛根素和4'-丙基葛根素以单一构型存在；而7，4'-二丙基葛根素和7-丙基葛根素则存在两种核磁可分辨的旋转异构体，当温度升至330 K时，两种异构体可以相互转化；通过对比分析葛根素及其衍生物脱质子产物的紫外可见吸收光谱并结合理论计算，确定了A环上7位酚羟基比B环上4'位酚羟基先脱去质子，并由此进一步阐明了葛根素衍生化反应机理以及在抗氧化作用中可能的活性位点和结构活性关系。

In chapter 6, seven pairs of diastereoisomers of podophyllum lignans at C4-position, including three pairs of spin labeled compounds, were separated by MEKC with 20mM sodium tetraborate-30mM SDS-10％ 2-propanol (pH=9.5-9.7) within 20min.

第六章：首次利用胶束电动毛细管色谱分离了七对抗癌药物鬼臼类木脂素在C4位的差向异构体，该方法可用来鉴定分析物的纯度、确定自旋标记化合物C4-H的构型等，为研究差向异构体不同的抗癌机制提供检测手段。

In addition nC〓, nC〓, two isomers of C〓 sterene and three isomers of C〓 isoprenoid hydrocarbons were also identified from aliphatic fraction of pyrolyzed product at 200℃. After pyrolyzed at 300℃, the main aliphatic hydrocarbons were normal alkanes ranged from C〓 to C〓, with C〓 as the main peak and C〓 as the second main peak. Meanwhile, pristane, phytane and C〓 sterane were also detected. In the pyrolysates at 400℃ and 500℃, the content of saturated hydrocarbons decreased, the range of normal alkanes distribution became narrow and the main peak was nC〓. Low concentration of C〓-C〓 steranes was detected and the content of C〓-C〓 increased more.

在200℃热模拟产物饱和烃馏分中除检测出两种长链烯烃外，还检测到正十九碳单烯烃、正三十五碳双烯烃、两个碳二十八甾烯的同分异构体和三个C〓类异戊二烯烷烃化合物同分异构体。300℃模拟产物饱和烃主要为正烷烃，正烷烃的碳数分布范围为C〓-C〓，以C〓为主峰、C〓为次主峰；另外，样品中还检出姥鲛烷、植烷和C〓甾烷等化合物。400和500℃热模拟产物中的饱和烃含量下降，正烷烃系列碳数分布范围变窄，主峰碳后移至C〓，检测到低浓度的C〓-C〓甾烷系列化合物，另外，C〓-C〓藿烷系列化合物含量进一步增加。

The ground-state structures of 8 tautomers of cytosine were fully optimized at B3LYP/6-311+G(superscript **) level, and the tautomerism of 6 relatively stable tautomers of cytosine was studied.

用该方法对胞嘧啶分子的8种异构体构型进行了充分优化，研究了其中能量较低的6种胞嘧啶异构体的互变异构化过程。

Analyzed the relative stability and isomerization, it was found that Ni3BPsuperscript (3 was thermodynamically the most stable one. In addition, Ni3BPsuperscript (1, Ni3BPsuperscript (1 with singlet state and Ni3BPsuperscript (3, NiPsuperscript (3 with triplet state are kinetically stable ones.

分析各异构体的相对稳定性及异构化过程得出：Ni3BP上标(3是单、三重态中热力学最稳定的异构体；单重态的Ni3BP上标(1、Ni3BP上标(1和三重态的Ni3BP上标(3、Ni3BP上标(3具有一定的动力学稳定性。

Monosaccharide Isomerization Simple aldoses and ketoses containing the same number of carbon atoms are isomers of each other; that is, a hexose and a hexulose both have the empirical formula (C6 H1206 )and can be interconverted by isomerization.

单糖异构化含有相同数目碳原子的单醛糖和酮糖互为同分异构体，也就是说一个已醛糖和一个已酮糖都符合经验分子式C6 H1206，并且可通过异构化作用相互转化

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。