Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The isodynamical interconversion between the quasiplanar equilibrium conformers 1b and 1c of 1,5-bisdehydroannulene requires a free energy of activation ΔG# = 4.5 ± 0.2 kcal/mol (120 K) which was determined by line shape analysis of its temperature-dependent NMR. spectrum. Force field calculations indicate that this barrier reflects the energy needed to disrupt the cyclic π-conjugation in going to the nonplanar transition state 1a.
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