38241-07-5Relevant academic research and scientific papers
Neophyl-like Rearrangement of Alkoxy Radicals: Direct Detection of a Bridged Intermediate by Time-Resolved Absorption Spectroscopy
Falvey, Daniel E.,Khambatta, Binaifer S.,Schuster, Gary B.
, p. 1056 - 1059 (1990)
The neophyl-like rearrangment of alkoxy radicals was examinde by means of picosecond time scale absorption spectroscopy.The triphenylmethoxy radical (Ph3CO.) rearranges to form the α-phenoxydiphenylmethyl radical (Ph2COPh.) with a rate constant greater than 5 x 1010 s-.The rearrangment of 1,1-diphenylethoxy radical (PhCH3CO.) was also examined.In acetonitrile solution, an intermediate is formed in less than 17 ps and then decays with a lifetime of 312 ns.It is proposed that this intermediate is a brigded spirooctadiene-type radical.
The effect of ring substitution on the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals. A product and time-resolved kinetic study
Aureliano Antunes, Carla S.,Bietti, Massimo,Ercolani, Gianfranco,Lanzalunga, Osvaldo,Salamone, Michela
, p. 3884 - 3891 (2007/10/03)
A product and time-resolved kinetic study of the effect of ring substitution on the reactivity of 1,1-diarylalkoxyl radicals has been carried out. The radicals undergo an O-neophyl shift to give the isomeric 1-aryl-1-aryloxyalkyl radicals from which the corresponding aromatic ketones are formed. The rearrangement rate constants are influenced by ring substitution, increasing in the presence of electron-withdrawing substituents and decreasing in the presence of electron-donating ones. From the results of product and kinetic studies, the following migratory aptitudes have been obtained: 4-trifluoromethylphenyl > phenyl ? 4-methylphenyl > 4-methoxyphenyl. Excellent Hammett-type correlations between the σ+ substituent constants and both the visible absorption band maxima and the rearrangement rate constants have been obtained. The experimental results indicate that the rearrangement is governed by electronic effects in the starting 1,1-diarylalkoxyl radicals, whereas the stability of the rearranged carbon-centered radical plays a minor role, in line with a reactant-like transition state, strongly supporting the hypothesis that the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals proceeds through a concerted mechanism.
