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ESR. Spectra and Structures of Radical Anions in the Dibenzo[ a, e ]cyclooctene Series
Author(s) -
Gerson Fabian,
Martin William B.,
Plattner Georges,
Sondheimer Franz,
Wong Henry N. C.
Publication year - 1976
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19760590617
Subject(s) - chemistry , cyclooctatetraene , cyclooctene , molecule , ring (chemistry) , spectral line , ion , crystallography , radical , computational chemistry , stereochemistry , organic chemistry , catalysis , physics , astronomy
ESR. studies are reported for the radical anions of 5,6‐didehydro‐ and 5,6,11,12‐tetradehydro‐dibenzo[ a,e ]cyclooctene (III and IV, resp.), in addition to that of dibenzo[ a,e ]cyclooctene (II) itself, the spectrum of which has been reexamined. Comparison of the proton and 13 C coupling constants for II·⊖, III·⊖ and IV·⊖ indicates that the three radical anions do not differ greatly in their electronic and molecular structures. This statement implies that II·⊖ should also be substantially planar, i.e. , the tub‐shaped eight‐membered ring in II is expected to flatten on passing from the neutral molecule to its radical anion. Support for postulating such a change in geometry, analogous to that encountered with the parent cyclooctatetraene (I), is provided by INDO calculations.