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Non‐Concerted Cope Rearrangement
Author(s) -
Roth Wolfgang R.,
Gleiter Rolf,
Paschmann Volker,
Hackler Ulrich E.,
Fritzsche Gerd,
Lange Holger
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199806)1998:6<961::aid-ejoc961>3.0.co;2-b
Subject(s) - chemistry , trapping , cope rearrangement , recombination , concerted reaction , activation barrier , ab initio , ab initio quantum chemistry methods , computational chemistry , interpretation (philosophy) , chemical physics , reaction mechanism , mechanism (biology) , density functional theory , stereochemistry , catalysis , molecule , physics , organic chemistry , ecology , biochemistry , quantum mechanics , biology , computer science , gene , programming language
Abstract The observation of practically identical activation parameters for the Cope rearrangement 2 → 6 and its “frustrated” counterpart 1 → 5 indicates a two‐step mechanism for the reaction 2 → 6 . Direct proof of this interpretation comes from trapping experiments, which demonstrate the intermediate formation of the diradicals 5 and 9 . From the temperature and oxygen dependences of the trapping rates, recombination barriers of Δ H ≠ = 11.5 and 6.5 kcal · mol −1 have been derived for 5 → 1 and 9 → 6 , respectively. These results agree well with ab initio calculations (CASPT2).