ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Potentiometric and Thermodynamic Studies of 4-Sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one and its Metal Complexes

A. A. Al-Sarawy

Mathematical and Physical Science Department, Faculty of Engineering, Mansoura University, Mansoura, Egypt

E-mail: alsarawy2000@yahoo.com

Received: 7 October 2002

Abstract: The dissociation constant of 4-sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one and metal—ligand stability constants of its complexes with bivalent (Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺) metal ions have been determined potentiometrically in 0.1 M-KCl and 40 vol. % ethanol—water mixture. The order of the stability constants of the formed complexes decreases in the sequence Cu²⁺, Ni²⁺, Co²⁺, Mn²⁺. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The dissociation process is nonspontaneous, endothermic and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, endothermic, and entropically favourable.

Full paper in Portable Document Format: 582a109.pdf

Chemical Papers 58 (2) 109–112 (2004)