Direct Evidence for Base-Mediated Decomposition of Alkyl Hydroperoxides (ROOH) in the Gas Phase
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.Journal of the American Chemical Society (Impact Factor: 12.11). 05/2002; 124(13):3196-7. DOI: 10.1021/ja017658c
The reaction of F(-) with CH(3)OOH has been studied in the gas phase using a tandem flowing afterglow-selected ion flow tube apparatus. The reaction is rapid (k = 1.23 x 10(-9) cm(3) s(-1), 49% efficiency), and formation of HO(-) + CH(2)O + HF is the major reaction channel observed (85%). Isotopic labeling, reactions of F(-) with larger alkyl hydroperoxides, and computational studies demonstrate that the major product ion, HO(-), is formed via a concerted elimination mechanism that appears to be general to all alkyl hydroperoxides possessing an alpha-hydrogen. This mechanism represents a base-mediated decomposition of alkyl hydroperoxides in the gas phase that may have important implications for solution and biochemical reactions. The reverse reaction, CH(3)OO(-) + HF is also efficient (k = 2.43 x 10(-9) cm(3) s(-1)). The major product ensemble HO(-) + CH(2)O + HF (81%) is identical to that of the forward reaction, and represents a novel neutral-catalyzed decomposition of the anion.
Full-text previewDOI: · Available from: colorado.edu
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
[Show abstract] [Hide abstract]
- "Lipid derived hydroperoxides formed produced by LOX can be converted to a wide variety of functional oleochemicals precursors by three main conversion routes: acid-catalyzed decomposition, free-radical decomposition and base-catalyzed decomposition as schematically illustrated in Figure 5 (Blanksby et al., 2002; Frankel, 2005; Frankel & Gardner, 1989; Gardner, 1989; Gardner et al., 1984). LOX-catalyzed production of hydroperoxides can be regarded more sustainable process than chemical technologies using ozone oxidation (Nishikawa et al., 1995; Reynolds et al., 2006). "
ABSTRACT: Abstract Lipoxygenases (LOXs) are iron- or manganese-containing oxidative enzymes found in plants, animals, bacteria and fungi. LOXs catalyze the oxidation of polyunsaturated fatty acids to the corresponding highly reactive hydroperoxides. Production of hydroperoxides by LOX can be exploited in different applications such as in bleaching of colored components, modification of lipids originating from different raw materials, production of lipid derived chemicals and production of aroma compounds. Most application research has been carried out using soybean LOX, but currently the use of microbial LOXs has also been reported. Development of LOX composition with high activity by heterologous expression in suitable production hosts would enable full exploitation of the potential of LOX derived reactions in different applications. Here, we review the biological role of LOXs, their heterologous production, as well as potential use in different applications. LOXs may fulfill an important role in the design of processes that are far more environmental friendly than currently used chemical reactions. Difficulties in screening for the optimal enzymes and producing LOX enzymes in sufficient amounts prevent large-scale application so far. With this review, we summarize current knowledge of LOX enzymes and the way in which they can be produced and applied.