Hydroxyl radical induced oxidation of acetaldehyde dimethyl acetal in oxygenated aqueous solution. Rapid O sub 2 sup sm bullet minus release from the CH sub 3 C(OCH sub 3 ) sub 2 O sub 2 sup sm bullet radical

Journal Article · Wed Jan 03 04:00:00 EST 1990 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00157a060· OSTI ID:6592163

Schuchmann, M N; Schuchmann, H P; von Sonntag, C ^[1]

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1. Max-Planck-Institut fuer Strahlenchemie, Ruhr (Germany, F.R.)

The oxidative degradation of acetaldehyde dimethyl acetal in dilute aqueous solutions has been studied kinetically by pulse radiolysis and with respect to product formation by both {gamma}-radiolysis and pulse radiolysis. In N{sub 2}O-saturated solutions, H abstraction from the substrate by the OH radical produces the radicals CH{sub 3}CH(OCH{sub 3})OCH{sub 2}{sup {sm bullet}} (1), CH{sub 2}C{sup {sm bullet}}(OCH{sub 3}){sub 2} (2), and {sup {sm bullet}}CH{sub 2}CH(OCH{sub 3}){sub 2} (3). Radicals 1 and 2 have reducing properties and react rapidly with tetranitromethane, yielding nitroform anion. Radical 3 is probably inert toward this compound on the pulse radiolysis time scale. While 1 forms an adduct with an observable lifetime (k(dec) = 4.4 {times} 10{sup 4} s{sup {minus}1}), 2 gives rise to the immediate formation of nitroform anion. It has been estimated that the radicals are formed with G values of G(1) = 0.34, G(2) = 0.21, and G(3) {le} 0.02 {mu}mol J{sup {minus}1}. In N{sub 2}O/O{sub 2} (4:1, v/v) saturated solutions, the products are (G ({mu}mol J{sup {minus}1}) in parentheses) formaldehyde (0.16), methanol ({approx} 0.3), acetaldehyde (0.15), methyl acetate (0.21), formic acid (0.16), hydrogen peroxide (0.14), and organic hydroperoxide (0.19). As shown by pulse radiolysis, oxygen reacts with radicals 1-3 with a rate constant of k {ge} 2 {times} 10{sup 9} dm{sup 3} mol{sup {minus}1} s{sup {minus}1}, yielding (mainly) the peroxyl radicals CH{sub 3}CH(OCH{sub 3})OCH{sub 2}O{sub 2}{sup {sm bullet}} (4) and CH{sub 3}C(OCH{sub 3}){sub 2}O{sub 2}{sup {sm bullet}} (5). Peroxyl radical 5 cleaves off O{sub 2}{sup {sm bullet}{minus}} in a fast reaction (k = 6.5 {times} 10{sup 4} s{sup {minus}1}), which subsequently leads to the formation of methyl acetate and methanol.

• OSTI ID: 6592163
• Journal Information: Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 112:1; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400600* -- Radiation Chemistry
ACETAL
ACETALS
ALCOHOLS
AQUEOUS SOLUTIONS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DATA ANALYSIS
DECOMPOSITION
DISPERSIONS
ETHERS
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
HYDROXY COMPOUNDS
HYDROXYL RADICALS
INFORMATION
MEASURING INSTRUMENTS
MEASURING METHODS
METHANOL
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
PEROXIDES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
SOLUTIONS