According
to picosecond radiolysis data, primary radical cations
in irradiated carbonates are very rapidly deprotonated. At the same
time, analysis of the radiation-induced fluorescence from carbonate
solutions indicates the formation of solvent-related radical cationic
species with a relatively long lifetime. We use quantum chemical methods
to develop a model of carbonate ionization that reconciles these conflicting
data. Using ethylene carbonate as an example and assuming that its
molecules exist in solution as a collection of dimeric associates,
we show that both processes are the result of the loss of an electron
from such dimers. This demonstrates that the generally accepted conceptualization
of a primary ionization event, based on the idea of the formation
of a radical cation of an individual molecule of an irradiated substance,
requires revision in the case of polar aprotic liquids that tend to
form molecular associates.
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