Kinetic study of an autocatalytic reaction: nitrosation of formamidine disulfide

Abstract

The reaction kinetics for the acid nitrosation of formamidine disulfide (FDS) show an autocatalytic behavior that arises from the fact that the thiocyanate ion formed as a product acts as a powerful catalyst for the nitrosation reaction. In the presence of added nucleophiles the suppression of the autocatalytic route results from competition for the nitrous acid between the added halides and the thiocyanate anion, which is formed as a reaction product. Analysis of the kinetic data enabled extraction of the bimolecular rate constants, Kinetic results are consistent with the attack on the nitrosating agent as the rate limiting step, i.e., the nitrosation of FDS behaves in a similar manner to the nitrosation of an amine. Rather different behavior is found for other substrates with an imino moiety adjacent to an amino nitrogen, such as the guanidines, which react by a mechanism in which the rate limiting step is the reorganization of the nitrosated substrate.

Autocatalysis: Kinetics, Mechanisms and Design

“…SCN − acts as an autocatalyst. It reacts with HNO 2 , affording NOSCN, which is a powerful nitrosylating agent [62] …”

“…It reacts with HNO 2 , affording NOSCN, which is a powerful nitrosylating agent. [62] Oxidation reactions by Co(III) form another class of autocatalytic reactions. The oxidation of hydrazine by carbonatocobaltate(III) is the first example.…”

Electrooxidation of Formamidine Disulfide Simultaneously Investigated by On‐Line High Performance Liquid Chromatography and Cyclic Voltammetry

“…[6][7][8][9] As an intermediate of such processes, the TU 2 2 + exhibits different valence changes and various products, including oxides and free radicals, as well as the occurrence of autocatalytic and hydrolysis reactions. [10][11] A. E. Bolzán et al applied voltammetry and rotating ringdisk electrode techniques to study electrochemical response of thiourea and formamidine disulphide on polycrystalline platinum electrode. The electro-oxidation of thiourea on platinum involves two stages occurring in different potential windows, yielding soluble formamidine disulphide as the main product.…”

“…[ 6 , 7 , 8 , 9 ] As an intermediate of such processes, the TU 2 2+ exhibits different valence changes and various products, including oxides and free radicals, as well as the occurrence of autocatalytic and hydrolysis reactions. [ 10 , 11 ]…”

“…A variety of studies have shown that abundant nonlinear dynamical phenomena occur in the TU oxidation process [6–9] . As an intermediate of such processes, the TU 2 2+ exhibits different valence changes and various products, including oxides and free radicals, as well as the occurrence of autocatalytic and hydrolysis reactions [10–11] …”