Editor-in-Chief Hatice Kübra Elçioğlu Vice Editors Levent Kabasakal Esra Tatar Online ISSN 2630-6344 Publisher Marmara University Frequency Bimonthly (Six issues / year) Abbreviation J.Res.Pharm. Former Name Marmara Pharmaceutical Journal
Marmara Pharmaceutical Journal 1989 , Vol 5 , Issue 1
The formation and stability of 3,4-diaminobenzenesulfonic acid -iron (III) complex
Gönül Yüksel,Mürşit Pekin,Emre Dölen
In this work, the formation conditions of the red-brown (Δ=450 nm) complex which was formed from 3-4-diaminobenzensulfonic acid (DAB) and iron (III) were studied and stability constant determined spectrophotometrically. The acid constant of ligand was determined potentiometrically and found as pKa=3.413+-0.201 at 20oC. by using the Job’s method of continuous variation, the composition of complex was found as Fe(III)/DAB=3/2 at pH=4.00. From mole ratio curve were observed two inflection points for Fe(III)/DAB=1/2 abd 3/2. When was determined iron(III) in the solution was prepared as Fe(III)/DAB mole ratio equal to 3/2 titrated by standard EDTA solution was found that only one third of total iron at iron(III) oxidation state. Thus, two third of total iron oxidizes the equivalent amount of DAB to monoamine molecules. The formula of the soluble complex may be [Fe(DAB)2(H2O2)]+. The formation constants of complex were found as K=8.20.107 (log K=7.914) by using ligand excess method and K= (2.907±0.436)107 (logK=7.464) by using equal absortive solutions method for 20oC and I=0.125. The free energy change in the formation of complex is ΔG=41.86 kj.mol-1. Keywords :
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