The Tris(trimethylsilyl)silane/Thiol Reducing System: A Tool for Measuring Rate Constants for Reactions of Carbon-Centered Radicals with Thiols
✍ Scribed by Chryssostomos Chatgilialoglu
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- German
- Weight
- 125 KB
- Volume
- 89
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
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.