Abstract

Asha Mathew¹, P.Shyamala² and A.Satyanarayana²

DOI : http://dx.doi.org/10.13005/ojc/360323

Acid-base equilibria of 1-(2-Pyridylazo)-2-naphthol (PAN) in neutral, cationic and anionic micellar media are investigated by potentiometric method using Calvin-Wilson titration technique. Best fit chemical models obtained using MINIQUAD-75 program showed the presence of both mono-protonated (LH22+) and deprotonated (L-) species of PAN (LH) in solution. The equilibrium constants β011 and β012 corresponding to the formation of LH and LH2+ species respectively from the most anionic form (L-) of PAN at a temperature of 30.0 ± 0.1 0C and an ionic strength of 0.1 mol.dm-3 are reported. Several interesting results emerged from the study of the affect of the neutral and charged micelles on the equilibria are explained on the basis of the pseudo phase ionic exchange model, dielectric constant, polarity, hydrophilic and hydrophobic properties of micelles. Species distribution diagrams are generated using HYSS program.

Chemical Speciation; CTAB; formation constants; micelles; PAN; SDS; TX-100

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