Kinetics and Mechanism of Alkaline Hydrolysis of Y-Substituted Phenyl Phenyl Carbonates
摘要:
已通过光谱法测量了Y取代的苯基苯甲酸酯(2a-j)碱性水解的二级速率常数< T പി >$(k_{OH^-})$,并与先前报告的Y取代的苯基苯甲酸酯(1a-j)相应反应的< T പി >$k_{OH^-}$数值进行了比较。碳酸酯2a-j的反应性比苯酸酯1a-j高出8~16倍。Hammett图与< T Π >$\sigma^-$和< T Π >$\sigma^o$常数相关,但显示出许多散点,而Yukawa-Tsuno图则表现出良好的线性相关性,< T Π >$\rho$ = 1.21,< T Π >$\gamma$ = 0.33。因此,可以得出结论,该反应是通过一个协同机制进行的,其中脱离基团的排除仅稍微提前。然而,不能排除当前反应通过一个强迫协同机制及一个高度不稳定的中间体进行的可能性。
Kinetics and Mechanism of Alkaline Hydrolysis of Y-Substituted Phenyl Phenyl Carbonates
摘要:
已通过光谱法测量了Y取代的苯基苯甲酸酯(2a-j)碱性水解的二级速率常数< T പി >$(k_{OH^-})$,并与先前报告的Y取代的苯基苯甲酸酯(1a-j)相应反应的< T പി >$k_{OH^-}$数值进行了比较。碳酸酯2a-j的反应性比苯酸酯1a-j高出8~16倍。Hammett图与< T Π >$\sigma^-$和< T Π >$\sigma^o$常数相关,但显示出许多散点,而Yukawa-Tsuno图则表现出良好的线性相关性,< T Π >$\rho$ = 1.21,< T Π >$\gamma$ = 0.33。因此,可以得出结论,该反应是通过一个协同机制进行的,其中脱离基团的排除仅稍微提前。然而,不能排除当前反应通过一个强迫协同机制及一个高度不稳定的中间体进行的可能性。
Leaving-Group Substituent Controls Reactivity and Reaction Mechanism in Aminolysis of Phenyl Y-Substituted-Phenyl Carbonates
作者:Ji-Sun Kang、Yoon-Ju Song、Ik-Hwan Um
DOI:10.5012/bkcs.2013.34.7.2023
日期:2013.7.20
reported for the nucleophilicsubstitution reactions of phenyl Y-substituted-phenyl carbonates (5a-5k) with piperidine in 80 mol % /20 mol % DMSO at . The plots of vs. [piperidine] for the reactions of substrates possessing a strong electron-withdrawing group (EWG) in the leaving group (i.e., 5a-5i) are linear and pass through the origin. In contrast, the plots for the reactions of substrates bearing a weak
A Kinetic Study on Ethylaminolysis of Phenyl Y-Substituted-Phenyl Carbonates: Effect of Leaving-Group Substituents on Reactivity and Reaction Mechanism
作者:Yoon-Ju Song、Min-Young Kim、Ik-Hwan Um
DOI:10.5012/bkcs.2013.34.6.1722
日期:2013.6.20
A kinetic study on nucleophilicsubstitution reactions of phenyl Y-substituted-phenyl carbonates (5a-5j) with ethylamine in 80 mol % /20 mol % DMSO at is reported. The plots of vs. [amine] are linear for the reactions of substrates possessing a strong electron-withdrawing group (EWG) but curve upward for those of substrates bearing a weak EWG, indicating that the electronic nature of the substituent
报道了在 80 mol % /20 mol % DMSO 中,苯基 Y 取代的碳酸苯酯 (5a-5j) 与乙胺的亲核取代反应的动力学研究。对于具有强吸电子基团 (EWG) 的底物的反应,与 [胺] 的关系图是线性的,但对于具有弱 EWG 的底物的反应,曲线向上,表明离去基团中取代基 Y 的电子性质支配反应机理。根据取代基 Y 的性质,反应通过一种或两种中间体(两性离子四面体中间体及其去质子化形式)通过逐步机制进行。布朗斯特型图的分析和微观速率常数的剖析表明具有强 EWG 的底物的反应(例如,
Kinetic Study on Nucleophilic Displacement Reactions of Phenyl Y-Substituted Phenyl Carbonates with 1,8-Diazabicyclo[5.4.0]undec-7-ene: Effects of Amine Nature on Reaction Mechanism
作者:Kyoung-Ho Park、Min-Young Kim、Ik-Hwan Um
DOI:10.1002/bkcs.10627
日期:2016.1
constants (k N) for nucleophilic displacement reactions of phenyl Y‐substitutedphenyl carbonates (7a–7l) with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 oC have been measured spectrophotometrically. The Brønsted‐type plot for the reactions of 7a–7l with DBU is linear with βlg = –0.48, indicating that the reactions proceed through a concerted mechanism, which
A Kinetic Study on Nucleophilic Displacement Reactions of Phenyl Y-Substituted-Phenyl Carbonates with Alkali Metal Ethoxides: Metal Ion Effect and Reaction Mechanism
作者:Ik-Hwan Um、Ji-Yoon Seo、Ji-Sun Kang、Jun-Sung An
DOI:10.1246/bcsj.20120104
日期:2012.9.15
Pseudo-first-order rate constants (kobsd) have been measured for reactions of phenyl Y-substituted-phenyl carbonates with alkalimetal ethoxides (EtOM, M = Li, Na, and K). The plot of kobsd vs. [Et...
已经测量了苯基 Y 取代苯基碳酸酯与碱金属乙醇盐(EtOM,M = Li、Na 和 K)反应的伪一级速率常数 (kobsd)。kobsd vs. [Et...
Alkaline Hydrolysis of Y-Substituted Phenyl Phenyl Thionocarbonates: Effect of Changing Electrophilic Center from C=O to C=S on Reactivity and Mechanism
作者:Song-I Kim、Hey-Ran Park、Ik-Hwan Um
DOI:10.5012/bkcs.2011.32.1.179
日期:2011.1.20
not advanced in the RDS. Thus, alkaline hydrolysis of 4a-i has been concluded to proceed through a stepwise mechanism with formation of an intermediate being RDS, which is in contrast to the forced concerted mechanism reported for the corresponding reactions of 3a-i. Enhanced stability of the intermediate upon modification of the electrophilic center from C=O to C=S has been concluded to be responsible