Identification of two aromatic isomers between 2- and 3-hydroxy benzoic acid by using a Briggs-Rauscher oscillator

A new technique for identification of two aromatic isomers between 2-hydroxy benzoic acid (2-HBA) and 3-hydroxy benzoic acid (3-HBA) was finalized by using their perturbation effects on a Briggs-Rauscher (BR) oscillator, in which a tetraazamacrocyclic Ni complex, [NiL](ClO 4 ) 2 was used as catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. By putting two isomers into this BR oscillator, the 2-HBA caused a decrease in potential (amplitudes), an increase in the period of oscillation (∆   T) and a decrease in number of the oscillation cycle (n) while no influences of 3-HBA on the BR oscillation were observed. Hence, these two aromatic isomers of hydroxy benzoic acid (HBA) were identified in the range from 1   ×   10 −   5 to 2.2   ×   10 −   4   mol   L −   1 . Reaction mechanism of BR has been proposed with reference to the NF and FCA models. An explanation of perturbation mechanism for the BR is that, only 2-HBA reacted with IO 2 • to form 1,2-quinone while the 3-HBA didn't.