Abstract
Proton transfer (PT) reaction between 2-aminopyridine (2AP) with 2,6-dichloro-4-nitrophenol (DCNP) has been investigated spectrophotometrically in methanol (MeOH), acetonitrile (AN) and acetonitrile with 1,2-dichloroethane binary mixtures (1:1, ANDEI) and (3:1, ANDEII). A long wavelength band in the range 395-424 nm due to the proton transfer complex formation has been recorded. The formation constants of the PT-reaction (K-PT.) have been estimated using Benesi-Hildebrand equation. It has been found that K-PT recorded larger value in AN than MeOH and binary mixtures. This result was interpreted in terms of solvatochromic parameters like, solvent polarizability (pi*), hydrogen bond donor (alpha), and hydrogen bond acceptor (beta). The molecular composition of the PT-complex has been identified by Job's and photometric titration methods where 1:1 complex is formed. Based on the rapidity and simplicity of the PT-reaction as well as the stability and simple composition of the formed complex, a rapid, accurate and sensitive spectrophotometric method for determination of 2AP was proposed. In addition, the solid FT-complex (2AP-DCNP) has been isolated and characterized using elemental analyses and FTIR measurements. (c) 2010 Elsevier B.V. All rights reserved.