Photochemical Nitration by Tetranitromethane. Part XXXV. A Possible Addition/Elimination Pathway in the Photochemical Reaction of 2,5-Di-tert-butyl-1,4-dimethoxybenzene and Tetranitromethane.
作者:Jan Olof Svensson、R. G. Hazell、A. W. Hewat、Matilde Fondo、Esther Gómez-Fórneas、Charles A. McAuliffe、Stenbjörn Styring、Cecilia Tommos、Kurt Warncke、Bryan R. Wood
DOI:10.3891/acta.chem.scand.51-0031
日期:——
The photolysis of the charge transfer complex of 2,5-di-tert-butyl-1,4-dimethoxybenzene (1) and tetranitromethane gives exclusively 4-tert-butyl-2,5-dimethoxynitrobenzene (2) in both dichloromethane and acetonitrile at room temperature. Photolysis in dichloromethane in the presence of trifluoroacetic acid (0.10-1.0 mol dm(-3)), gives 2,5-di-tert-butyl-1,4-benzoquinone (3) (6-25%), 5-tert-butyl-4-methoxy-1,2-benzoquinone (4) (9-25%) and 5-tert-butyl-4-methoxy-1,2-dihydroxybenzene (5) (13-25%) together with 2 (25-71%). Nitration of 1 with HNO3/acetic anhydride or a solution of nitrogen dioxide in dichloromethane gives 2 as the main product, together with products 3-5. It is suggested that 2 is formed in the photolysis by the decomposition of transient adducts, in which trinitromethyl and NO2 have been added across the aromatic ring. The protonation of trinitromethanide by trifluoroacetic acid eliminates the nucleophile and thus inhibits the formation of adducts, and the products are then formed mainly by coupling of nitrogen dioxide with the radical cation 1(.+) or 1.