Abstract
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 pattern. For example, there is rate-acceleration not only by electron-withdrawing groups such as p-CF3 and p-Cl, but also by normally electron-releasing groups such as p-OMe and p-NMe2. For the para substituents, the effects are roughly in line with their σ1 constants.The analogy with base-catalysed aromatic hydrogen-exchange is discussed, and substituent effects in the two reactions are compared. An explanation previously advanced for the abnormalities in the hydrogen exchange is examined in the light of the results for the cleavage.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the Chemical Society B: Physical Organic
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
