NDLI: Solvent effect on the proton-binding sites in urocanic acid. A tautomeric equilibrium study.

Content Provider	Semantic Scholar
Author	Halle, Jeffrey C. Pichon, Clotilde Terrier, François
Copyright Year	1984
Abstract	A 1H NMR study of urocanic acid dissolved in water/dimethyl sulfoxide mixtures together with potentiometric determinations of its two successive acidities in the same solutions reveal that a proton is transferred from the imidazolium ring to the carboxylate group when the amount of dimethyl sulfoxide is increased. An analysis of the potentiometric data by means of the classical Hammett linear relationship allowed the four microscopic acidity constants to be determined. At 20 degrees C, there are equal fractions of the tautomeric species, i.e. urocanic acid (AH0) and its zwitterion (AH+-) in the mixture containing 34% dimethyl sulfoxide by weight (congruent to 0.1 in mole fraction), while 50% dimethyl sulfoxide by weight (congruent to 0.2 in mole fraction) is necessary to completely bias the equilibrium: AH+- in equilibrium AH0 toward the molecular form AH0.
File Format	PDF HTM / HTML
PubMed reference number	6706996
Journal	Medline
Volume Number	259
Issue Number	7
Alternate Webpage(s)	http://www.jbc.org/content/259/7/4142.full.pdf
Journal	The Journal of biological chemistry
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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