Oscillatory reactions in the lactic acid/acidic bromate system with a tetraazamacrocyclic nickel(ii) complex as catalyst

Abstract

New oscillating reactions with the participation of a tetraazamacrocyclic nickel (II) complex [NiL](ClO 4 ) 2 as catalyst in the lactic acid/acidic bromate system are reported. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11tetraazacyclotetradeca-4,11-diene. The oscillating features are described, and the activation energy is found to be as low as 27.2 kJ/mol. Experimental results suggest that the brominating reaction may take place on pyruvic acid, the oxidized product of lactic acid. A tentative mechanism based on FKN is proposed.

Identification of Two Aliphatic Position Isomers between α- and β-Ketoglutaric Acid by Using a Briggs–Rauscher Oscillating System

“…The periodic change of solution color (yellow-brown-yellow) was noticed during the oscillation. This can be explained by a one-electronic transfer process for catalyst: However, instead of green, brown was observed during the oscillations. The periodic generation of I 2 was responsible for this phenomenon: iodine was produced and dissolved periodically during oscillation.…”

A Novel BriggsRauscher Oscillation with a Macrocyclic Nickel(II) Complex as Catalyst and Pentane‐2,4‐dione as the Substrate

“…During the oscillation, the periodic change of solution color (yellow -brownyellow) was observed. We had expected that yellow and green (NiL 2þ and NiL 3þ ) alternated during oscillating [12]. However, we observed brown instead of green, because I 2 was produced and dissolved periodically during oscillation in the solution, and we will discuss this in detail in Sect.…”

Dynamical regime of resorcinol based Belousov–Zhabotinsky chemical oscillator in the presence or absence of some hydrophobic antioxidants in aqueous–organic mixed media

“…38 Lately, BZ reactions catalyzed by these complexes have attracted much more attention because of their unusual oscillating features, which are reected in lower activation energies, higher oscillating frequencies 39 and being vulnerable to external perturbations. By using macrocyclic Cu (II) or Ni(II) complexes as catalyst, the oscillating reactions involving lactic acid, 40,41 malonic acid, 42 and pyruvic acid 43 45 were determined by perturbations of analyte on the oscillating system. However, all these APP determinations involve substrates which were soluble in aqueous acid media and thus restricted the use of hydrophobic species like vitamins, antioxidants or hormones as perturbants in such systems.…”