Study of equilibria and kinetics of the acid catalysed interaction of iron(III) with salicylaldehyde ando-hydroxyacetophenone |
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Authors: | Asim K Das |
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Institution: | 1. Sir Rashbehari Ghose Laboratory, Department of Chemistry, University College of Science, 700 009, Calcutta, India
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Abstract: | The equilibria and kinetics of the reaction of FeIII with salicylaldehyde ando-hydroxyacetophenone, leading to 1∶1 chelate formation, have been studied at different temperatures (25–35°C) and ionic strength,
I = 1.0 mol dm−3 (NaClO4+HClO4). A dual path mechanism involving both Fe
aq
3+
and Fe(OH)
aq
2+
species and undissociated free ligand (LH) is consistent with the experimental observations where H+]≫Fe]T≫L]T (where Fe]T and L]T stand for total concentrations of iron and ligand respectively). The results conform to kobs/B = k1H+]+k2Kh where B = Fe]T/(Kh+H+])+1/Q; Kh = hydrolysis constant of Fe
aq
3+
; k1, k2 are the forward second order rate constants of Fe
aq
3+
and Fe(OH)
aq
2+
, respectively, and Q is the equilibrium constant of the reaction, Fe3++LH⇋FeL2++H+. Thermodynamic parameters for each of the steps have been determined. Fe(OH)
aq
2+
appears to react in a dissociative fashion (Eigen-Tamm mechanism), whilst Fe
aq
3+
appears to react through the associative inter-change (Ia) mechanism. The equilibrium constants (Q) obtained spectrophotometrically are compared with those obtained from kinetic studies.
TMC 2638 |
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Keywords: | |
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