H+BrCH_3体系反应动力学的准经典轨迹研究

本文在推广LEPS势能面上用准经典轨迹理论方法计算了20000条碰撞轨迹,得到各种散射通道的几率和速度常数,讨论了振动增强、通道竞争、振动绝热性、质量组合及角动量耦合等重要动力学效应,并建立了它们与势能面性质之间的联系。据此判断该反应按直接型回弹机理进行并可满意地解释交叉分子束实验观测到的不对称性产物角分布。     

多原子反应体系的高精度拟合势能面

本文介绍了近几年来我们组构建多原子反应体系的高精度拟合势能面的进展。我们基于神经网络(NN)方法,成功构建了多原子气相分子体系和气相分子在金属表面解离的一系列势能面。这些势能面的拟合精度相当高,并且经过了严格的量子动力学测试,能广泛应用到动力学研究中。我们还提出了一种新的置换不变势能面的拟合方法,即基本不变量神经网络方法(FI-NN)。基本不变量的使用极大地减少了神经网络输入层多项式的个数,有效提高了势能面的计算速度。     

化学反应的高精度从头算势能面

势能面是化学反应动力学研究的基础。近年来随着理论方法的发展与计算技术的进步,不但含三、四个原子反应体系的电子基态势能面的构建精度进一步提高,一些反应体系的多电子态耦合势能面的构建和含六个原子以上反应体系的高维从头算势能面的构建也取得了重要进展。本文结合若干典型体系势能面的构建工作,主要介绍了高精度电子基态势能面,包括Renner-Teller、旋轨耦合等非绝热效应的耦合势能面以及高维势能面方面的研究进展。     

基于神经网络的分子体系势能面构造

本文介绍了近年来使用神经网络构造分子体系势能面的进展,在以前的研究基础上完善了一套完整的分子构型选择方案,在严格的势能面评价标准下,完全解决了势能面构造过程中分子构型选择的难题.基于此方法,采用一系列拟合技巧,结合大量反应动力学计算,成功构造了一系列重要体系的高精度从头算势能面,并能得到可靠的化学动力学结果.     

Non-Condon电子转移速率理论与含时波包方法

随着电子转移理论在化学、材料科学、生物医学等领域的广泛应用,人们针对不同体系提出了多种电子转移理论模型。本文主要总结了近年来我们在non-Condon电子转移理论以及含时波包方法等方面的相关工作。首先阐述包含non-Condon效应的电子转移速率理论并用于二噻吩四硫富瓦烯有机半导体迁移率的计算。而后介绍了包含量子相干效应的含时波包方法,并初步用于研究二聚芴分子三三态能量转移过程。另外,本文还阐述了如何采用量子化学计算获得电子转移速率的结构参数。     

聚合物链构象的研究I: 1,2-聚丁二烯的构象分析

本文应用Flory的链分子统计理论研究1,2-聚丁二烯的链构象,选择固定键长和键角的分子模型,计算构象能,构成势能面图,并由势能面的构型积分,得到了表征1,2-聚丁二烯链构象特征的统计权重矩阵.     

聚合物链构象的研究 Ⅰ.1,2-聚丁二烯的构象分析

本文应用Flory的链分子统计理论研究1,2-聚丁二烯的链构象,选择固定键长和键角的分子模型,计算构象能,构成势能面图,并由势能面的构型积分,得到了表征1,2-聚丁二烯链构象特征的统计权重矩阵.     

OCS电子基态势能面与振动光谱的理论研究

本文采用键长-键角内标系下的自洽场-组态相互作用方法精确计算了OCS分子的振动高激发态能级,并结合实验观测到的振动能级利用非线性最小二乘法优化电子基态势能函数中的势能参数。由优化所得的势能面计算出的振动激发态能级与50个实验观测到的振动能级比较,标准偏差为0.08cm^-^1。此外,还用该势能面计算了OCS同位素分子的振动能级,计算结果与实验值也十分吻合。     

含时波包法研究RbI光电子能谱的脉冲延迟效应

利用含时波包方法模拟不同泵浦-探测延迟时间下RbI分子1+3多光子电离时间分辨光电子能谱(TRPES). 模拟过程同时考虑了三光子电离过程和自电离过程. 计算结果表明, 泵浦-探测延迟时间的改变会影响光电子能谱(PES)的形状, 而这种影响实质上是由于强场的存在改变了相关势能面的位置以及势能面之间的交叉所导致的.     

化学反应中的几何相效应

锥形交叉可以通过几何相效应影响核动力学.在过去的一些年里关于锥形交叉的理论有大量的发展和进步,本文综述了分子反应动力学领域针对几何相效应研究的一些理论成果.介绍了分子反应动力学中与几何相效应直接相关的一些最新成果,同时也对这些重要结果进行了解释.我们相信几何相效应将会在非绝热化学中发挥最重要的作用.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.