N-羧基吡啶功能化离子液体的表征

合成了系列新型N-羧基吡啶功能化离子液体, 利用1H NMR、13C NMR、IR、DSC对其进行表征并研究了其与常规溶剂的相溶性, 采用酸碱滴定法测量了系列离子液体的酸离解常数pKa值. N-羧基取代吡啶功能化离子液体的pKa值在2.5~4.0之间, 并随阳离子取代羧基碳链的增长而增大; 离子之间形成氢键及阴、阳离子的大小是影响离子液体熔点的主要因素. 阴离子越小, 熔点越高. 所合成的N-羧基吡啶功能化离子液体具有相同的相溶性且由取代羧基所决定, 与常见烷基咪唑离子液体相比, N-羧基吡啶功能化离子液体与丙酮、二氯甲烷并不相溶. 功能化离子液体的阳离子取代基是影响其物化性能的主要因素, 通过改变功能化基团碳链的长短及与不同阴离子进行组合, 可以对功能化离子液体物理、化学性能进行调节.

Characterization of N-carboxyl Appended Pyridine Task-Specific Ionic Liquids

A series of N-carboxyl appended pyridinium task-specific ionic liquids(TSILs) were synthesized and characterized by 1H NMR, 13C NMR, IR, and DSC. The miscibilities of these TSILs with conventional solvents were studied and the acid-dissociation constant pKa values of them were measured through titration. The pKa values of N-carboxyl appended TSILs were between 2.5 to 4.0 and increased with increasing alkyl chain length. The melting points of N-carboxyl appended TSILs were influenced extensively by the size of ions and hydrogen bonds formed between the ions, the smaller the anion size is, the higher the melt point is. With conventional organic solvents, the miscibilities of all synthesized N-carboxyl appended TSILs were the same and mainly determined by the substituted carboxyl. Con-trary to common imidazolium ILs, N-carboxyl appended TSILs were immiscibe with acetone and dichloromethane. The physical properties of TSILs were mainly affected by the substituted group and could be adjusted with task-specified cation, changing the length of substituted group, or combining of the selected cation and anion.