【作者】 单海霞；

【导师】 曹玉华； 李在均；

【作者基本信息】 江南大学 ， 应用化学， 2010， 博士

【摘要】 离子液体作为一种新型的绿色材料,具有不挥发、不可燃、可重复利用、热稳定性好、物化性质可调等特点,已成功地用于有机合成、生物催化、分离提取、电化学等领域。现有的应用最为广泛的离子液体为烷基甲基咪唑盐,然而其设计性差、极性大、憎水性弱、有机性能低的缺陷限制了其在工业上的进一步应用。因此设计开发新型的、具有特殊功能的离子液体材料来满足不同的需求并丰富离子液体基础化学理论,具有重要意义。本文设计合成了13种未见报道的新型烷基咪唑离子液体,其结构和组成被红外、核磁、质谱分析所证实,阳离子为1,3-二烷基咪唑[D(R)Im],阴离子包括PF6-和NTf2-。改进后的程序升温法提高了离子液体的合成产率,离子液体粗品用丙酮稀释后,活性炭脱色制得无色离子液体,产品在400-800 nm范围内无明显吸收,合成机理研究发现中间体1,3-二烷基咪唑溴化盐的合成是关键的控速步骤。芘荧光探针测得新型离子液体极性小于传统丁基甲基咪唑盐。首次采用紫外吸收光谱法测定离子液体在水中的溶解度,发现新型离子液体本身含水量和水中溶解度均比传统甲基烷基咪唑类低1-2个数量级,具有更强的疏水性能。此外,测定了离子液体热稳定性、密度、粘度和表面张力等物理化学性质,并对离子液体结构和性质两者关系的规律性变化进行系统研究。结果表明：离子液体的性能是由阴、阳离子的结构和性质共同决定的。热稳定性、密度、粘度和溶解性主要受阴离子种类影响；随着咪唑阳离子取代基链长的规律性增加,离子液体的热稳定性、密度、极性、水含量和表面张力逐渐降低；首次考察了同分异构离子液体结构对性质的影响。热分解温度均高于320℃；密度介于1.1-1.3g.cm-3之间；表面张力高于传统有机溶剂正已烷,低于水的表面张力。考察了离子液体在香精香料酶法合成中的应用。以假单胞菌脂肪酶Pseudomonas cepacial lipase酶催化合成乙酸苯乙酯为模型反应,考察介质结构和性质对酶催化行为的影响。结果表明离子液体的极性、阴离子种类可显著影响脂肪酶的活性。同分异构离子液体介质中,酶在带有支链的介质中显示了高的催化特性；荧光光谱进一步揭示反应的初始反应速率和产率随介质的极性呈现规律性变化,极性越低,酶活性越高；阴离子为PF6-和NTf2-的疏水性离子液体中反应的初始反应速率和产率明显高于BF4-和C1-类水溶性离子液体中。筛选发现酶在离子液体在[D(2-mb)Im][PF6]中具有最高的催化活性,通过对影响产率的各种因素考察,得到合成乙酸苯乙酯的最佳反应条件(35℃,30 mg酶,1.0 g离子液体,48 h反应时间和1.44%含水量),在此条件下,乙酸苯乙酯的产率达92.3%,初始反应速率为0.0138μmol·h-1·mgprot-1,半衰期为522 h是正已烷中的7.4倍,脂肪酶重复使用10次后催化活性没有明显减少。考察离子液体在仲醇酶法拆分中的应用。以脂肪酶催化拆分1-苯乙醇为模型反应,分别考察介质、水含量和温度对拆分反应的影响。结果表明,在1,3-二异丁基咪唑六氟磷酸盐([D(i-C4)Im][PF6])离子液体介质中酶的活性和反应性明显高于其他离子液体和正已烷,因此,[D(i-C4)Im][PF6]被确定为反应介质。在最佳条件下,初始反应速率为1.93μmol.mg-1.min-1,1-苯乙醇的转化率达50%,对映体过量值eep>99%,酶的半衰期为348 h,酶重复使用10次后活性没有明显减少。此外,光学显微镜研究表明酶在离子液体中以天然的球形状态存在,具有好的活性和热力学稳定性；酶在不同介质中保温6天后的荧光光谱揭示,离子液体[D(i-C4)Im][PF6]介质中,酶结构中氨基酸残基的裸露程度略有增加,但其二级结构仍保持稳定,显示了比有机溶剂更好的结构稳定性；圆二色光谱指出酶蛋白二级结构中的p-折叠含量在酶维持活性构象中发挥了重要的作用。由于在离子液体中游离酶反应后不易回收,所以进行了自制固定化酶的研究并探讨了其在离子液体中的催化性能。在超顺磁球Fe304的基础上通过物理或化学修饰的手段建立了三种不同的脂肪酶固定化方法：Fe304共价结合法、Fe304/CS共价结合法和Fe304/CS吸附包埋法。考查了固定化酶应用于离子液体反应体系的特点,发现Fe304/CS吸附包埋法固定化酶催化的反应体系具有高的初始反应速率和转化率。在优化条件下1-苯乙醇转化率达到49.7%,对映体过量值eep>99%,固定化酶的半衰期达到373 h,酶重复利用15次活性没有明显减少,实现了离子液体中酶的快速分离及循环使用,并避免了有机溶剂萃取剂的使用。考察离子液体在萃取分离中的应用。以离子液体C4)Im] [PF6]、[D(n-C5)Im] [PF6]、[D(n-C8)Im][PF6]和[n-C4MIm][PF6]为溶剂,建立一种简便可靠的水样中超痕量铅的富集方法；优化了1000 mL水样中20μg铅的萃取和反萃条件：螯合剂双硫腙用量5.0 mL、20%的盐酸羟胺溶液加入量1.0mL、0.03 mol.L-1氨水2.0 mL、萃取时间4min、离子液体5.0 mL、铅的最大饱和吸附容量为25μg、1.0 mol.L-1硝酸溶液5.0 mL用于萃取液中铅的剥离反萃；三种新型疏水性离子液体都显示了很高的萃取率(>98.7%)和反萃率(>99.9%),这主要是由于离子液体憎水性性强的原因；建立离子液体萃取体系,方法线性范围是0-100 ng.L-1,检出限为1.0 ng.L-1；干扰试验结果显示大部分的正负离子均不会对检测产生干扰；样品检测回收率在97-102%；离子液体可重复利用5次。机理研究表明铅体系的萃取机理是水溶液中的离子对机理和有机极性分子的相似相溶原理的结合。综上,新型离子液体具有极性温和、憎水性强、有机性能增强等特点,在非水生物催化和液液萃取中展现出了良好的应用前景。除此之外,研究成果可应用于生物仿生合成、微反应器、生命大分子萃取分离等方面的研究。更多还原

【Abstract】 Recently, ionic liquids research has become a new field of green chemistry. Due to their favorable properties such as negligible vapour pressure, non-inflammability, reusability, high thermal stability and favorable and easily tunable physical and chemical properties, ionic liquids technology has been successfully applied to many areas of organic synthesis, biocatalysis reaction, separation process, electrochemistry etc.. However, the select of ionic liquids for special application is also very limited now. At present, main ionic liquids used in various biocatalysis reactions are 1-alkyl-3-methylimidazolium hexafluorophosphate abbreviated as [Cxmim][PF6]. Howener, the defaults of strong polarity, hydrophobicity and poor organic property has limited its application. Herefore, with the development of ionic liquids, more and more ionic liquids with special function are required to satisfy the various demands and enrich the fundamental theory of ionic liquids.13 novel alkylimidazolium ionic liquids were designed and synthesized and the results of the IR,1H-NMR and ESI-MS analysis confirmed the structure and composition of the ionic liquids. The cations mainly consist of 1,3-dialkylimidazolium [D(R)Im], the anions mainly consist of PF6ˉand NTf2ˉ. The modified two-step method using temperature programmed technologies was developed for improving the synthetic yields. After the crude products were diluted by acetone, it was decolored with activated carbon and almost colorless ionic liquids were obtained. There was no obvious absorption peak in the wavelength range of 400～800 nm. Moreover, Mechanism study showed that synthesis of 1,3-dialkylimidazolium bromide was the key rate-determining step. Polarity of ionic liquid was determined by pyrene fluorescence probe and was smaller than traditional ionic liquid; We determined the solubility of ionic liquids in water by ultraviolet absorption spectrum method firstly. And found water content and solubility in water were lower than 1-2 orders of magnitude. Besides, the physical properties containing thermal stability, density, viscosity and surface tension were determined. The relationship between structures and properties of ionic liquids were also studied. The results showed the properties were decided by both cations and anions of ionic liquids and exhibited how melting point, viscosity, density and surface tension were affected by changes in alkyl chain length and configuration. In the series of ionic liquids studied here, changes in spatial configuration of the alkyl had a more dramatic effect on melting point and viscosity of ionic liquids than changes in alkyl chain length, while the latter change had a stronger influence on water content existed in dried ionic liquids, densities and surface tension of them. All these ionic liquids exhibited excellent thermal stability of 320℃; density was of 1.1～1.3g.cm-3; surface tension lower than water and higher than hexane.The application of ionic liquid in enzymatic synthesis of flavors and fragrances was examized. The synthesis of phenylethyl acetate catalyzed by Pseudomonas cepacial lipase was selected as mode reaction to investigate effect of different medium containing structure and property on catalysis performance of the lipase. It was found activity and reactivity of the lipase affected by configuration structure, polarity and anion species of ionic liquids. Among ionic liquid isomers medium, lipase exhibited higher catalysis activity in these ionic liquids containing branched chains. Fluorescence spectrum exhibited the lipase showed higher activity with the decreasing of polarity. Higher initial reaction rate and yield of the reaction were exhibited in ionic liquids containing PF6ˉand NTf2ˉthan BF4ˉand Clˉ. By investigating the influence of various factors on the yield of product, [D(2-mb)Im][PF6] was the best. The optimal conditions for synthesis of phenylethyl acetate were obtained. These were reaction temperature of 35℃, the amounts of lipase of 30 mg, the ionic liquid of 1.0 g, reaction time of 48 h and water content of 1.44%. Under the optimal conditions, the yield and initial reaction rate was up to 92.3% and 0.0138μmol·h-1·mgprot-1. Also, the stability of the lipase in the [D(2-mb)Im][PF6] medium were 522h and as same as 7.4-fold that in hexane. The lipase in the [D(2-mb)Im][PF6] medium was recycled 10 times without substantial diminution in activity.The application of ionic liquid in enzymatic resolution of secondary alcohol was examized. The resolution of (R,S)-1-phenylethanol by Pseudomonas cepacial lipase in six isomer ionic liquids was chosen as the model reaction to study on effects of the reaction medium, water content and temperature on the reaction. The results showed the activity of lipase in the ionic liquid 1,3-di-isobutylimidazolium hexafluorophosphate abbreviated as [D(i-C4)Im][PF6] had obviously better activity and reactivity than those in other ionic liquids and hexane. Accordingly, the ionic liquid [D(i-C4)Im][PF6] was chosen as the medium for the reaction. Under optimal condition, initial rate of lipase, the conversion of 1-phenylethanol, ee value of (R)-1-phenylethyl acetate and half life time of the lipase were 1.93μmol.mg-1.min-1, 50%,99% and 348 h, respectively. Moreover, optical microscope analysis demonstrated lipase existing as native ball enzyme conformation in ionic liquids, and having a higher activity and thermal stability. Fluorescence spectrum showed that after the incubation of lipase in the ionic liquid [D(i-C4)Im][PF6] for six days, the lipase exhibited an slightly increasing exposure level of amino-acid residue, however, its secondary structure is of excellent stability than hexane medium. Circular dichroism pointed the activity and stability was mainly influenced by the content of (3-sheet.Immobilization of lipase from PCLwas also investigated because of the difficulties in lipase recycle in ionic liquids. Superparamagnetic particles Fe3O4 were used as immobilization support both in physical and chemical modified methods:Fe3O4 covalent modification, Fe3O4/CS covalent modification and Fe3O4/CS coated with chitosan. Optically active of 1-phenylethanol was examined in ionic liquid using immobilized PCL as a biocatalyst. Fe3O4/CS coated with chitosan was chosen as the best due to its highest initioal reaction rate and conversion. Under optimal condition, the conversion of 1-phenylethanol, ee value of (R)-1-phenylethyl acetate and half life time of the lipase were 49.7%,99% and 373 h, respectively. The immobilized lipase in the [D(i-C4)Im][PF6] medium was recycled 15 times without substantial diminution in activity.The application of ionic liquid in extraction was examized. A simple and reliable procedure was developed for preconcentraion of ultratrace lead ion in water sample using room temperature ionic liquids [D(n-C4)Im][PF6]、[D(n-C5)Im][PF6]、[D(n-C8)Im][PF6] and [n-C4MIm][PF6] as novel solvents. Lead ion reacted with dithizone to form neutral lead-dithizone complex in 0.03 mol.L-1 ammonia solution, then the complex was extracted into the ionic liquid from aqueous phase and back-extracted with 5 ml of 1.0 mol.L-1 nitric acid rapidly, and the solution was directly used to determine lead concentration by graphite furnace atomic absorption spectrometry(GFAAS). It was found that [D(C4-8)Im][PF6] all gave an excellent solvent characterists in the extraction of ultratrace lead due to its good hydrophobic character and lower melting point and selected, its extraction and back-extraction efficiencies were 98.7 and 99.9% for 20μg standard lead ion in 1000 ml of water sample, respectively. The calibration graph using the preconcentration system for lead was linear with a correlation coefficient of 0.999 at levels near the detection limits up to at least 0.1μg 1-1. The detection limit, calculated using three times the standard error of estimate of the calibration graph, is 1.0 ng of lead per liter water sample. Proposed procedure allows the rapid lead determination at 100 ng.L"1 level in environmental water with satisfactory results. The interference study indicated the determination of lead was free from the interference of almost all positive and negative ions found in water. Lead recoveries between 97 and 102% for spiked samples proof the accuracy of the proposed method. Moreover, the reuse of ionic liquid was up to 5 times. The extraction mechanism of system was combination of ions pairs theory and similar dissolve mutually theory in aqueous solvent.On account of the kind polarity, strong hydrophobicity and favorable organic properties, this new class of ionic liquids has found a place as suitable alternatives to volatile organic solvents in nonaqueous biocatalysis and liquid/liquid extraction. Besides, the study will have wide application perspective in biomimetic synthesis, microreactor technology, biomacromolecule extraction and separation.更多还原