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Reactivity and reaction patterns of alkyl alkoxybenzene radical cations. Mechanistic pathways of the reactions between 2,5‐DI‐ tert ‐Butyl‐1, 4‐Dimethoxybenzene and perfluorodiacyl peroxides
Author(s) -
Jiang XiKui,
Zhao ChengXue,
Gong YueFa
Publication year - 1991
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610040102
Subject(s) - chemistry , reactivity (psychology) , carbocation , nucleophile , medicinal chemistry , solvent , yield (engineering) , photochemistry , electron paramagnetic resonance , acetic acid , radical ion , fragmentation (computing) , electron transfer , methanol , radical , alkyl , organic chemistry , ion , catalysis , medicine , materials science , alternative medicine , physics , pathology , nuclear magnetic resonance , computer science , metallurgy , operating system
In the reactions of 2,5‐di‐ tert ‐butyl‐1,4‐dimethoxybezene (1) with different oxidants, the radical cation 1 +. is always detectable by EPR. However, the observed reactivity of 1 +. depends greatly on the oxidation systems employed. In S 2 O 8 2− Cu 2+ HOAc and Ce 4+ HOAc systems (HOAc = acetic acid), 1 +. appears to have long lifetimes and does not undergo fragmentation spontaneously. In contrast, in (R F CO 2 ) 2 CF 2 CICFCI 2 (F113) systems, the readily formed 1 +. is short‐lived, and large amounts of de‐ tert ‐butylation products have been isolated. Experimental results imply that the CC bond cleavage involved in de‐ tert ‐butylation could be a consequence of an attack by perfluoroacyloxy radical on 1 +. in their original solvent cage. The fact that addition of methanol to the reaction mixture leads to the formation of a large amount of t BuOCH 3 (46%) and other evidence suggest that the tert ‐butyl group leaves as a carbocation. On the basis of these results, we conclude that the reactions of 1 with (R F CO 2 ) 2 are initiated by electron transfer and followed by a fast coupling of various radical species, namely, 1 +. with R F CO 2 or with R F in the solvent cage, to form σ‐complexes which collapse or react with nucleophiles to yield the final products.