1-烷基-3-甲基咪唑硫酸氢盐的物理性状研究

合成了系列酸性离子液体1-烷基-3-甲基咪唑硫酸氰盐（CnMIm]HSO4，n=0，2，4，6，8），并用FT-IR和^1H NMR表征其结构．测定了其密度、黏度、溶解性、酸度、电导率和热稳定性等物理性质，考察了不同烷基对物理性状的影响．结果表明，密度随咪唑环上烷基的增长而减小；由于受氢键与范德华力的共同作用，使C4MIm]HSO4的黏度最小，其数值为16．359×10^-3Pa·s；在水溶液中，CnMIm]HSO4的极限摩尔电导率均高于KCl，其中以C4MIm]HSO4的极限摩尔电导率最大，其数值为570．93S·cm^3·mol^-1；在氢键和空间效应的共同影响下，使C6MIm]HSO4的pKa最小，其数值为0．695；离子液体的溶解度与溶剂的极性有关，易溶于强极性溶剂，难溶于弱极性溶剂；CnMIm]HSO4在低于240℃具有良好的热稳定性．

Physical Properties of 1-Alkyl-3-Methylimidazolium Hydrosulfate

Five ionic liquids,namely,1-alkyl-3-methylimidazolium hydrosulfate(CnMIm]HSO4;alkyl includes ethyl,butyl,hexyl and octyl),were synthesized and characterized by 1H NMR and FT-IR spectra.The physical properties including solubility,density,viscosity,thermostability,conductivity,pKa were measured.The results showed that the alkyl chain length had the most dramatic effect on the properties.The density of CnMIm]HSO4 decreased with increasing length of alkyl in imidazole;Their viscosities are interrelated with length of alkyl in imidazole,and the viscosity of C4MIm]HSO4 was the lowest(16.359 10-3Pa · s);Because of the effect of hydrogen bond and Van Der Waals forces,the pKa of C6MIm]HSO4 was the least(0.695);The limiting molar conductivity of CnMIm]HSO4 was more than that of KCl,and the limiting molar conductivity of C4MIm]HSO4 was the highest(570.93 S · cm2 · mol-1);Their solubility depends on the polarity of the solvents,and they were easy to dissolve in higher polarity solvents ;They were stable at temperatures lower than 240 ℃ and behave as Newtonian fluids.