A pulse radiolysis study of solvated electrons in dilute solutions of polar liquids in nonpolar solvents

Abstract

Measurements of the conductivities following electron pulse irradiation of dilute solutions of ethanol, n-propanol, tert-butanol, or dimethyl sulphoxide in n-hexane, cyclohexane, or i-octane are quantitatively consistent with the existence of equilibria between electrons in the hydrocarbon and electrons solvated by dimers of the polar molecules. With dimethylformamide solutions in alkanes the equilibrium could be with the monomeric anion of the solute but this assignment is not unequivocal. Absorption spectra of es− in n-hexane solutions of ethanol and of tert-butanol have been obtained.

Electron Trapping by Polar Molecules in Alkane Liquids: Cluster Chemistry in Dilute Solution

“…23 The resulting e S n solv − { } : species should be at least a tetramer. 19 The same applies to solvated electron observed in water-saturated alkanes, 20,23 though the corresponding spectrum more closely resembles that of the excess electron in dense water vapor 31 and supercritical water 32 than hydrated electron in liquid water. 2 For χ >0.1, there is no evolution of the TA spectra after the 30 ps electron pulse.…”

“…44 Our conductivity measurements suggest that for dilute solutions of acetonitrile or alcohol in alkanes the free electron yield indeed does not change due to the occurrence of reactions (2) and (3) (see sections 4.2.1 and 4.2.2, respectively). However, in the dose regime typical of pulse radiolysis -TA studies [19][20][21][22][23][24] (as opposed to pulse radiolysis -d.c. conductivity studies), [21][22][23]25 this is not the case. Since for alcohols, electron attachment reaction (2) occurs with a rate constant > 10 12 M -1 s -1 , 25 electron trapping in 0.1 M ethanol occurs well within the geminate stage.…”

“…Hereafter, electron "trapping" or "attachment" refers to the formation of a e S n solv Mozumder's paper 18 outlining this scenario stimulated a brief flurry of experimental activity. [19][20][21][22][23][24][25][26][27] It was expected that small electron clusters, as opposed to solvated electrons in neat liquids, would be simple to study and to model. (Similar expectations were later nurtured for gas phase cluster anions).…”

“…(Similar expectations were later nurtured for gas phase cluster anions). Electron localization in dilute solutions of water and alcohols in liquid [19][20][21][22][23][24][25][26] and vitreous e.g., 27 alkanes was studied using pulse radiolysis -transient absorbance (TA) spectroscopy, 19,20,23,24,27 time-resolved conductivity, [21][22][23][24][25] and optically detected magnetic resonance (ODMR). 26 The results obtained in these studies hinted at a complex picture of electron dynamics and the interest in mixed solvents quickly waned.…”

“…19 In fact, this reaction has not been observed even on a longer time scale. [20][21][22][23][24][25] The only observation of a cluster-growth reaction similar to reaction (5) is by Ahmad et al 22 who observed, albeit indirectly, slow (ca. 7x10 9 M -1 s -1 ) complexation of methanol with the tentative water tetramer in isooctane.…”