Extension Of PKa Scale In Ionic Liquids And Study On Adhesion Of Azo Acid And

Ionic liquids (ILs) as possible "green" replacement for volatile organic solvents have been extensively used in organic synthesis, catalysis and separation etc. However, little is known about key fundamental issues of ILs, for example, Are there generic ILs properties? What kinds of fundamental properties of ILs have the qualitative and/or quantitative relationships with their anions and cations? How the use of an ILs can affect the reactivity of solute species? The ionization constant pKa is a quantitative measure of the strength of an acid in solution, depends on the ability of the solvent to solvate the proton, the anion, and the undissociated acid. The pKa scales of many molecular solvents have already been reported, which provide a fundamental data base for assessment·of the electronic and steric effects brought about by structural variations in organic molecules. ILs as solvents for the acidity scale to be established is in infancy, nonetheless many pKa data must be experimentally measured for practical application and theoretical research.In recent years, Our group have been interested in the research of physical organic chemistry based on the acidity scale of ILs, and developed a general approach to measure absolute pKa data in ILs, then an absolute pKa scales in ILs has also been established for the first time. In this thesis the acidity scales in ILs have been expanded, the absolute pKa scales of N-H acids and Ylides have also been established.(1) Expanded the absolute pKa scales. Our previous absolute pKa scales only range of13pKa unit, many important compounds cannot be measured in it. Here we select some picric acid type indicator extend the pKa scales downward into the negative pKa region about3pKa units in [BMPY][NTf2] and [BMIM][NTf2]. After a careful selection of a more stronger base, we extend the pKa scales upward into the positive pKa region about3orders of magnitude in [BMPY][NTf2] and [BM2IM][NTf2]. The comprehensive acidity scale in [BMPY][NTf2] from3,5-diCl-Picric acid to EtSO2CH(Et)SO2Et spanning more than19pKa units. (2) The pKa’s of R-PhNHSO2Ph and R-PhNHTf have been measured in [BMIM][NTf2],[BMPY][NTf2],[BM2IM][NTf2] and [BMIM][OTf]; R-PhCONHTf and R1-PhSO2NHSO2Ph-R2also been determined in [BMIM][NTf2] and [BMPY][NTf2]. Both of the cation and anion moieties of ILs could affect the acidity of N-H acids, Regression analyses demonstrate that all the N-H acids pKa data obtained in different ILs and AN are all linearly correlated to each other.(3) Besides the neutral N-H acids and C-H acids, the first absolute pKa scales of stability phosphonium Ylides and nitrogenium Ylides were constructed in [BMIM][NTf2],[BMPY][NTf2],[BM2IM][NTf2] and [BMIM][OTf]. The results are similar with N-H acids. The acidity of Ylides depends on the cation and anion of ILs. pKa data all have linearly correlated to each other no matter in different ILs or in DMSO.(4) We have measured N-H acids, C-H acids and Ylides acidity scale in ILs, and found that have different solvation model among them. The anion of the ILs can solvate undissociated N-H acids by weak hydrogen bond and solvate Ylides through coulombic interaction; The cation of the ILs can improve more acidity of N-H acids by hydrogen bond than C-H acids.