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The Tris(trimethylsilyl)silane/Thiol Reducing System: A Tool for Measuring Rate Constants for Reactions of Carbon‐Centered Radicals with Thiols
Author(s) -
Chatgilialoglu Chryssostomos
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690221
Subject(s) - chemistry , trimethylsilyl , silylation , radical , hydrogen atom abstraction , reaction rate constant , decarbonylation , substituent , alkyl , silane , photochemistry , medicinal chemistry , aryl , organic chemistry , catalysis , kinetics , physics , quantum mechanics
An extension of the well‐known ‘free‐radical‐clock’ methodology is described that allows one to determine the rate constants of carbon‐centered radicals with a variety of thiols by using the tris(trimethylsilyl)silane/thiol couple as a reducing system. A total of 20 rate constants for the hydrogen abstraction from a variety of alkyl‐, silyl‐, and aryl‐substituted thiols by the primary‐alkyl radical 2 in toluene at 80° were determined with the aid of the 5‐ exo‐trig cyclization as a timing device. Further, seven rate constants for the hydrogen abstraction from a variety of alkyl‐ and silyl‐substituted thiols by the acyl radical 9 in benzene at 80° were measured using the decarbonylation process as a timing device. The rate constants varied over two orders of magnitude from 10 6 to 10 8 M −1 s −1 . Substituent effects were rationalized. The radical‐trapping abilities of these reducing systems and those of other common hydrogen donors were compared.