Open AccessProtolytic equlibria of bromazepam
Author(s) -
B Lidija Pfendt,
G. Popović,
Z Tatjana Damjanovic,
M Dusan Sladic
Publication year - 2002
Publication title -
journal of the serbian chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.227
H-Index - 45
eISSN - 1820-7421
pISSN - 0352-5139
DOI - 10.2298/jsc0203187p
Subject(s) - bromazepam , chemistry , protonation , ionic strength , pyridine , homogeneous , ionic liquid , equilibrium constant , ionic bonding , inorganic chemistry , aqueous solution , medicinal chemistry , ion , organic chemistry , thermodynamics , catalysis , biochemistry , physics , receptor , benzodiazepine
The protolytic equilibria of bromazepam, an ampholyte sparingly soluble in water, in homogeneous and heterogeneous systems were studied in the pH range 0?14 at 25?C and at ionic strength of 0.1 mol/dm3 (NaCl). On the basis of 13C-NMR spectra, the protonation site was predicted ? in acidic media the pyridine nitrogen of bormazepam is protonated. The acidity constants of bromazepam were determined spectrophotometrically (pKa1 2.83 and pKa2 11.60) and potentiometrically (pKa1 2.99). In the heterogeneous system the following equilibrium constants were determined: Ks0 =[HA]?(pKs0 3.44), Ks1 =[H2A+]/[H3O+](pKs1 0.61), and Ks2 =[A-][H3O+](pKs2 15.04).