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Abiotic C-C bond formation under environmental conditions: kinetics of the aldol condensation of acetaldehyde in water catalyzed by carbonate ions (CO32-)
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
2010 (English)In: International Journal of Chemical Kinetics, ISSN 0538-8066, E-ISSN 1097-4601, Vol. 42, no 11, 676-686 p.Article in journal (Refereed) Published
Abstract [en]

The role of CC bond-forming reactions such as aldol condensation in the degradation of organic matter in natural environments is receiving a renewed interest because naturally occurring ions, ammonium ions, NH+4, and carbonate ions, CO32−, have recently been reported to catalyze these reactions. While the catalysis of aldol condensation by OH has been widely studied, the catalytic properties of carbonate ions, CO32−, have been little studied, especially under environmental conditions. This work presents a study of the catalysis of the aldol condensation of acetaldehyde in aqueous solutions of sodium carbonate (0.1–50 mM) at T = 295 ± 2 K. By monitoring the absorbance of the main product, crotonaldehyde, instead of that of acetaldehyde, interferences from other reaction products and from side reactions, in particular a known Cannizzaro reaction, were avoided. The rate constant was found to be first order in acetaldehyde in the presence of both CO32− and OH, suggesting that previous studies reporting a second order for this base-catalyzed reaction were flawed. Comparisons between the rate constants in carbonate solutions and in sodium hydroxide solutions ([NaOH] = 0.3–50 mM) showed that, among the three bases present in carbonate solutions, CO32−, HCO3, and OH, OH was the main catalyst for pH ≤ 11. CO32− became the main catalyst at higher pH, whereas the catalytic contribution of HCO3 was negligible over the range of conditions studied (pH 10.3–11.3). Carbonate-catalyzed condensation reactions could contribute significantly to the degradation of organic matter in hyperalkaline natural environments (pH ≥ 11) and be at the origin of the macromolecular matter found in these environments.

Place, publisher, year, edition, pages
2010. Vol. 42, no 11, 676-686 p.
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-44826DOI: 10.1002/kin.20518OAI: diva2:362655
Available from: 2010-11-09 Created: 2010-11-09 Last updated: 2010-12-10Bibliographically approved

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Noziere, Barbara
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