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61.
62.
Commercially available cellulose (Avicel PH101) was successfully acylated under homogeneous solution conditions by the following novel procedure: 2.0 g of cellulose and 5.0 g of LiCl were introduced into a glass reactor, magnetic stirring was started, the pressure was reduced to 2 mmHg, the temperature was raised to 110°C in 30 min, and the reactor was kept under these conditions for another 30 min. N,N‐Dimethylacetamide, 60 mL, was introduced, atmospheric pressure was restored, and the temperature was raised to 150°C in 30 min. The system was kept under these conditions for 1 h, then the temperature was decreased to 40°C; in 2 h a clear cellulose solution was obtained. Acid anhydride was added, and the solution was stirred at 60°C for additional 18 h. Acetates, propionates, butyrates, and acetate/butyrate mixed ester were prepared with excellent reproducibility of the degree of substitution, from 1 to 3. The degree of polymerization of cellulose is negligibly affected by these reaction conditions. The distribution of the acetyl moiety among the three OH groups of the anhydroglucose unit follows the order C6 > C2 > C3. Features relevant to the industrial application of this novel procedure are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1355–1360, 1999 相似文献
63.
以丙酰氯、正戊酰氯、正庚酰氯为酰化试剂,在温度≤10℃下分别与氨水反应生成丙酰胺、正戊酰胺和正庚酰胺. 以吡啶作缚酸剂,将生成的酰胺与含相同碳链长的酰氯在温度≤0℃下反应,得到3种具有对称结构的含直链烷基的二烷基酰亚胺(二丙酰亚胺、二正戊酰亚胺和二正庚酰亚胺),对终产物进行了表征. 结果表明,以乙醇为良溶剂、水为不良溶剂,经多次重结晶后其最终产率分别为30%, 35%, 33%,终产物的熔点分别为153.7~154.0, 91.5~91.7, 89.0~89.5℃,二烷基酰亚胺纯度大于99%. 相似文献
64.
65.
为考察琥珀酰化改性因素对花生蛋白改性效果及结构性质的影响,采用单因素试验、响应面试验分析花生蛋白质量浓度、琥珀酸酐添加量、反应温度对改性花生蛋白酰化度与产率的影响,确定最优琥珀酰化改性条件。通过红外光谱、电子显微镜、氮溶解指数评价琥珀酰化改性花生蛋白的结构性质。结果表明:花生蛋白质量浓度、琥珀酸酐添加量是显著影响因素;最佳改性条件为花生蛋白质量浓度58.5 g/L、琥珀酸酐添加量为花生蛋白质量的19.55%、反应温度49℃,在最佳条件下改性花生蛋白酰化度与产率分别为(82.82±0.59)%和(76.89±0.74)%;引入琥珀酰基改变了花生蛋白的分子结构,使蛋白质分子由折叠趋向伸展,蛋白质聚集体尺寸减小;改性花生蛋白的溶解性得到明显改善。 相似文献
66.
酯化改性可以赋予多糖诸多新的优异性能,拓宽工业应用前景。作为生物催化剂的酶可以在有机溶剂中对多糖进行对映选择性、区域选择性的酯化,具有条件温和、步骤简单、无须基团保护、产物可生物降解等优点,符合绿色化学的理念。本文从酶催化多糖酯合成的影响因素、多糖酯的酶催化制备方法方面综述了酶催化多糖酯化反应的研究进展。 相似文献
67.
Shu BAI Mengyuan REN Lele WANG Yan SUN 《Frontiers of Chemical Engineering in China》2008,2(3):301-307
The regioselective acylation of pyridoxine catalyzed by immobilized lipase (Candida Antarctica) in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) has been investigated, and compared with that in acetonitrile (ACN). The acetylation of pyridoxine using acetic anhydride
in [BMIM]PF6 gave comparable conversion of pyridoxine to 5-monoacetyl pyridoxine with considerably higher regioselectivity (93%–95%) than
that in ACN (70%–73%). Among the tested parameters, water activity (a
w) and temperature have profound effects on the reaction performances in either [BMIM]PF6 or ACN. For the reaction in [BMIM] PF6, higher temperature (50°C–55°C) and lower a
w (<0.01) are preferable conditions to obtain better conversion and regioselectivity. Mass transfer limitation and intrinsic
kinetic from the ionic nature of ionic liquids (ILs) may account for a different rate-temperature profile and a lower velocity
at lower temperature in [BMIM]PF6-mediated reaction. Moreover, consecutive batch reactions for enzyme reuse also show that lipase exhibited a much higher thermal
stability and better reusability in [BMIM]PF6 than in ACN, which represents another advantage of ILs as an alternative to traditional solvents beyond green technology. 相似文献
68.
综述了聚氨酯用羟基化合物羟值的分析方法,并对各种方法进行了分析比较。基于醇羟基和酚羟基化合物的特殊性,分析方法有类似又有区别,实际工作中要区别对待。 相似文献
69.
70.
Keisuke Yoshida Kenji Mishiro Yoshihiro Ueda Takashi Shigeta Takumi Furuta Takeo Kawabata 《Advanced Synthesis \u0026amp; Catalysis》2012,354(17):3291-3298
A highly geometry‐selective organocatalytic acylation of tri‐ and tetra‐substituted 2‐alkylidene‐1,3‐propanediols has been developed. The highly E‐selective acylation of various tetrasubstituted 2‐alkylidene‐1,3‐propanediols was achieved in 96 to >99% selectivity for the first time by a non‐enzymatic protocol. 相似文献