摘要
2,2,6,6-四甲基哌啶氧化物自由基(TEMPO)-NaClO-NaBr是一种新的具有很高选择性的氧化体系。文章研究了该体系在pH 9.30和体系温度为0℃时对瓜尔胶的氧化机理。用IR和13C-NMR表征了瓜尔胶及羟丙基瓜尔胶在氧化后的结构变化,证实了经氧化后(羟丙基)瓜尔胶结构中C6上伯醇可被选择性转化为羧基;另外在本实验条件下,随着瓜尔胶羟丙基取代度的增加,其氧化程度也增加。
2,2,6,6-Tetramethyl-1-piperidinyloxy radical （TEMPO）-NaClO-NaBr mediated oxidation of guar was studied at pH 9. 30 and at temperature of 0 ℃ with NaOCl as the primary oxidant. Two phases were observed from typical kinetic plot of TEMPO-mediated oxidation of guar gum as monitored by the consumption of NaOH. From the IR spectra, the absorption bands of the C=O was observed in the 1615 cm^-1 while it shifted to the 1739 cm^-1 after acidifying the sampies. It indicates that the absorption bands of oxidized guar gum is -COOH group. From ^13C- NMR spectra the fact that the carboxylate resonate could be found at near 175 indicates that the hydroxyl of C6 is oxidized to -COOH. But no resonance in the 198-210 region was observed, indicating no ketone group formation during the oxidation. Furthermore, the degree of oxidation of guar gum increased with the increasing substitution degree of hydroxypropyl group in guar gum under this experiment condition.
出处
《高分子材料科学与工程》
EI
CAS
CSCD
北大核心
2007年第4期211-214,218,共5页
Polymer Materials Science & Engineering
基金
科技部中法先进研究计划国际合作项目(PRA-MX-0304)
