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Zur Energiedelle von Diradikalen, VIII . Das Energieprofil der entarteten Methylencyclobutan‐Umlagerung
Author(s) -
Roth Wolfgang R.,
Paschmann Volker
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960813
Subject(s) - chemistry , diradical , enthalpy , recombination , degenerate energy levels , standard enthalpy change of formation , standard enthalpy of formation , computational chemistry , excited state , thermodynamics , atomic physics , physics , quantum mechanics , gene , singlet state , biochemistry
On the Energy Well of Diradicals, VIII Part VII: Ref. . – Energy Profile of the Degenerate Methylenecyclobutane Rearrangement From the temperature and oxygen dependence of the trapping rates of the diradicals 4 and 6 , recombination enthalpies of 4.7 and 1.8 kcal · mol −1 are derived. These enthalpies agree well with estimates from our reaction force field (5.5 and 2.0 kcal · mol −1 ). The increasing stereoselectivity in the methylenecyclobutane rearrangement 1a → 1b with electronically less stabilizing substituents (R = Ph, CH 3 ) is related to the decreasing recombination enthalpy of the intermediate diradical 2 . This finding can be rationalized from the changing curve of the electronic energy during the recombination.