Thermodynamic stability constants of complexes of Fe(III)-ion with orciprenaline and phenylephrine

Abstract

The concentration stability constants of Fe(III)-orciprenaline complex and Fe(III)-phenylephrine complex were calculated for three different ionic strengths, by modificated Bjerrum's method. The values of thermodynamic stability constants are determined from curve log β = f (I1/2), as interception at ordinate. From the determined thermodynamic stability constants logβ10 =8,28 and logβ02 = 16,24 of the complexes investigated, the values of the ∆G10= - 46,87 kJ/mol and, AG° = -92,76 kJ/mol were calculated for Fe(III)-orciprenaline and Fe(III)- phenylephrine complexes respectively.

Za komplekse Fe(III)-fenilefrin i Fe(III)-orciprenalin određene su vrednosti koncentracionih konstanti stabilnosti na tri jonske jačine (0,024; 0,050 0,075 mol/dm3). Na osnovu ovih vrednosti izračunate su termodinamičke konstante stabilnosti ovih kompleksa ekstrapolacijom dijagrama logβn=f(I) na vrednost I=0. Dobijena vrednost za kompleks Fe(III)-fenilefrin je logβ0 2 = 16,24, a za kompleks Fe(III)-orciprenalin ona iznosi logβ10= 8,28. Izračunate su promene standardne Gibbsove energije za reakciju stvaranja kompleksa: ∆G1°= -46,87 kJ/mol za Fe(III)- orciprenalin i ∆G°2 = -92,76 kJ/mol za Fe(III)-fenilefrin.