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The Equilibrium between Localized and Delocalized States of Thermochromic Semibullvalenes and Barbaralanes—Direct Observation of Transition States of Degenerate Cope Rearrangements
Author(s) -
Quast Helmut,
Seefelder Maximilian
Publication year - 1999
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/(sici)1521-3773(19990419)38:8<1064::aid-anie1064>3.0.co;2-u
Subject(s) - thermochromism , degenerate energy levels , delocalized electron , transition (genetics) , transition state , state (computer science) , condensed matter physics , physics , chemistry , quantum mechanics , mathematics , biochemistry , algorithm , gene , catalysis
The UV/Vis spectra of thermochromic semibullvalenes 1 and barbaralanes recorded at various temperatures yield enthalpy differences between the two degenerate classical structures 1 and 1′ and the less stable species ( 1* ) that absorb at long wavelengths. The latter species are interpreted in terms of higher, delocalized states that are located just above the flat potential energy barrier between the ground states (Δ H 0 =11 (R=H; in butyronitrile), 1 kJ mol −1 (R=Ph)).