The immense acidifying effect of the supersubstituent NSO<sub>2</sub>CF<sub>3</sub>on the acidity of amides and amidines of benzoic acids in acetonitrile
作者:Lev M. Yagupolskii、Vitalij N. Petrik、Natalia V. Kondratenko、Lilli Sooväli、Ivari Kaljurand、Ivo Leito、Ilmar A. Koppel
DOI:10.1039/b204172c
日期:——
The pKa values of acidic dissociation of the conjugate acids of derivatives of benzoate anions, where one or two oxygen atoms are replaced by an NSO2CF3 group, N-aroyltrifluoromethanesulfonamides 1a–f and previously unreported N,N′-bis(trifluoromethylsulfonyl)benzamidines 4a–f, were measured in acetonitrile. In the case of the parent compound, the incorporation of the first NSO2CF3 group instead of the oxygen atom leads to a sharp (by 9.6 pKa units) increase in the acidity, whereas the replacement of the second oxygen atom results in a further huge increase in the acidity by 4.9 powers of ten. It was found that the sensitivity of the reaction series under consideration towards substituent effects (in the benzene ring) decreases in the following order: benzoic acids > benzamides (1a–f) > benzamidines (4a–f). The results of this work carry potentially important implications for the design of new types of superacids and catalytic materials.
在乙腈中测量了苯甲酸阴离子衍生物(其中一个或两个氧原子被一个 NSO2CF3 基团取代)、N-芳酰基三氟甲基磺酰胺 1a-f 和以前未报道过的 N,N′-双(三氟甲基磺酰基)苯甲脒 4a-f 的共轭酸的酸性解离 pKa 值。在母体化合物中,取代氧原子而加入第一个 NSO2CF3 基团会导致酸度急剧增加(增加 9.6 pKa 单位),而取代第二个氧原子则会导致酸度进一步大幅增加 4.9 的十次方。研究发现,所研究的反应系列对(苯环上的)取代基效应的敏感性按以下顺序递减:苯甲酸 > 苯甲酰胺(1a-f) > 苯甲酰胺(4a-f)。这项工作的结果对设计新型超酸和催化材料具有潜在的重要意义。