Part A. Indoaniline dye formation. Part B. Chlorite redox chemistry.

摘要

This dissertation includes two main topics; kinetic and mechanistic studies of the formation of indoaniline dyes, and the kinetics and mechanistic investigation of the redox chemistry of chlorite with sulfur compounds.;The indoanilines and indophenols are formed by a reaction of the corresponding p-benzoquinone imine and the coupler. In the pH range 7--12, the coupling reaction involves an electrophilic attack of the p-benzoquinone imine on the phenol or naphthol resulting in an intermediate leuco-dye, which is rapidly oxidized to give the final indo dye. In the case of unsubstituted and mono-substituted p-phenylenediamines, the rate-determining step involves the coupling between the di-imine and the phenol or naphthol. However, in the di-substituted case there are two different rate-determining steps, a coupler dependent and a coupler independent. The rate constants of a wide range of coupling combinations were determined.;A general kinetic feature has been observed experimentally for the oxidation of the sulfur(-II) species thiosulfate, thiourea, thiocyanate, and sulfide by chlorite and other multi-equivalent oxidants under appropriate, unbuffered batch conditions. This "fingerprint" consists of an initial rise in pH followed by an autocatalytic drop in pH or oligo-oscillatory behavior. These systems also exhibit oscillations and other complex dynamic behavior in a continuous-flow stirred tank reactor (CSTR). We propose a simple, general model that is based upon the changing oxidation states of sulfur to explain the general pH features.;The reaction between sulfur(IV) and various oxidants plays an important role in many non-linear systems. Chlorine dioxide reacts rapidly with sulfite but slowly with bisulfite. The reaction occurs by a one-electron oxidation of the sulfur(IV), apparently forming the sulfur(V) intermediate. This intermediate is then rapidly oxidized by chlorine dioxide to sulfur(VI). Chlorite reacts very slowly with sulfite but rapidly with bisulfite in an acid catalyzed and uncatalyzed reaction. The oxidations by chlorite occur by a 2-electron oxidation, by an oxygen atom transfer between the oxidant and the sulfur(IV). Reaction schemes are proposed that provide satisfactory simulations of the observed kinetic data and estimates of the rate constants for the reactions.