Ph(2-furyl)CH2, 29.6; (2-thienyl)2CH2, 27.1. The effect of the 2-Cl substituent in the thiophen ring is close to that of the p-Cl substituent in the benzene ring, and the effects of the p-Me substituents on the benzene ring are very close to those of the 2-Me substituents on the thiophen or furan rings. The product and rate isotope effects (determined by use of MeOD) are consistent with separation of the
已确定(2-
噻吩基)2 CHSiMe 3和化合物Ph(2-
噻吩基)CHSiMe 3和Ph(2-
呋喃基)CHSiMe 3及其某些衍
生物在25°C下的NaOMEMeOH在25°C的裂解速率。在苯基的m-或p-位或杂环基的5-位上的取代基。结果表明,2-
噻吩基和2-
呋喃基比苯基更有效地稳定了碳负离子中心,并且可以得出以下近似的p K a值:Ph 2 CH 2,33.4; n 2 =1。pH值(2-
噻吩基)CH 2,30.0; pH值(2-
呋喃基)CH 2,29.6; (2-
噻吩基)2 CH 2,27.1。
噻吩环中2-Cl取代基的作用与苯环中p -Cl取代基的作用接近,苯环中p -Me取代基的作用与2-Me取代物的作用非常接近
噻吩或
呋喃环上的取代基。产物和速率同位素效应(通过使用MeOD确定)与速率确定步骤中碳负离子的分离是一致的。