Solvent effects on ion pairing of tetra‐n‐butylammonium cyanide. A conductometric study
Solvent effects on ion pairing of tetra‐n‐butylammonium cyanide. A conductometric study
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溶剂对四正丁基氰化铵离子配对的影响电导研究。
DOI：
10.1002/poc.1305
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发表时间：
2008
影响因子：
1.8
通讯作者：
P. Beronius
中科院分区：
文献类型：
--
作者：
Susanna Macmillar;Yao;K. Westaway;O. Matsson;P. Beronius
本论文主要是利用动力学同位素效应研究反应机理。亲核双分子取代（SN 2）反应的研究有双重目的，提高我们的基本理解的分子反应性和评估动力学同位素效应的能力，作为机械工具。在四氢呋喃中的氰根离子和氯乙烷之间的SN 2反应的过渡态被发现是反应物一样，只是稍微紧比以前已经发现的相同的反应在二甲基亚砜。一个结论是，即使没有溶剂模型，理论计算也能很好地预测该反应中的过渡态结构。氰根离子与对位取代苄基氯的SN 2反应具有类反应物过渡态，其中Cα-Cl键受对位取代的影响最大.理论计算表明，如果过渡态中的键裂不太剧烈，氯离子的KIE可以作为Cα-Cl键上取代基效应的探针。此外，还测定了氰根离子与二甲基亚砜中各种乙基底物反应的亲核碳11 C/14 C KIE，并采用精密电导法测定了四丁基氰化铵在四氢呋喃和二甲基亚砜中的聚集状态，这对于在机理研究和合成反应中常用的亲核试剂具有重要意义.离子对形成的趋势被发现是非常轻微的，显着的，非常强的二甲基亚砜，水和四氢呋喃，分别。测定了单胺氧化酶B催化苄胺脱氨反应的氮动力学同位素效应，试图获得关于氧化机理的结论性证据。单胺氧化酶是与例如抑郁症和帕金森病的治疗有关的重要药物靶标，并且关于酶如何影响催化的知识将促进高度选择性和有效抑制剂的设计。
This thesis concerns the study of reaction mechanisms by means of kinetic isotope effects (KIEs). Studies of the nucleophilic bimolecular substitution (SN2) reaction had the dual purpose of improving our fundamental understanding of molecular reactivity and assessing the ability of kinetic isotope effects to serve as mechanistic tools. The transition state of the SN2 reaction between a cyanide ion and ethyl chloride in tetrahydrofuran was found to be reactant like and only slightly tighter than has been found previously for the same reaction in dimethyl sulphoxide. One conclusion was that the transition-state structure in this reaction was predicted fairly well by the theoretical calculations, even without solvent modelling. The SN2 reactions between cyanide ions and para-substituted benzyl chlorides were found to have reactant-like transition states, of which the Cα-Cl bond was most influenced by the para-substitution. Theoretical calculations indicated that the chlorine KIEs could be used as probes of the substituent effect on the Cα-Cl bond if bond fission was not too advanced in the transition state. Furthermore, the nucleophile carbon 11C/14C KIEs were determined for the reactions between cyanide ions and various ethyl substrates in dimethyl sulphoxide.Precision conductometry was employed to estimate the aggregation status of tetrabutylammonium cyanide in tetrahydrofuran and in dimethyl sulphoxide, which is of interest as tetrabutylammonium cyanide is frequently used as the nucleophilic reagent in mechanistic investigations and synthetic reactions. The tendency for ion-pair formation was found to be very slight, significant, and very strong in dimethyl sulphoxide, water, and tetrahydrofuran, respectively. The nitrogen kinetic isotope effect on monoamine oxidase B catalysed deamination of benzylamine was determined in an attempt to obtain conclusive evidence regarding the mechanism of the oxidation. Monoamine oxidase is an important drug target in connection with the treatment of, for example, depression and Parkinson’s disease, and knowledge on how the enzyme effects catalysis would facilitate the design of highly selective and efficient inhibitors.