Pulse Radiolysis Studies II. Transient Spectra and Rate Processes in Irradiated Ethanol and Aqueous Ethanol Solution

Authors: I. A. Taub, L. M. Dorfman

The radiation chemistry of deaerated aqueous ethanol and deaerated liquid ethanol has been studied by the pulse radiolysis technique. The same transient absorption spectrum, showing a broad weak absorption at about 290 mU and stronger narrow peaks at 266, 257 and 247 mU, has been observed in both systems. It is concluded that the spectrum is that of the alpha-ethanol radical, CH3CHOH. The molar extinction coefficient in water is estimated to be e2967 = 230 ± 55 Af-1 cm.-1. From the rate curves for the disappearance of the transient, determined by fast photoelectric spectrophotometry, the abso-lute rate constant for the bimolecular reaction of two α-ethanol radicals in water, at 23°, is found to be: 2kb = (1.1 ± 0.3) X 109 A7-1 sec.-1. The bimolecular rate constant in ethanol, at 23°, is found to be: 2kb = (3.3 ± 0.2) X 106 e’2967 A/-1 sec.-1, where e’2967 is the molar extinction coefficient at 2967 A of the α-ethanol radical in ethanol. The radiation chemical yields of 2,3-butanediol and acetaldehyde have been determined in both systems, along with the hydrogen yields in heavy water solutions.

https://doi.org/10.1021/ja00880a016