Premium
A kinetic study of the reduction of toluidine blue with thiourea in acidic solution
Author(s) -
Jonnalagadda S. B.,
Tshabalala D.
Publication year - 1992
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.550241110
Subject(s) - chemistry , thiourea , toluidine , hydrochloric acid , activation energy , aqueous solution , kinetic energy , enthalpy , one electron reduction , inorganic chemistry , stoichiometry , ion , order of reaction , kinetics , reaction rate constant , organic chemistry , electrochemistry , electrode , physics , quantum mechanics
A detailed kinetic study of the reaction of toluidine blue (tolonium chloride) (TB + Cl − ) with thiourea (TU) in aqueous hydrochloric acid solution is reported. The reaction was first order with respect to toluidine blue and the reductant and second order with respect to [H + ]. Thiourea had a 2:1 stoichiometric ratio with TB + . Toluidine blue was reduced to a colorless base in two one‐electron reduction steps and TU was oxidized to thioformamidinium ion, which dimerized rapidly to give stable dithioformamidinium ion. The energy parameters obtained for TB + ‐TU reaction were mean energy of activation ( Ea′ ) = 26.7 ± 2.4 kJ M −1 ; enthalpy of activation (Δ H # ) = 24.2 kJ M −1 ; frequency factor (A) = 1.04 × 10 4 M −3 s −1 ; and entropy of activation (Δ S # ) = −176.35 J M −1 s −1 . © John Wiley & Sons, Inc.