BioPol, Chemistry Department, Federal University of Paraná, Curitiba, Paraná, 81531-980, Brazil; Tulane Center for Polymer Reaction Monitoring and Characterization (PolyRMC), Tulane University, New Orleans, LA, 70118, USA.
BioPol, Chemistry Department, Federal University of Paraná, Curitiba, Paraná, 81531-980, Brazil.
Carbohydr Polym. 2017 Aug 15;170:140-147. doi: 10.1016/j.carbpol.2017.04.064. Epub 2017 Apr 26.
Polysaccharide TEMPO-oxidation was monitored using automatic continuous online monitoring of polymerization reactions (ACOMP). The products of oxidation, obtained at different pHs (9, 7 and 5) and different concentrations of catalyst TEMPO, were evaluated by Automatic Continuous Mixing (ACM) and Size Exclusion Chromatography (SEC). The degree of oxidation was higher at pH 9 and polysaccharide degradation was observed under different pH conditions, but was much higher without catalyst TEMPO. The rate constant (k) was dependent on reaction pH and TEMPO concentration. The amount of -COOH per g of polysaccharide, at pH 9, in the presence and absence of TEMPO was different, 0.215 and 0.395mmolg, respectively. This suggested a secondary and non-selective polysaccharide oxidation occurring at a lower rate in the absence of catalyst. TEMPO protects the polysaccharide from degradation caused by secondary oxidant species, acting as a catalyst and "sacrificial molecule" at higher concentrations.
采用自动连续聚合反应监测（ACOMP）对多糖 TEMPO 氧化进行监测。在不同 pH 值（9、7 和 5）和不同 TEMPO 催化剂浓度下氧化得到的产物，通过自动连续混合（ACM）和尺寸排阻色谱（SEC）进行评估。在 pH 9 时氧化程度更高，并且在不同 pH 条件下观察到多糖降解，但在没有 TEMPO 催化剂的情况下降解程度更高。速率常数（k）取决于反应 pH 值和 TEMPO 浓度。在 pH 9 时，存在和不存在 TEMPO 时每克多糖的-COOH 量分别为 0.215 和 0.395mmol/g。这表明在没有催化剂的情况下，会发生次要的、非选择性的多糖氧化，其反应速率较低。TEMPO 可以保护多糖免受次级氧化剂引起的降解，在较高浓度下，TEMPO 作为催化剂和“牺牲分子”发挥作用。
