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The Influence of Polar and Steric Effects on the Selectivity of the β‐Cleavage of Alkyl Radicals
Author(s) -
Klenke Kurt,
Metzger Jürgen O.,
Lübben Stefan
Publication year - 1988
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.198811681
Subject(s) - steric effects , chemistry , alkene , radical , alkyl , cleavage (geology) , polar , selectivity , medicinal chemistry , stereochemistry , methyl group , organic chemistry , catalysis , materials science , physics , astronomy , fracture (geology) , composite material
Besides the generally dominating influences of product stability , also polar and steric effects must be taken into account when considering the β‐cleavage of alkyl radicals. In the example given here the steric effect of the methyl substituents results in the thermodynamically more stable alkene 1a (at 400°C) being formed in only slight‐excess compared to the alkene 2a . Normalized to the number of cleavable methyl groups, the methyl radical is even preferentially cleaved from the lesser substituted alkyl group! ( [2a]/[1a] ) norm =2.3 R = ( c C 6 H 11 ).