Radiation-induced Rearrangement of Ethylene Glycol in Aqueous Solution

Abstract

Under y-irradiation, aqueous solutions of ethylene glycol containing hydrogen peroxide form acetaldehyde as a major product via a free-radical chain rearrangement. The yield of acetaldehyde is essentially unchanged when hydrogen peroxide is replaced by N 2 0 or HC104. A mechanism is proposed in which the glycol radical, ~H O H C H~O H , rearranges to the acetaldehyde precursor, c H 2 C H 0 , followed by the hydrogen atom transfer reaction; thus propagating a chain r e a~t i o n .~The rearrangement is also induced by the photo-dissociation of H 2 0 2 in aqueous solutions of ethylene glycol.Sous une y-irradiation, des solutions aqueuses d'ethylene glycol contenant du peroxyde d'hydrogene produisent de I'acCtaldChyde comme produit principal par une transposition radicalaire en chaine. Le rendement en adtaldChyde n'est pas modifiC lorsque le peroxyde d'hydrogtne est remplacC par N 2 0 ou HCIO.+. Un m h n i s m e est propose ou le radical glycol, cH0HCH2OH, se transpose en un prCcurseur, c H 2 C H 0 , de I'acetaldthyde suivi par une reaction de transfert d'atome d'hydrogene; il en rCsulte une rCaction de propagation en chaine.2 Dans des solutions aqueuses d'Cthylene glycol, la transposition peut Cgalement Ctre induite par la photo-dissociation de H202.

Aqueous chemistry and its role in secondary organic aerosol (SOA) formation

“…Radical-radical reaction rates are considered to be diffusion controlled (Guzman et al, 2006) with a suggested value of ∼2×10 9 M −1 s −1 for the combination of two pyruvic radical species, [H 3 C-C*(OH)-C(O)OH]. This is consistent with the value of ∼1×10 9 M −1 s −1 for the combination of two acetaldehyde radical species, [H 2 C*-CHO] (Burchill et al, 1971).…”

“…(A) Formation of 2,3-dimethyltartaric acid via radicalradical reactions (Guzmann et al, 2006). (B) Dehydration of the glyoxal radical (Burchill and Perron, 1971). (C) Formation of tartaric acid (m/z − 149) via radical-radical reactions followed by dehydration.…”

Electron Spin Resonance Studies in Aqueous Solution: Fragmentation of Radical Intermediates Derived from β-Amino Alcohols

“…It has been suggested that the rate of the uncatalyzed elimination (eq. 2), was too slow at high steady-state radical concentrations to compete with bimolecular termination (7). Indeed, continuous y irradiation of neutral aqueous solutions of 1,2-ethanediol containing added H 2 0 2 (7) or N,O (8) revealed a chain reaction that produced acetaldehyde.…”

Fundamental Heterogeneous Reaction Chemistry Related to Secondary Organic Aerosols (SOA) in the Atmosphere

“…A favorable condition for the radical-radical reactions can be achieved first if the radical-radical reaction rate constants are large enough compared with the large reaction rate constant with O 2 , ∼10 9 M −1 s −1 (Buxton et al, 1997). The rate constants of radicalradical reactions in the aqueous phase are, in general, as large as these which are diffusion controlled with suggested values of ∼10 9 M −1 s −1 (Burchill and Perron, 1971; Guzmán et al, 2006). Second, since the concentration of the dissolved O 2 in cloud water is ∼0.3 mM , the concentration of the precursor, glyoxal or methylglyoxal should be high enough to provide a high concentration of radicals.…”