Deprotonation of beta-cyclodextrin in alkaline solutions.
Variable pH (13)C NMR and (1)H NMR spectroscopic studies of the beta-cyclodextrin (beta-CD) in alkaline aqueous solutions revealed that beta-CD does not deprotonate at pH<12.0. Further increase in solution pH results in the deprotonation of OH-groups adjacent to C-2 and C-3 carbon atoms of beta-CD glucopyranose units, whereas the deprotonation of OH-groups adjacent to C-6 carbon atoms is expressed less markedly. The pK(a) values for beta-CD OH-groups adjacent to C-2 and C-3 carbon atoms are rather close, pK(a1,2) being 13.5+/-0.2 (22.5 degrees C).
Gaidamauskas
Ernestas
E
Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA.
Norkus
Eugenijus
E
Butkus
Eugenijus
E
Crans
Debbie C
DC
Grinciene
Giedre
G
D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D011522:Protons; D047392:beta-Cyclodextrins / Q000737:chemistry*
D011522:Protons; D047392:beta-Cyclodextrins