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Primary alkyl radicals: Can they be persistent?
Author(s) -
Griller David,
Marriott Paul R.
Publication year - 1979
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550111103
Subject(s) - chemistry , radical disproportionation , steric effects , disproportionation , alkyl , radical , moiety , primary (astronomy) , medicinal chemistry , decomposition , beta scission , radical substitution , photochemistry , stereochemistry , organic chemistry , catalysis , physics , astronomy
The structure of t ‐Bu 3 SiċH 2 , (I), suggested that it might be a persistent primary alkyl radical since it has (i) a bulky group to protect the radical center; (ii) no β‐hydrogens, so that a radical‐radical disproportionation reaction is impossible; (iii) a β‐silicon atom, which should prevent β‐scission of tert ‐butyl as a unimolecular decomposition pathway. However, the self‐reaction of (I) in isooctane was found to be a diffusion controlled process with log( A / M −1 sec −1 ) = 10.7 ± 0.3 and E = 2.5 ± 0.2 kcal mole −1 . Hence (I) is not persistent and it is concluded that a persistent primary alkyl will only be observed when the—ĊH 2 moiety is deeply buried among sterically protecting groups.