The rate and equilibrium constants for the formation of the Meisenheimer-type adducts from some 2-methoxy-3-nitro-5-X-thiophenes and sodium methoxide in methanol have been measured at various temperatures. The absence of linear correlation between log Ke, or log k1 and σp– constants has been interpreted in the light of the hyper-ortho relation in the thiophene ring. 13C N.m.r. chemical shifts for substrates
在各种温度下,已经测量了由
2-甲氧基-
3-硝基-5-X-
噻吩和
甲醇钠在
甲醇中形成迈森海默型加合物的速率和平衡常数。log K e或log k 1与σp –常数之间不存在线性关系,这是根据
噻吩环中的超正态关系来解释的。还确定了底物(1a–g)和相关的宝石-二甲
氧基加合物(2a–g)的13 C Nmr
化学位移。热力学与l3的比较C nmr数据表明,大多数研究的取代基主要是通过稳定环的C-5上的部分负电荷来促进加合物的形成。