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Kinetics and mechanisms of substitution reactions with sulfur‐containing nucleophiles in aqueous acid solutions. I—rates of reactions of some tetrahalopalladate (II) anions with thiourea and selenourea
Author(s) -
Van Z. Bekker P.,
Robb W.
Publication year - 1975
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550070110
Subject(s) - chemistry , thiourea , aqueous solution , reaction rate constant , entropy of activation , substitution reaction , halide , nucleophile , ligand (biochemistry) , kinetics , sulfur , medicinal chemistry , inorganic chemistry , activation energy , rate equation , reaction rate , catalysis , organic chemistry , biochemistry , physics , receptor , quantum mechanics
The activation energy parameters for the reaction of PdX 4 2−(X=Cl − , Br − ) in aqueous halide acid solution with thiourea (tu) and selenourea (seu) have been determined. High rates of reaction parallel low enthalpies and appreciable negative entropy of activation. The rate law in each case simplifies to k obs = k [L] where L=tu or seu, and only ligand‐dependent rate constants are observed at 25°C. The ligand‐dependent rate constants for the first identifiable step in the PdCl 4 2−+ X system is (9.1±0.1) × 10 3 M −1 sec −1 and (4.5±0.1) × 10 4 M −1 sec −1 for X=tu and seu, respectively, while for the PdBr 4 2−+ X system it is (2.0±0.1) × 10 4 M −1 sec −1 and (9.0±0.1) × 10 4 M −1 sec −1 for X=tu and seu, respectively.