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Zwitterionic pyridinecarboxylic acids
Author(s) -
García Begoña,
Ibeas Saturnino,
Leal José M.
Publication year - 1996
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199609)9:9<593::aid-poc593>3.0.co;2-7
Subject(s) - chemistry , zwitterion , potentiometric titration , protonation , picolinic acid , isonicotinic acid , nicotinic acids , base (topology) , cationic polymerization , inorganic chemistry , medicinal chemistry , organic chemistry , nicotinic agonist , biochemistry , ion , receptor , mathematics , molecule , mathematical analysis , hydrazide
A study of the acid‐base behaviour of the three isomeric pyridinecarboxylic acids (picolinic, nicotinic and isonicotinic acid) was carried out using spectrophotometric and potentiometric measurements. The cationic form of picolinic acid converts partially into the corresponding zwitterion (p K 1 ) within a borderline acidity range where neither the pH scale nor the acidity functions work satisfactorily. Protonation of the carboxyl groups (p K 3 3) occurred at the highest acidity levels employed. The medium effects observed on the spectral curves were corrected by factor analysis. The potentiometric measurements gave values for p K 1 and p K 2 only, which were in good agreement with those determined spectrophotometrically.