2,3-二氰基-2,3-二(p—X苯基)丁二酸二乙酯类碳—碳键型引发剂

合成了2,3-二氰基-2,3-二(p—X苯基)丁二酸二乙酯(X=OCH_3,CH_3,Cl,H和NO_2),分离出它们的meso-和dl-异构体,分别对这些异构体的分子结构和构型进行了鉴定,测定了它们分子的中心C—C键均裂反应动力学及其对苯乙烯等的引发作用。     

无量纲参数法对络合反应化学平衡的研究

本文应用可逆反应的热静力学无量纲参数法,研究了二苯并-18-冠-6与金属钠离子在“800/200(V/V)”DMSO-H_2O混合溶剂中的络合反应。直接测定了反应的焓变和平衡常数,讨论了这种方法的适用范围,建立了测定平衡常数的相对误差表示式并提出了用外推法求K_(?)的基本要求。     

新型碳苷糖类维生素D_2衍生物的合成

以D-葡萄糖为原料,经碳苷化反应,酰化反应和脯氨酸-DIPEA催化的aldol反应制得2个碳苷糖[1-(4'-羟基苯基)-4-C-β-四乙酰基葡萄糖基-3-烯-2-酮(5a)和1-(3-羟基苯基)-4-C-β-四乙酰基葡萄糖基-3-烯-2-酮(5b)];5与琥珀酸维生素D2经Steglich酯化反应合成了2个新型碳苷糖类维生素D2衍生物,其结构经1H NMR,13C NMR和HR-ESI-MS表征。     

端基含36个己氧基偶氮苯基元的二代碳硅烷光致变色液晶树状高分子的光化学研究

研究了含36个己氧基偶氮苯介晶基元的二代(G2)光致变色液晶树枝状高分子在氯仿和四氢呋喃溶液中的最大吸收波长,摩尔消光系数,反顺光异构化反应速率常数,光化学回复异构化正逆反应速率常数及其平衡常数,G2和G1的光致变色反应速率常数kp为10-1s-1,而含偶氮基元光致变色液晶聚硅氧烷的kp为10-8s-1,因此液晶树状高分子的光响应速率比后者快107倍.     

四氢叶酸辅酶结构和性能的模拟及取代一碳单元转移反应的研究

本工作模拟了四氢叶酸辅酶的结构和反应性能, 合成了模型化合物碘化1, 2-二甲基-3-对甲氧苯磺酰基咪唑啉, 研究了模型化合物与单官能团亲核体、双官能团亲核体相作用, 以甲酸、甲醛氧化态转移取代一碳单元[≡C-CH~3, =C(CH~3)CH~2NO~2]的反应, 部分反应生成了咔啉类生物碱衍生物和其它杂环类化合物。     

基于氧化还原反应的配位平衡移动总反应平衡常数的推导

配位平衡的移动,可以遵从相同的“推导总反应的平衡常数”模式来做定性和定量的探讨。但在“氧化还原反应对配位平衡的影响”中,只是对化学反应做定性描述,总反应的平衡常数并没有推导,缺乏定量的探讨。原因在于氧化还原平衡常数与其他3大平衡常数不同,无法直接查得,需借助公式算出,具有隐蔽性,给总反应的推导造成了障碍。本文通过总反应平衡常数的推导解决了这个问题。     

碳硼烷和碳硼炔金属配合物中金属-碳键的化学性质

碳硼烷和碳硼炔金属配合物中的金属-碳键具有不同于经典金属-碳键的化学性质.一方面,二十面体碳硼烷独特的电子和空间效应使得碳硼烷金属配合物中的金属-碳键不参与和不饱和分子的反应 另一方面,在一定条件下具有大空间位阻的碳硼笼可以诱导某些碳-碳偶联反应.然而,碳硼炔金属配合物中的金属-碳键能与多种不饱和分子发生反应,其反应模式取决于中心金属离子的电子构型.本文简要总结了我们近期在这方面的研究进展.     

基于糖烯的碳苷合成方法研究进展

碳苷是一类具有多种生物活性的糖类天然产物,其独特的C—C糖苷键构筑是糖化学研究中的热点和难点.通过双键官能团构建新的C—C键是有机化学中的常用策略.随着烯化学的飞速发展,含1,2-位双键的糖烯供体在碳苷合成中也取得了显著进步.从FerrierI型碳苷化反应、Heck偶联型碳苷化反应、1-取代糖烯的过渡金属催化偶联碳苷化反应、2-取代糖烯的Michael加成型和自由基加成型碳苷化反应等方面,总结近年来基于糖烯的碳苷合成方法.     

水相体系中的碳碳成键反应

水是质子供体,又是质子受体,又因具有较大的疏脂性质,故在许多有机反应中水不宜作为溶剂使用。在某些反应体系中,微量水的存在就会使产率大为降低甚至完全不反应。因此无水要求常见于有机反应的实验过程。然而,近年来发现某些过去常在无水溶剂中进行的有机反应其实也可以在水溶剂体系中进行,且也能得到非常好的结果。下面举几个例子。     

Fe和Co催化的碳-碳偶联反应的最新进展

作为廉价而且低毒的金属, Fe和Co是发展催化剂的理想元素. 同时由于Fe和Co有着多种氧化还原价态, 它们的催化化学应该具有极其丰富的内容. 然而由于种种原因, Fe和Co的催化剂很少得到有机化学家的关注. 直到最近几年, 人们才发现Fe和Co的催化剂可以很好地催化碳-碳偶联反应. 综述了Fe和Co催化碳-碳偶联反应的条件、产率和选择性; 探讨了这些新奇反应的可能机理; 并介绍了这些反应在复杂化合物合成中的应用.     

配位化学中的直线自由能关系XXI: 铜(II)-13-取代苄基-1, 4, 8, 11-四氮杂环十四烷-12, 14-二酮配合物的生成及酸分解行为研究

采用pH法, 在25.0±0.1℃, I=0.1 mol.dm^-^3 (KNO3)条件下, 测定了13-取代苄基-1, 4, 8, 11-四氮杂环十四烷-12,14-二酮的质子化常数及其与Cu(II)配位的平衡常数。讨论了配体与金属离子的配位方式。在25.0±0.1℃, 离子强度为0.1mol.dm^-^3 (KNO3)下, 采用分光光度法, 研究了这些配体铜(II)配合物的酸分解动力学行为。探讨了配合物酸分解机理,得到了速控步的速率常数。发现配位反应平衡常数与配体的质子化常数及配合物酸分解反应速率常数之间存在较好的Hammett型和Bronsted型直线自由能关系。同时探讨了取代基对配合物生成及酸分解的影响情况。     

二硅烯异构化反应的理论研究, 从头等水平上的动力学, 热力学分析

本文在从头算水平上计算了二硅烯HXSi-SiH2(X=H,D)异构化反应的反应物、产物及过渡态构型的能量、谐振动频率和反应活化能等,又计算了反应的热力学函数变化, 平衡常数及速率常数, 结果表明,该异构化反应是放热的, 且可自发进行, 结论与Newman的实验事实相符合, 值得注意的是, 零点能校正对该异构化反应的计算有改进。     

Effects of Pressure, Solvent, and Substituenton the Thermal Isomerization of 2-Oxo-spiro［diazirine-3,3-indoline］

The kinetic effects of pressure, solvent, and substituent on the thermal isomerization from 2-oxospiro［diazirine-3,3-indoline］ to 3-diazo-2-oxo-indoline have been examined. The rate constants of the thermal isomerization increased with increasing external pressure and were related to the σ+P substituent constant of Hammett correlation. The results suggest that the thermal isomerization proceeds via a dipolar transition state involving heterolytic bond fission. However, the kinetic solvent effects on the thermal isomerization were not observed. The special solvent effects were discussed on the basis of the linear free energy relationship.     

Thermal isomerization of 5-methoxy-3-arylisoxazoles to methyl 3-aryl-2H-azirine-2-carboxylates

The thermal isomerization of 5-methoxy-3-arylisoxazoles to methyl 3-aryl-2H-azirine-2-carboxylates was subjected to a kinetic study. A correlation between the isomerization rate constants and the ⁺ constants of the substituents in the aromatic ring is observed. The enthalpies of formation of a number of isoxazoles and 2H-azirines were calculated. The effect of the nature of the substituents on the mutual isomerization of isoxazoles and azirines is discussed. The results make it possible to refute the approved and previously proposed diradical mechanism for the isomeric transformations and are in agreement with a nitrene mechanism for the formation of azirines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1053–1056, August, 1978.     

周边含己氧基的三代光致变色液晶树枝状大分子的光化学

报道了新化合物含108个己氧基端基的三代(G3)碳硅烷光致变色液晶树状大分子在溶液中的反-顺光异构化反应速率常数k_p, 光回复异构化正/逆反应速率常数k_t和k_c, 热回复异构化反应速率常数k_H, 光回复异构化反应平衡常数k_t/k_c, 活化能E, 异构转化率A/A₀及组分比A'/A₀. G3的光致变色反应速率常数的数量级为10^－1 s^－1, 而侧链含偶氮基元的光致变色聚硅氧烷的光致变色反应速率常数的数量级为10^－8 s^－1, 因此G3的光响应速率比后者快10⁷倍.     

Activation enthalpies and entropies for the microscopic rate constants of acetate-catalyzed isomerization of 5-androstene-3,17-dione

Both acetic acid and acetate catalyze the isomerization of 5-androstene-3,17-dione (1) to its conjugated isomer, 4-androstene-3,17-dione (3), through a dienol(ate) intermediate. The temperature dependence of the overall isomerization rate constants and of the microscopic rate constants for this isomerization was determined, and the Arrhenius plots give the activation enthalpy and entropy for each step. The source of the activation energy for the overall isomerization and for each of the individual steps is predominantly enthalpic, with a moderate to low entropic penalty. Additionally, the entropy and enthalpy for the keto-enol equilibrium of 1 and dienol were determined; this equilibrium is entirely controlled by enthalpy with no entropic contribution. The relevance of these results to the mechanism of the isomerization of 1 catalyzed by the enzyme 3-oxo-Delta(5)-steroid isomerase is discussed.     

Photoinduced face-inversion of conjugated tetraene ligands on a Pd-Pd-Pd moiety

The linear sandwich tripalladium complexes [Pd3{Ar(CH=CH)4Ar}2[BArf]2 (Ar = Ph, p-t-Bu-C6H4, p-styryl-C6H4) undergo photoinduced isomerization involving face-inversion of the tetraene ligands. Irradiation of these complexes with visible light (>510 nm) resulted in rac (staggered sandwich) to meso (eclipsed sandwich) isomerization. The structures of rac and meso isomers are determined by X-ray crystallographic analyses.     

Photochemical reaction kinetics in optically dense media: The influence of thermal reactions

The kinetics of photochemical reactions in optically dense media essentially free from diffusion was considered. The photochromic isomerization A ↔ B was studied as an example. If thermal isomerization is possible, a stationary state is achieved in time determined by rate constants for the thermal reactions. The concentration wave profile is changed during the photochemical reaction propagation. Low values of thermal reaction constants and decrease in sample optical density during photochemical isomerization were found to be essential for maximal wave penetration into the sample. Sharp concentration gradients of A and B can be observed when both the optical density is increased during photochemical isomerization and the quantum yield of the direct photochemical reaction A → B is higher than that of the reverse photochemical reaction B → A.     

High-pressure rate rules for alkyl + O2 reactions. 1. The dissociation, concerted elimination, and isomerization channels of the alkyl peroxy radical

The reactions of alkyl peroxy radicals (RO(2)) play a central role in the low-temperature oxidation of hydrocarbons. In this work, we present high-pressure rate estimation rules for the dissociation, concerted elimination, and isomerization reactions of RO(2). These rate rules are derived from a systematic investigation of sets of reactions within a given reaction class using electronic structure calculations performed at the CBS-QB3 level of theory. The rate constants for the dissociation reactions are obtained from calculated equilibrium constants and a literature review of experimental rate constants for the reverse association reactions. For the concerted elimination and isomerization channels, rate constants are calculated using canonical transition state theory. To determine if the high-pressure rate expressions from this work can directly be used in ignition models, we use the QRRK/MSC method to calculate apparent pressure and temperature dependent rate constants for representative reactions of small, medium, and large alkyl radicals with O(2). A comparison of concentration versus time profiles obtained using either the pressure dependent rate constants or the corresponding high-pressure values reveals that under most conditions relevant to combustion/ignition problems, the high-pressure rate rules can be used directly to describe the reactions of RO(2).     

高效液相色谱法研究二(烷基黄原酸)合钯(II)间的配体交换反应动力学

高效液相色谱法, 由于其分辨率高和检测浓度低, 在研究反应物和产物的结构和物理化学性质极为相似的反应中显示出独特的本领, 本文利用高效液相色谱法, 在12-32℃(研究了二(烷基黄原酸)合钯(II)间的配体交换反应动力学.