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The degenerate Cope Rearrangement in 2,6‐Barbaralanedicarbonitrile
Author(s) -
Jackman Lloya M.,
Ibar Gazanfer,
Freyer Alan J.,
Görlach Yvonne,
Quast Helmut
Publication year - 1984
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.19841170504
Subject(s) - chemistry , tautomer , dichloromethane , valence (chemistry) , degenerate energy levels , cope rearrangement , molecule , spectral line , atmospheric temperature range , crystallography , stereochemistry , organic chemistry , solvent , thermodynamics , physics , quantum mechanics , astronomy
The 1 H and 13 C NMR spectra of 4‐bromo‐2,6‐barbaralanedicarbonitrile ( 2b ) were completely analysed and the molecule is shown to exist as a single valence tautomer. The 13 C chemical shifts of 2b serve as estimates of the analogous shifts in the non‐exchanging valence tautomer of 2,6‐barbaralanedicarbonitrile ( 2a ) itself. The barrier for the degenerate Cope rearrangement of 2a in [D 2 ]dichloromethane has been determined from line width measurements in the temperature range 204 – 249 K to be δ G 206 † = 24.2 kJ. mol –1 . The solid state 13 C NMR spectrum of 2a indicated that the bulk of the sample is not undergoing rapid rearrangement at room temperature.