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Substituenteneffekte auf die CC‐Bindungsstärke, 10. Resonanzstabilisierung von Alkylradikalen durch zwei geminale Cyangruppen
Author(s) -
Pakusch Joachim,
Beckhaus HansDieter,
Rüchardt Christoph
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240535
Subject(s) - chemistry , geminal , radical , homolysis , bond dissociation energy , steric effects , dissociation (chemistry) , electron paramagnetic resonance , ground state , medicinal chemistry , bond cleavage , stereochemistry , photochemistry , crystallography , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics , catalysis
Effects of Substituents on the Strength of C–C Bonds, 10. – Resonance Stabilization of Alkyl Radicals by Two Geminal Cyano Groups The activation parameters of the homolytic cleavage of the C q – C q bonds of several dialkylated malonodinitriles ( 2 – 5 ) and of 1,1,2,2‐tetracyanoethane ( 7 ) and the heat of dissociation of 6 in solution have been determined. Together with the ground state strain of the radical precursors (obtained from the heats of combustion or EFF calculations) the steric influence on the dissociation process has been determined. The resonance stabilization energy of α,α'‐dicyanoalkyl radicals then calculated was (12.4 ± 0.9) kcal/mol. This result is discussed within the concept of capto‐dative stabilization. The destabilizing interaction of two geminal cyano groups is apparently the same in the ground state of 2 – 7 and the radicals generated from them.