Base catalysis in nucleophilic aromatic substitution reactions: evidence for cyclic transition state mechanism over the dimer mechanism in a non-polar aprotic solvent
作者:Olayinka Banjoko、Chike Ezeani
DOI:10.1039/p29860000531
日期:——
The reactions of X-phenyl 2,4,6-trinitrophenyl ethers [X = 2-NO2, 3-NO2, 4-NO2, 2,4-(NO2)2, 3,4-(NO2)2, 2,5-(NO2)2, and 2,6-(NO2)2] with aniline in benzene display three distinct mechanisms even though all except the 2,6-dinitrophenyl ether are base catalysed. The catalysis of the mononitro-substituted ethers involves two aniline molecules and proceeds at a temperature-independent rate in the temperature
X -苯基-2,4,6-三硝基苯醚[的反应X = 2-NO 2,3-NO 2,4-NO 2,2,4-(NO 2)2,3,4-(NO 2)2,2,5-(NO 2)2,和2,6-(NO 2)2]与苯胺在苯中的反应显示出三种不同的机理,尽管除2,6-二硝基苯基醚以外的所有碱均被催化。一硝基取代醚的催化反应涉及两个苯胺分子,并且在5–35°C的温度范围内以与温度无关的速率进行,而二硝基取代醚的催化仅涉及一个苯胺分子,并且以与温度无关的速率进行在相同温度范围内。根据涉及过渡状态的四元,六元和八元环的循环机制来解释结果。