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 00:00:00 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), Vol. 112:1; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

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