Revised structure of a purported 1,2-dioxin: a combined experimental and theoretical study.
3,6-Bis(p-tolyl)-1,2-dioxin (1g) was suggested by Shine and Zhao as a product in an electron-transfer (ET) photochemical reaction. This photoproduct is instead shown to be (E)-1,4-di-p-tolylbut-2-ene-1,4-dione ((E)-4a). Ab initio and DFT calculations indicate that ring-closed 1,2-dioxin is thermodynamically far less stable than open-chain but-2-ene-1,3-dione. These calculations indicate that (E)-4a is formed via the cation radical of 1g, which sequentially isomerizes to a novel sigma-radical with an O,O 3e bond [(Z)-4a](+)(*), undergoes ET to give (Z)-4a, and then photoisomerizes to (E)-4a.
Department of Chemistry, State University of New York at Albany, 12222, USA. eb801@albany.edu
Eric
E
Block
Zhixing
Z
Shan
Richard S
RS
Glass
Jürgen
J
Fabian
D003500:Cyclization; D004147:Dioxins / Q000737:chemistry*; D004563:Electrochemistry; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism
D004147:Dioxins