Identification of Two Hetero-Substituent-Aromatic Isomers of - 4- and 7-Hydroxy Coumarin with the Belousov-Zhabotinsky Oscillator

In this article, we presented an innovative work of distinguishing the two different positional heterosubstituents-aromatic isomers i.e. 4-hydroxycoumarin (4-HC) and 7-hydroxycoumarin (7-HC) on their perturbation effect by a novel analytical Belousov-Zhabotinskii (BZ) oscillator. In such BZ oscillator, the tetra-aza-macrocyclic copper complex ([CuL](ClO4)2) was used in which the ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraeazacyclotetradeca-4,11 diene. Experimental data confirmed that, by discrete injection of these two isomers (4-HC and 7-HC) into the active BZ system with equal concentrations reflected in their inhibition time (t in ), but the tin produced by 4-HC was higher than the tin initiated by 7-HC. The interesting feature is that, with increasing concentrations (9.0 x 10 -5 to 3.6 x 10 4 ) of 4-HC constantly increase the tin and decreased the oscillation number (N) after the regeneration of oscillation. Whereas, the upsurge concentrations of 7-HC didn’t change the tin but reduced the N after regeneration of oscillation. Thus, the two isomers were identified. Based on the mechanistic approach of FKN (Field-Koros-Noyes) model, the reaction perturbation mechanism was discussed. A fleeting description is that both 4-HC and 7-HC isomers were oxidized by BrO 2 intermediate radical (which produce during the course of reaction) into salicylic acid and quinone respectively and the system was temporary freeze (t in ) as well. The products (salicylic acid and quinone) were identified by infra-red and Ultra-Visible spectroscopies.