Ionization constants of all seven positional isomers of quinolinesulfonamides and quinoline-N,N-dimethylsulfonamides

• Published in: Journal of molecular structure Vol. 1033; pp. 284 - 288
• Main Authors: Maślankiewicz, Maria J., Marciniec, Krzysztof, Maślankiewicz, Andrzej, Jaworska, Maria
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 06.02.2013
• Subjects: absorbance; ionic strength; ionization; isomers; NBO population analysis; pKa of quinolines; pKa of sulfonamides; spectroscopy; pKa of sulfonamides; NBO population analysis; pKa of quinolines
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2012.10.024

► pKa values of isomeric sulfamoylquinolines as pyridine-type bases were measured. ► pKa values of isomeric sulfamoylquinolines as SO2NH2 acids were determined. ► pKa values of N,N-dimethylsulfamoylquinolines as pyridine-type bases were measured. ► Correlations between pKa data and calculated NBO population values were found. ► pKa values were determined by means of a UV–VIS spectroscopic method. The pKa values of isomeric sulfamoylquinolines 2a–8a and N,N-dimethylsulfamoylquinolines 2b–8b were determined by means of a UV–VIS spectroscopic method that uses absorbance diagrams, at constant ionic strength (0.15M). For sulfamoylquinolines 2a–8a two pKa values – for basic function (Nring: −0.31 to 3.36) and for acid function (SO2NH2 group: 8.89–10.34) but only one in the case of N,N-dimethylsulfamoylquinolines 2b–8b (−0.05 to 3.07) – were obtained. The full geometry optimization in the 6–311+G(d) basis set and the NBO population analysis were performed. Correlation between the experimentally determined and theoretically calculated (Sparc program) of pKa values as well as the differences between the calculated NBO population values for neutral and ionic forms were found for compounds 2a–7a and 2b–8b.