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271.
合成了β-芳氧基丙酸芳酯及β-芳氧基丙酰芳胺等17种化合物,经IR,UV,HNMR和元素分析确定了它们的结构,并对它们的生物活性进行了初步考察。 相似文献
272.
273.
The complexes PtRu(5)(CO)(15)(PMe(2)Ph)(mu(6)-C) (2), PtRu(5)(CO)(14)(PMe(2)Ph)(2)(mu(6)-C) (3), PtRu(5)(CO)(15)(PMe(3))(mu(6)-C) (4), PtRu(5)(CO)(14)(PMe(3))(2)(mu(6)-C) (5), and PtRu(5)(CO)(15)(Me(2)S)(mu(6)-C) (6) were obtained from the reactions of PtRu(5)(CO)(16)(mu(6)-C) (1) with the appropriate ligand. As determined by NMR spectroscopy, all the new complexes exist in solution as a mixture of isomers. Compounds 2, 3, and 6 were characterized crystallographically. In all three compounds, the six metal atoms are arranged in an octahedral geometry, with a carbido carbon atom in the center. The PMe(2)Ph and Me(2)S ligands are coordinated to the Pt atom in 2 and 6, respectively. In 3, the two PMe(2)Ph ligands are coordinated to Ru atoms. In solution, all the new compounds undergo dynamical intramolecular isomerization by shifting the PMe(2)Ph or Me(2)S ligand back and forth between the Pt and Ru atoms. For compound 2, DeltaH++ = 15.1(3) kcal/mol, DeltaS++ = -7.7(9) cal/(mol.K), and DeltaG(298) = 17.4(6) kcal/mol for the transformation of the major isomer to the minor isomer; for compound 4, DeltaH++ = 14.0(1) kcal/mol, DeltaS++ = -10.7(4) cal/(mol.K), and DeltaG(298) = 17.2(2) kcal/mol for the transformation of the major isomer to the minor isomer; for compound 6, DeltaH++ = 18(1) kcal/mol, DeltaS++ = 21(5) cal/(mol.K) and DeltaG(298) = 12(2) kcal/mol. The shifts of the Me(2)S ligand in 6 are significantly more facile than the shifts for the phosphine ligand in compounds 2-5. This is attributed to a more stable ligand-bridged intermediate for the isomerizations of 6 than that for compounds 2-5. The intermediate for the isomerization of 6 involves a bridging Me(2)S ligand that can use two lone pairs of electrons for coordination to the metal atoms, whereas a tertiary phosphine ligand can use only one lone pair of electrons for bridging coordination. 相似文献
274.
Guo‐Fu Chen Chang‐Heng Tan Zhu‐Lian Li Shan‐Hao Jiang Da‐Yuan Zhu 《Helvetica chimica acta》2003,86(3):787-792
Pseudolarolides O ( 1 ) and P ( 2 ), two novel triterpenoids with a cycloartane‐type framework, were isolated from the seeds of Pseudolarix kaempferi Gord. (Pinaceae). Their structures were elucidated as (16R,23S,25R)‐16,23‐epoxy‐3,4 : 9,10‐disecocycloartan‐1(10),9(11)‐diene‐3(4),26(23)‐diolide ( 1 ), and (9S,16R,23S,25R)‐1,9 : 16,23‐diepoxy‐8,9 : 9,10‐disecocycloartan‐1(29),5(6),10(19)‐triene‐3(4),26(23)‐diolide ( 2 ), respectively, on the basis of spectroscopic techniques and X‐ray‐diffraction studies. 相似文献
275.
本文报导用半经验方法研究N_1-氢-4-氨基-2-羰基胞嘧啶与4-亚氨基-2-羰基胞嘧啶异构化反应。用MINDO/3能量梯度法优化了孤立体系的全部自由度, 计算结果表明氨型比亚氨型稳定, △E=33.85 kJ mol~(-1); 限定分子体系在同一平面, 用Powell法优化过渡态几何构型, 计算所得正反应活化势垒为168.87 kJ mol~(-1), 逆反应活化势垒为135.02 kJ mol~(-1)。从IRC途径分析了该异构化反应的物理实质。 相似文献
276.
Considering the influences of electrostatic potential Phi upon the change of solute charge distribution deltarho and rho upon the change deltaPhi at the same time, a more reasonable integral formula of dG = (1/2) integral (V) (rhodeltaPhi + Phideltarho)dV is used to calculate the change of the electrostatic free energy in charging the solute-solvent system to a nonequilibrium state, instead of the one of dG = integral (V) PhideltarhodV used before. This modification improves the expressions of electrostatic free energy and solvation free energy, in which no quantity of the intermediate equilibrium state is explicitly involved. Detailed investigation reveals that the solvation free energy of nonequilibrium only contains the interaction energy between the field due to the solute charge in vacuum, and the dielectric polarization at the nonequilibrium state. The solvent reorganization energies of forward and backward electron transfer reactions have been redefined because the derivations lead to a remarkable feature that these quantities are direction-dependent, unlike the theoretical models developed before. The deductions are given in the electric field-displacement form. Relevant discussions on the reliability of theoretical models suggested in this work have also been presented. 相似文献
277.
Guang-Ju Chen Au-Chin Tang Xiao-Yuan Fu 《International journal of quantum chemistry》1992,43(5):713-723
An exact vibration–rotation kinetic energy operator for polyatomic molecules has been obtained on the basis of Sutcliffe's method, in terms of curvilinear internal coordinates and rotational angular moment operators. This operator is derived from the kinetic energy operator in Cartesian coordinates by the successive transformations using the chain rule. This kinetic energy operator can be used not only for the system of any triatomic and tetraatomic molecules and common polyatomic molecules in chemistry, but also for the investigation of the collision problems between two molecules after some modifications. Finally, using this Hamiltonian, the rotation–vibration coupling equations of polyatomic molecules have been derived and discussed. © 1992 John Wiley & Sons, Inc. 相似文献
278.
Summary A new stationary phase [bikis(2,6-di-O-pentyl-3-O-hex-6-enyl)-pentakis(2,6-di-O-pentyl-3-O-methyl)-β-CD-polysiloxane] was
synthesized and successfully applied in GC for the separation of chiral and achiral isomers. It possesses high column efficiency
and exhibits excellent separation ability for disubstituted benzenes. Some typical enantiomers and optical isomers are well
separated. The separation behavior of this new phase is characterized and discussed. 相似文献
279.
Wang Xiaolin Chen Yinliang Wang Xiuyuan Sun Ying Fu Yibei Guo Gaopin 《Journal of Radioanalytical and Nuclear Chemistry》1991,147(2):377-384
A method of determination of trace gold and iridium in steel is presented. The samples were preconcentrated with an anion exchanger. The chemical recoveries were determined by an isotope tracer technique using198Au and192Ir. 相似文献
280.
链酚胺型配体锌(Ⅱ)配合物模拟碳酸酐酶研究 总被引:1,自引:2,他引:1
合成了酚胺型链状配体,N,N'-二(2-羟基苄基)丙二胺(H~2L)及其Zn(Ⅱ)配合物(ZnL),通过元素分析、IR和^1HNRM等手段进行了表征。采用pH电位滴定法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,测定了配体的质子化常数以及配体与金属离子Zn(Ⅱ)配位反应平衡常数。讨论了配体与金属离子Zn(Ⅱ)的配位情况,得到了配位酚羟基的解离常数。运用分光光度法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,在pH=5.5~9.0(50mmol·dm^-^3缓冲溶液)范围内,研究了配合物作为碳酸酐酶模拟物催化对-硝基苯酚乙酸酯(NA)水解动力学,得到了NA酯水解的配合物催化速率常数k~N~P。实验结果表明,ZnHL^+的配位酚羟基的解离常数pK~a为6.83;催化速率常数k~N~P与pH之间不存在Sigmoidal型曲线关系,而是在pH值中性附近有最大值,ZnHL^+对NA酯水解有很好的催化效果,并且采取双重催化机理,是碳酸酐酶很好的模拟物。 相似文献