Metal-ion oxidations in solution. Part XV. Rate-determining dimerisations in redox reactions of iron(III) with some α-mercaptocarboxylic acids
- 1 January 1975
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 19,p. 1930-1934
- https://doi.org/10.1039/dt9750001930
Abstract
The kinetics of decomposition of iron(III)–sulphur-bonded complexes with α-mercaptocarboxylic acids (HORSH) have been investigated. A rate-determining dimerisation is considered to take place with a two-electron transfer FeIII+ HORSH [graphic omitted] [FeIII(ORS)]++ 2H+(i), 2[FeIII(ORS)]+ [graphic omitted] 2FeII+ HORS·SROH (ii) leading directly to the disulphide product. The effect of methyl substituents on the ligands suggests an associative mechanism. At 25 °C, for mercaptoacetic acid, k0= 167 ± 18 l mol–1 s–1(ΔH‡= 5 ± 1.5 kcal mol–1, ΔS‡=–31 ± 5.5 cal K–1 mol–1); 2-mercaptopropionic acid, k0= 130 ± 10 l mol–1 s–1(ΔH‡= 9 ± 2 kcal mol–1, ΔS‡=–18 ± 3 cal K–1 mol–1); 2-mercapto-2-methylpropanoic acid, k0= 47 ± 8 l mol–1 s–1(ΔH‡= 14 ± 4 kcal mol–1, ΔS‡=–5 ± 1.5 cal K–1 mol–1); and 2-mercaptosuccinic acid, k0= 68 ± 7 l mol–1 s–1(ΔH‡= 10 ± 1.5 kcal mol–1, ΔS‡=–16 ± 2 cal K–1 mol–1). Apparent differences in the overall rates of the redox reaction with methylation are explicable in terms of variation in the equilibrium constant K1.Keywords
This publication has 0 references indexed in Scilit: