The formation rate of the 1:1 iron(III) complex with 4-isopropyltropolone (Hipt) has been studied spectrophotometrically in aqueous solution of low pH at various temperatures and pressures by a stopped-flow technique. The rate law is expressed as d[Fe(ipt)2+]/dt = (K1 + K2KFeOH[H+]-1)(1 + KH[H+])-1[Fe3+][Hipt], with k1 = 21.7 ± 1.1 M-1 s-1 and k2 = (6.30 ± 0.31) × 103 M-1 s-1 at 25 °C and I = 1.00 M at atmospheric pressure. The activation parameters for the reaction of Fe(OH2)63+ (k1 path) and the reaction of Fe(OH2)5OH2+ (k2 path) are as follows: ΔH‡1 = 59.5 ± 3.0 kJ mol-1, ΔS‡1 = -19.8 ± 3.0 J mol-1 K-1, ΔV‡1 = -8.7 ± 0.8 cm3 mol-1; ΔH‡2 = 29.2 ± 3.6 kJ mol-1, ΔS‡2 = -72.3 ± 5.0 J mol-1 K-1, ΔV‡2 = 4.1 ± 0.6 cm3 mol-1. Associative- and dissociative-interchange mechanisms are most probably operative for the k1 and k2 paths, respectively.
|Number of pages||5|
|Publication status||Published - 1983 Jan|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry