Proton Transfer between Styrene Molecular Anion and Ethanol in Rigid Organic Matrices

The proton transfer from ethanol to styrene molecular anion was studied by examining the yield of the anion and α-methylbenzyl radical generated in γ-irradiated 2-methyltetrahydrofuran–ethanol mixed matrix at 77 K by means of optical absorption measurements. The radical yield was found to increase in proportion to the ethanol fraction at the expense of the anion yield. The maximum radical yield, 2.2, was identical with the yield of scavengeable electron in ethanol matrix where no anion was observed. Upon photobleaching the anion was transformed into the radical in the matrix. The transformation efficiency was constant, ca. 0.6, for the ethanol fraction 0.3–0.9. It is concluded that the radical arises from the anion through the proton transfer from ethanol to the β-carbon of vinyl group of the styrene anion. The proton transfer occurs readily only when a specific solvent site around the anion is populated by ethanol molecules. Otherwise, the proton transfer does not occur at all because of the restricted translational motion in the rigid matrix.