Mobilities of solvated electrons in polar solvents from scavenging rate constants

Rate constants k/sub 8/ for the reaction of solvated electrons (e/sub 8//sup -/) with biphenyl have been determined at room temperature by fast spectrophotometric detection after pulse radiolysis. In various solvents where both k/sub 8/ and mobilities of e/sub 8//sup -/ (..mu../sub e/) are known, it has been checked that the scavenging reaction with biphenyl is diffusion controlled. Then the Smoluchowski equation may be used to determine ..mu../sub e/ from k/sub 8/ in solvents where conductivity measurements are difficult due to a high intrinsic conductance. Mobilities of e/sub 8//sup -/ have been derived in various solvents, including ethers (diethyl ether, 1,2-dimethoxyethane), amines (ethylamine, n-propylamine, ethylenediamine, hydrazine), and amides (hexamethylphosphoric triamide, HMPT). The values of ..mu../sub e/ so obtained are compared with those from the literature. For example, there is a significant discrepancy between our values and those for HMPT, n-butylamine, and tert-butylamine determined by pulse conductivity in the microsecond time range, and this discrepancy is discussed. The value of ..mu../sub e/ in ethylenediamine is larger by a factor of 4 than that of ..mu..(Na/sup -/). Finally, a rough correlation exists between ..mu../sub e/ and the energy at the absorption maximum of e/sub 8//sup -/ (E/sub max/).