5651-05-8Relevant academic research and scientific papers
Importance of Unimolecular HO2 Elimination in the Heterogeneous OH Reaction of Highly Oxygenated Tartaric Acid Aerosol
Cheng, Chiu Tung,Chan, Man Nin,Wilson, Kevin R.
, p. 5887 - 5896 (2016/08/06)
Oxygenated organic molecules are abundant in atmospheric aerosols and are transformed by oxidation reactions near the aerosol surface by gas-phase oxidants such as hydroxyl (OH) radicals. To gain better insights into how the structure of an organic molecule, particularly in the presence of hydroxyl groups, controls the heterogeneous reaction mechanisms of oxygenated organic compounds, this study investigates the OH-radical initiated oxidation of aqueous tartaric acid (C4H6O6) droplets using an aerosol flow tube reactor. The molecular composition of the aerosols before and after reaction is characterized by a soft atmospheric pressure ionization source (Direct Analysis in Real Time) coupled with a high-resolution mass spectrometer. The aerosol mass spectra reveal that four major reaction products are formed: a single C4 functionalization product (C4H4O6) and three C3 fragmentation products (C3H4O4, C3H2O4, and C3H2O5). The C4 functionalization product does not appear to originate from peroxy radical self-reactions but instead forms via an α-hydroxylperoxy radical produced by a hydrogen atom abstraction by OH at the tertiary carbon site. The proximity of a hydroxyl group to peroxy group enhances the unimolecular HO2 elimination from the α-hydroxylperoxy intermediate. This alcohol-to-ketone conversion yields 2-hydroxy-3-oxosuccinic acid (C4H4O6), the major reaction product. While in general, C-C bond scission reactions are expected to dominate the chemistry of organic compounds with high average carbon oxidation states (OSC), our results show that molecular structure can play a larger role in the heterogeneous transformation of tartaric acid (OSC = 1.5). These results are also compared with two structurally related dicarboxylic acids (succinic acid and 2,3-dimethylsuccinic acid) to elucidate how the identity and location of functional groups (methyl and hydroxyl groups) alter heterogeneous reaction mechanisms.
The oxidation of fructose on Pt/C catalysts. The formation of D-threo- hexo-2,5-diulose and the effect of additives
Heinen, Annemieke W.,Peters, Joop A.,Van Bekkum, Herman
, p. 155 - 164 (2007/10/03)
This paper describes a study on the oxidation of D-fructose with molecular oxygen on Pt/C catalysts. Two major products are formed: 2-keto-D- gluconic acid and D-threo-hexo-2,5-diulose ('5-ketofructose'). Deactivation of the catalyst was observed, caused both by over-oxidation of the active surface and inhibition of the reaction by 2-ketogluconic acid. Although promotion of the catalyst with bismuth did not prevent deactivation, it improved the selectivity to 2-ketogluconic acid, probably due to coordination of fructose to the promoter. Other promoting metals (tin, lead and antimony) and additives like borate and hexamethylenetetramine were less successful.
