二氯亚甲基锗烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.     

提高学生实验综合能力的有效途径

为了提高学生的实验能力,拓宽知识面,我们总结了多年教学实践经验,从 1987年开始,在对基础化学实验改革的同时,在二年级第 2学期期末集中 4周的时间为应化系的学生开设了一门新的实验课程———无机大制备实验。该课程经历了 10多年的不断改进,现在已形成一门完整的课程。这门新课程不仅强化了技能训练和操作规范,而且在培养学生的综合思维能力和处理实际问题能力方面,显示了独特的作用。　　对于综合性实验,设计理论及技巧方面是比较难的,大二学生所掌握的知识并不能完全独立地完成综合性实验的设计和实施,但在指导教师的参与下,学生通…