TEMPO-mediated oxidation on galactomannan: Gal/Man ratio and chain flexibility dependence
| Autor: | Neoli Lucyszyn, Maria Rita Sierakowski, Caroline Novak Sakakibara, Rilton Alves de Freitas |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
chemistry.chemical_classification
Guar gum Polymers and Plastics Ion exchange Carboxylic acid Organic Chemistry Size-exclusion chromatography 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Catalysis Galactomannan chemistry.chemical_compound Residue (chemistry) chemistry Materials Chemistry Organic chemistry Locust bean gum 0210 nano-technology Nuclear chemistry |
| Zdroj: | Carbohydrate polymers. 153 |
| ISSN: | 1879-1344 |
| Popis: | Guar (GG) and locust bean (LBG) galactomannans (GMs) oxidation at C-6 was performed with catalyst TEMPO, in which the reaction progress was monitored by consume of NaOH solution. The products were characterized by spectroscopic analysis, infrared, and (1)H-nuclear magnetic resonance, confirming the presence of aldehydes groups as intermediate of reaction to carboxylic acid. From high performance anion exchange chromatography with pulsed amperometric detection Man/Gal molar ratio was determined and demonstrated a preference to oxidize Man during the reaction on both GMs, following a first order kinetics of oxidation. The comparative macromolecular behavior of native and oxidized GMs was obtained through the analysis by high performance size exclusion chromatography, and the persistence length (Lp) was 6nm and 4nm to native LBG and GG, respectively. A more accessible OH-6 at mannose residue in LBG could be related with a two times faster reaction than GG. The selective oxidation with catalyst TEMPO proved to be efficient to increase the flexibility of the GMs during oxidation. Short reaction time and β-elimination process were mainly observed to LBG, probably due to a more favorable oxidation access to the polysaccharide main chain. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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