分子点群虚拟仿真实验的建设与实践*

结合结构化学课程中分子对称性知识点的教学,自主设计和开发了分子点群虚拟仿真实验(PGVL)平台,帮助学生深入认识理解分子对称性知识的重点和难点。该仿真实验采用Web技术构建,支持分子模型的显示和互动,使学生可以完成分子的各种对称操作、指出分子结构中的对称元素、推导分子点群及认识分子结构和性质之间的关系。PGVL在分子对称性教学中的应用,不仅完善了结构化学分子模型实践教学体系,而且提升了学生对结构化学课程的学习兴趣,丰富了结构化学实践教学内容,取得了良好的教学效果。     

Theoretical calculation of rate constants for the thermal isomerization from 1,2-butadiene to 1,3-butadiene

Ｔｈｅｉｎｖｅｓｔｉｇａｔｉｏｎｓｏｆｔｈｅｍｅｃｈａｎｉｓｍｓａｎｄｋｉｎｅｔｉｃｓｏｆｈｙｄｒｏｃａｒｂｏｎｐｙｒｏｌｙｓｅｓｐｌａｙａｋｅｙｒｏｌｅｉｎｅｌｕｃｉｄａｔｉｎｇｔｈｅｐｒｅｐａｒｔｉｃｌｅｓｏｏｔｃｈｅｍｉｓｔｒｙｐｈａｓｅ.Ｔｈｅｔｈｅｒｍａｌｉｓｏｍｅｒｉｚａｔｉｏｎｓａｒｅａｌｗａｙｓｉｎｖｏｌｖｅｄｉｎｔｈｅｓｅｐｙｒｏｌｙｓｉｓｍｅｃｈａｎｉｓｍｓ.Ｉｎｒｅｃｅｎｔｙｅａｒｓ,ＫｅｒｎａｎｄＳｉｎｇｈ[1]ａｎｄＨｉｄａｋａｅｔａｌ.[2,3]ｉｎｖｅｓｔｉｇａｔｅｄｔｈｅｍｅ…     

晶界对庞磁电阻颗粒薄膜的磁学和输运性能的影响

采用脉冲电子束沉积技术，在Si(100)单晶衬底上沉积庞磁电阻La_0.67Ca_0.33MnO₃颗粒薄膜，并对它的磁学性能和电学输运性能进行了表征.研究晶界对庞磁电阻薄膜的物理性能的影响，结果表明，晶界的存在使得晶粒之间的耦合变弱，在变温磁化过程中表现出团簇玻璃态行为，金属—绝缘体转变温度(T_p)远远低于铁磁—顺磁转变温度(T_c).低温下电子输运具有弱局域化行为.在低磁场下，晶界的存在掩盖了La_0.67Ca_0.33MnO₃的本征磁电阻行为. 关键词： 脉冲电子束沉积 晶界 磁学和电学输运性能 庞磁电阻     

运用生存模型对上证指数与成交量的研究——兼论股市的政策效应

本文首次运用生存模型对上证指数连续涨跌进行了研究,发现连涨和连跌的股指服从Gamma分布,当股指涨跌在不同的范围时其后下跌和上海的概率是不同的。我们还讨论了股指与成交量的关系。通过对各生存函数的分析,我们阐述了"T+1"政策和"涨停板"政策对股指产生的政策效应。     

运用生存模型对上证指数涨跌天数的研究

本运用生存模型对上证指数连续上涨和下跌天数进行了研究,分析了“T 1”政策和“涨停板”政策对股市的影响。我们发现生存模型对于分析股市的变动是有效的。     

捷联惯导系统算法比较研究

运用四子样圆锥补偿现代捷联惯导系统姿态算法、针对船舶的摇摆运动在数字信号处理芯片（DSPs)上进行了仿真，并与三子样圆锥补偿算法，三子样等效转动矢量法和单子样毕卡逼近法的仿真，并与三子样圆锥补偿算法、三子样等效转动矢量法和单子样毕卡逼近法的仿真结果进行了比较。结果表明：四子样圆锥补偿能更有效地抑制不可交换误差，提高姿态精度，且整个导航算法在TMS320C6211 EVM仿真器上运行，所花时间为5．3毫秒。     

固相不对称合成的一些进展

近年来,随着液相不对称合成方法在固相条件下的成功实现,固相不对称合成将成为构建手性小分子库和天然产物全合成的有力工具。本文综述了近年来通过底物手性诱导、手性辅助物诱导、手性试剂诱导和手性催化诱导的固相不对称合成的研究及应用,并探讨了其今后的发展方向。     

Ab initio study on the mechanism of rhodium-complex- catalyzed carbonylation of methanol to acetic acid

The whole catalytic cycle of the carbonylation of methanol to acetic acid catalyzed by Rh complex is theoretically studied. All structural geometries of reactant, intermediates, transition states and product are optimized at HF/LANL2DZ level under the ECP approximation. The potential energy profiles for elementary reactions of carbonylation are calculated respectively. The transition states are further confirmed by having one and only one imaginary vibrational frequency. The results indicate that the activation energy values of CH3I oxidative addition, carbonyl insertion and CH3COI reductive elimination fundamental steps are 216.03, 128.10 and 126.55 kJ/mol, respectively; and that the CH3I oxidative addition step is predicted to be the rate-determining one.     

羟基钴催化氢甲酰化反应的理论研究

采用有效核势能近似(ECP)从头算方法,在HF/LANL2DZ水平下研究了羰基钴催化的氢甲酰化反应循环中的羰基插入、H2 氧化加成和脱氢还原系列基元反应步骤的反应机理.优化得到了反应基态势能面的中间体、过渡态和产物的几何构型.计算了反应活化位垒,并对各过渡态进行了振动分析以确认.理论计算结果表明,羰基插入、H2 氧化加成、脱氢还原的基元反应步骤的活化位垒分别为67.79、139.11和44.78kJ·mol-1.     

Theoretical investigation on regioselectivity of aromatic ketones in the addition with olefin catalyzed by RuH2(CO)(PPh3)3

Ab initio method is employed to study the structures of twelve aromatic ketones at HF/3-21G, HF/6-31G and HF/6-31G levels, respectively. A theoretical analysis is also carried out to study the regioselectivity and reactivity of aromatic ketones in the addition with olefin catalyzed by RuH2(CO)(PPh3)3. The results indicate that a U shape LUMO conjugation of aromatic ketones in a plane plays an important role in regioselectivity on the cleavage of p C-H bond and is a nec-essary factor to success of addition with olefin, and that sterle effect is an indispensable factor in forming additional ortho-product. Meanwhile, electronic effect may influence the rate of addition for the structures alike which only have different replacements in the same site of aromatic ring, such as furan, thiophene and pyrole. A possible catalytic reaction mechanism is proposed that the addition of C-H bond may be carried out by a coordination of aromatic ketones with Ru complex.