Hydrogen-bonded nucleophile effects in ANS: the reactions of 1-chloro and 1-fluoro-2,4-dinitrobenzene with 2-guanidinobenzimidazole, 1-(2-aminoethyl)piperidine and<i>N</i>-(3-aminopropyl)morpholine in aprotic solvents
作者:Cecilia E. Silvana Alvaro、Alicia D. Ayala、Norma S. Nudelman
DOI:10.1002/poc.1712
日期:2011.2
e (3‐APMo) in toluene at 25 ± 0.2 °C were studied under pseudo first‐order conditions. For the reactions of 2‐GB carried out in pure DMSO, the second‐order rate coefficients were independent of the amine concentration. In contrast, the reactions of 2‐GB with DNFB in toluene, showed a kinetic behaviour consistent with a base‐catalysed decomposition of the zwitterionic intermediate. These results suggest
2,4-二硝基氟苯(DNFB)和2,4-二硝基氯苯(DNClB)与2-胍基苯并咪唑(2-GB)在40±0.2°C下在二甲亚砜(DMSO),甲苯和甲苯中的反应动力学– DMSO混合物,并带有1-(2-氨基乙基)哌啶(2-AEPip)和N在伪一级条件下研究了在25±0.2°C的甲苯中的(3-氨基丙基)吗啉(3-APMo)。对于在纯DMSO中进行的2 GB反应,二级速率系数与胺浓度无关。相反,2-GB与DNFB在甲苯中的反应显示出与两性离子中间体的碱催化分解相一致的动力学行为。这些结果表明在甲苯中2 GB的分子内氢键,在DMSO中不存在。为了证实这一解释,在DMSO-甲苯混合物中对反应进行了研究。少量的DMSO会显着提高速率,这是偶极非质子传递介质经典作用所无法预期的;效果与亲核试剂/助溶剂混合聚集体的形成一致。对于3-APMo与两种底物在甲苯中的反应,二级速率系数k A对[胺]表现出线性依赖性