A solid state and solution NMR study of the tautomerism in hydroxyquinoline carboxylic acids.
Some hydroxyquinoline carboxylic acids and their conjugate acids and bases were characterized by 13C and 15N NMR spectroscopy in solution and in the solid state. Differences in 13C and, in particular, 15N chemical shift patterns allow to distinguish between individual tautomers and confirm the presence of zwitterionic species in the solid state. Solution NMR spectra in dimethyl sulfoxide (DMSO) show effects resulting as a consequence of dynamic exchange and suggest the presence of an equilibrium mixture of hydroxyquinoline carboxylic acid and zwitterionic hydroxyquinolinium carboxylate tautomers.
Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart, Germany. gudat@iac.uni-stuttgart.de
Dietrich
D
Gudat
Jacek E
JE
Nycz
Jaroslaw
J
Polanski
D002247:Carbon Isotopes; D002264:Carboxylic Acids / Q000737:chemistry*; D004121:Dimethyl Sulfoxide; D006912:Hydroxyquinolines / Q000737:chemistry*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009587:Nitrogen Isotopes
D002247:Carbon Isotopes; D002264:Carboxylic Acids; D006912:Hydroxyquinolines; D009587:Nitrogen Isotopes; D004121:Dimethyl Sulfoxide