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I. D. Sorokin, O. L. Melnikova, V. I. Pergushov, D. A. Tyurin, V. I. Feldman, M. Ya. Melnikov
Photoconversions of methyloxiranes radical cations in in
freonic matrices at 77 K
Abstract
It has been shown that upon x-ray
irradiation of various methyloxiranes in freonic matrices at 77 K radical
cations may be stabilized both in the open form and in the cyclic form with an
elongated C–C bond. It has been established that reversible photoinduced
transformations of 2,3-dimethyloxirane and methyloxirane are associated with a
transition between the open and cyclic forms of the radical cations that
proceeds with high quantum yields (0.02 – 0.39, depending on the oxirane or the
matrix). In the case of trimethyloxirane radical cations the influence of light
on the trans-isomer of the open
forms promotes it photoinduced transformation into a C-centered radical with
low quantum efficiency (~4×10-3). Radical cations
of tetramethyloxirane that are stabilized in the open form are resistant to the
action of light. Possible causes of the observed effects are discussed. Upon
the x-ray irradiation of 2,2-dimethyloxirane in freonic matrices at 77 K, a
cyclic form of the radical cations is formed (supposedly, as part of a complex
with matrix molecules) which transforms into a distonic C-centered radical
cation upon the action of light with a quantum yield of ~10-3.
Copyright (C) Chemistry Dept., Moscow State University, 2002
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