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本研究用集团结构适应性理论探讨了Cl~-+CH_3I反应在十一种质子溶剂和极性非质子溶剂中的溶剂效应机理。实验表明,亲核试剂Cl~-越游离,反应速率就越大。按集团结构适应性理论,一个良好的溶剂应同时具备下述两种集团结构:(1)强负电集团,以便栓住正离子M~+,使Cl~-游离;(2)带有一定量的正电荷的正电集团,而且电荷又较分散,这有助于Cl~-从M~+的束缚中解脱出来,使Cl~-更游离。如DMF和DMSO等极性非质子溶剂就是具有上述两种集团结构的优良溶剂。若溶剂正电集团过强或正电荷高度集中,则正电集团又抑制了Cl~-的进攻能力。因此能与Cl~-形成氢键的质子溶剂是不良溶剂。
In this study, the solvent effect mechanism of Cl ~ - + CH_3I reaction in eleven protic solvents and polar aprotic solvents was investigated using the theory of group structure adaptability. Experiments show that the more free the nucleophilic reagent Cl ~ -, the greater the reaction rate. According to the theory of group structure adaptability, a good solvent should have the following two kinds of group structure: (1) strong negative group, in order to plug positive ions M ~ +, Cl ~ - free; (2) with a certain amount of Positive charge of the positive group, and the charge is more dispersed, which helps Cl ~ - from the bond from M ~ + liberated, Cl ~ - more free. Polar aprotic solvents such as DMF and DMSO are good solvents with both of the above group structures. If the solvent positive group is too strong or positive charge is highly concentrated, the positive group also inhibited the Cl ~ - offensive capability. Therefore, proton-containing solvents capable of forming hydrogen bonds with Cl ~ - are poor solvents.