Oxoammonium cation (TEMPO⁺) is a powerful oxidant, generated from nitroxyl radicals (TEMPO). The compound has attracted vast attention as a promising selective oxidant in biology and materials fields. Although TEMPO is regarded as a “green” chemical, its use with halogenated co-oxidants has raised serious environmental concerns. In this study, a halogen-free process has been developed by using ozone as an effective, low-cost, and environmentally-friendly alternative in the generation of TEMPO⁺. An iodine titration combined with UV-Vis spectroscopy is employed to quantitatively monitor the reaction at a fast speed. The results showed that the conversion of TEMPO reached 70% when the ozone feed content and the reaction time were optimized at 25.60 mM and 45 min, at 4-5 °C, in H₂SO₄ solution. The TEMPO conversion rate is dependent on the reaction time. A fast reaction rate was observed in the first fifteen-min period and became slower in the subsequent period, depending on the ozone feed contents. The difference in concentrations of the TEMPO and the TEMPO⁺ decreases in the presence of high ozone feed contents, implying the high selectivity of ozone towards TEMPO oxidation to form TEMPO⁺ over the disproportionation in acid solutions. The developed “green and mild” process has a high potential for selective oxidation of primary alcohols to other high-value products. The optimized conditions were employed to prepare TEMPO⁺ for use in the oxidation of quaternized chitosan (QC). Chemical structures of the resulting chitosan polyampholyte (CPA) products were characterized, and the degree of oxidation (DO) was determined. CPA with an OD value as high as 100% was obtained with 1.867 mmol of TEMPO⁺ per gram of QC.

氧铵阳离子 (TEMPO ⁺ ) 是一种强氧化剂，由硝酰基自由基 (TEMPO) 产生。该化合物作为生物和材料领域有前途的选择性氧化剂引起了广泛关注。尽管 TEMPO 被认为是一种“绿色”化学品，但它与卤化助氧化剂的使用引起了严重的环境问题。在这项研究中，通过使用臭氧作为 TEMPO ⁺生成的有效、低成本和环保替代品，开发了一种无卤工艺。碘滴定结合紫外-可见光谱用于快速定量监测反应。结果表明，当臭氧进料含量和反应时间优化为 25.60 mM 和 45 min，在 4-5 °C，在 H 中时，TEMPO 的转化率达到 70%₂ SO ₄溶液。TEMPO 转化率取决于反应时间。在第一个 15 分钟期间观察到快速反应速率并且在随后的时段中变得更慢，这取决于臭氧进料含量。在高臭氧进料含量的存在下，TEMPO 和 TEMPO ^{+ 的}浓度差异减小，这意味着臭氧对 TEMPO 氧化形成 TEMPO ⁺的高选择性超过酸溶液中的歧化。开发的“绿色和温和”工艺具有将伯醇选择性氧化成其他高价值产品的巨大潜力。采用优化条件制备 TEMPO ⁺用于季铵化壳聚糖 (QC) 的氧化。表征了所得壳聚糖聚两性电解质 (CPA) 产品的化学结构，并确定了氧化度 (DO)。每克 QC使用 1.867 mmol TEMPO ⁺获得 OD 值高达 100% 的 CPA 。