The 13C n.m.r. chemical shifts of some 4- and 5-substituted thiophene-2-carboxylic acids and of the corresponding anions have been measured in methanol. The observed substituent chemical shifts have been compared with the calculated values and then analysed according to single and dual substituent parameter linear free energy relationships. The results have been rationalized in terms of separate resonance
已经在
甲醇中测量了一些4-和5-取代的
噻吩-2-
羧酸以及相应的阴离子的13 C nmr
化学位移。已将观察到的取代基
化学位移与计算值进行比较,然后根据单和双取代基参数线性自由能关系进行分析。就取代基效应的独立共振和感应贡献而言,结果已得到合理化。共振项表明在环与羧基之间不发生共轭。