We have measured spectrophotometrically the rates of cleavage by aqueous methanolic alkali of the aryl–tin bonds in a series of X·C6H4·SnMe3 compounds. In this reaction, the rate-determining step of which probably involves separation of the carbanion X·C6H4–, the effects of meta substituents are in accord with the Hammett σ constants (σ= 2·18), but the effects of para substituents show an abnormal
我们通过分光光度法测量了一系列X·C 6 H 4 ·SnMe 3化合物中芳基-
锡键的
甲醇碱
水溶液的裂解速率。在该反应中,确定速率的步骤可能涉及分离碳负离子X·C 6 H 4 –,间位取代基的作用与Hammettσ常数(σ= 2·18)一致,但对位取代基显示异常图案。例如,不仅通过诸如p -CF 3和p -Cl的吸电子基团,而且通过诸如p -OMe和p -NMe 2。对于对位取代基时,效果大致与它们线σ 1周的常数。