The Bisketene Radical Cation and Its Formation by Oxidative Ring-Opening of Cyclobutenedione

Parent cyclobutenedione 1 was photolyzed and ionized in an Ar matrix at 10K. The bisketene 2 that results in both cases (in the form of its radical cation after ionization) was characterized by its IR spectrum and by high-level quantum chemical calculations. Experiment and theory show that the neutr...

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Bibliographic Details
Published in:Journal of organic chemistry 2013-04, Vol.78 (7), p.2908-2913
Main Authors: Piech, Krzysztof, Bally, Thomas, Allen, Annette D, Tidwell, Thomas T
Format: Article
Language:English
Subjects:
Cations - chemistry
Cyclobutanes - chemistry
Free Radicals - chemistry
Ketones - chemistry
Molecular Structure
Oxidation-Reduction
Photolysis
Quantum Theory
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Summary:Parent cyclobutenedione 1 was photolyzed and ionized in an Ar matrix at 10K. The bisketene 2 that results in both cases (in the form of its radical cation after ionization) was characterized by its IR spectrum and by high-level quantum chemical calculations. Experiment and theory show that the neutral bisketene has only a single conformation where the two ketene moieties are nearly perpendicular, whereas the radical cation is present in two stable planar conformations. The mechanism of the ring-opening reaction, both in the neutral and in the radical cation, is discussed on the basis of calculations. In the latter case it is a nonsynchronous process that involves an avoided crossing of states.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo3025708