Kinetics of electron transfer reaction in micellar and reverse micellar media: Reduction of [Co(NH3)5N3]Cl2 by iron(II)

Electron transfer reaction of pentaammineazidocobalt(III)chloride with ferrous salt has been investigated in cationic normal micellar media of N-cetyl-N,N,N trimethyl ammonium bromide (CTAB) and also in well-characterized, monodispersed biomimicking nanocavities formed by anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in n-heptane/water using spectrophotometric methods. The rate law and mechanism of the reaction is same in both continuous water pool, in presence of cationic micelle of CTAB and in water pool in micellar cavity. The reaction rates depend on the interphase environment of micelle and reverse micelle. The reaction rates are also very much dependent upon the water to surfactant mole ratio (W), i.e., on the water pool size of the reverse micellar cavity. Rate of the reaction as well as observed pseudo-first-order rate constant (kobs) decreases with W. Dependence of rate with W is of a non-linear pattern. The micellar interface of nanosized water pool plays important role to influence rate of the reaction.