Understanding the reaction mechanism of the regioselective piperidinolysis of aryl 1-(2,4-dinitronaphthyl) ethers in DMSO: Kinetic and DFT studies

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
Yasmen M. Moghazy, Nagwa MM Hamada, M. F. Fathalla, Yasser R. Elmarassi, Ezzat A. Hamed, Mohamed A. El-Atawy
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引用次数: 0

Abstract

Reactions of aryl 1-(2,4-dinitronaphthyl) ethers with piperidine in dimethyl sulfoxide at 25oC resulted in substitution of the aryloxy group at the ipso carbon atom. The reaction was measured spectrophotochemically and the kinetic studies suggested that the titled reaction is accurately third order. The mechanism is began by fast nucleophilic attack of piperidine on C1 to form zwitterion intermediate (I) followed by deprotonation of zwitterion intermediate (I) to the Meisenheimer ion (II) in a slow step, that is, SB catalysis. The regular variation of activation parameters suggested that the reaction proceeded through a common mechanism. The Hammett equation using reaction constant σo values and Brønsted coefficient value showed that the reaction is poorly dependent on aryloxy substituent and the reaction was significantly associative and Meisenheimer intermediate-like. The mechanism of piperidinolysis has been theoretically investigated using density functional theory method using B3LYP/6-311G(d,p) computational level. The combination between experimental and computational studies predicts what mechanism is followed either through uncatalyzed or catalyzed reaction pathways, that is, SB and SB-GA. The global parameters of the reactants, the proposed activated complexes, and the local Fukui function analysis explained that C1 carbon atom is the most electrophilic center of ether. Also, kinetics and theoretical calculation of activation energies indicated that the mechanism of the piperidinolysis passed through a two-step mechanism and the proton transfer process was the rate determining step.
二甲基亚砜中芳基1-(2,4-二硝基萘)醚的区域选择性胡椒醇分解反应机理:动力学和DFT研究
芳基1-(2,4-二硝基萘基)醚与哌替啶在二甲亚砜中于25℃下发生反应,导致芳基取代了对映碳原子。对该反应进行了光化学测量,动力学研究表明该反应准确地为三阶反应。其机理首先是哌啶在C1上的快速亲核攻击,形成两性中间体(I),然后两性中间体(I)脱质子生成Meisenheimer离子(II),这是一个缓慢的步骤,即SB催化。活化参数的规律变化表明,反应是通过一个共同的机制进行的。采用反应常数σo值和Brønsted系数值的Hammett方程表明,该反应对芳基取代基依赖性较差,反应具有明显的结合性和Meisenheimer类中间体。利用B3LYP/6-311G(d,p)计算水平,采用密度泛函理论方法对辣椒碱分解机理进行了理论研究。实验研究与计算研究相结合,预测了通过非催化或催化反应途径所遵循的机制,即SB和SB- ga。反应物的全局参数、所提出的活化配合物和局部福井函数分析说明,C1碳原子是醚的亲电性最强的中心。动力学和活化能的理论计算表明,哌啶醇解的机理为两步反应,其中质子转移过程为速率决定步骤。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
2.10
自引率
0.00%
发文量
5
审稿时长
2.3 months
期刊介绍: The journal covers the fields of kinetics and mechanisms of chemical processes in the gas phase and solution of both simple and complex systems.
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