过氧化氢氧化糠胺制备3-羟基吡啶

以糠胺为原料、H2O2为氧化剂制备3-羟基吡啶。考察了盐酸浓度、反应温度和反应时间对3-羟基吡啶收率的影响。最佳反应条件为:n(糠胺),n(盐酸):n(过氧化氢)=1．0:5．0:1．1,在0-5℃4 h内将过氧化氢滴加入糠胺和盐酸的混合物中,加热回流反应0．5 h,得目标产物,收率76％,质量分数99．3%。     

Two novel halogen-free,phosphorus-free,and intrinsically flame-retardant benzoxazine thermosets containing electron-withdrawing bridge groups

Two novel furfurylamine type benzoxazine prepolymers are firstly synthesized from 4,4′-bishydroxydeoxybenzoin (BHDB) and 4,4′-dihydroxybenzophenone (DHBP). Both BHDB- and DHBP-based polybenzoxazines present accelerated curing behaviors, high glass transition temperatures, and very low heat release capacity values, resulting from the introduction of electron-withdrawing groups and furan rings. It is especially noteworthy that the flame retardancy of DHBP-based polybenzoxazine is classified as UL-94 V-1 grade, whereas that of BHDB-based polybenzoxazine is evaluated to be UL-94 V-2 grade. Hence, DHBP is considered as an alternative to BHDB for benzoxazine preparation because of its similar chemical structure, competitive price, high efficiency preparation, and outstanding flame resistance. Therefore, this work not only provides an economical and effective strategy for the preparation of halogen-free, phosphorus-free, and intrinsically flame-retardant benzoxazine resins but also provides important insight into the effects of electron-withdrawing bridge groups on the curing behavior and thermal and flame-retardant properties of benzoxazine resins.