Synthesis of a new heterocyclic dye compound as an indicator in acid and base reactions

 

Khorsandi Chenarboo, Mahdi ; Ebrahimi, Mahmoud ; Pordel, Mehdi ; Razmi, Mina

Abstract

In the present research, the use of 2-(3-hydroxyamino-2,3-dihydroimidazo[1,2-a]pyridine-2-ylidene)-2-(2-tienyl)acetonitrile as a new acid and base indicator in aquatic environments has been investigated. This compound has been synthesized by the reaction of 3-nitroimidazo [1,2-a] pyridine and 2-(2-thienyl) acetonitrile in a methanol solution by the hydrogen nucleophilic substitution. The aqueous-ethanol solution of this compound shows a change in color by adding acid and an base. For the potential function of this reagent as an indicator, the spectral properties of UV-Vis and the equilibrium of acid and base source have been examined. The results show that the reagent is an amphoteric with two stable ionization factors Ka and Kb with poor acid and base properties. Indicator dissociation constants in aqueous solutions specified by spectrophotometric method are pKa = 9.73 and pKb = 11.57. The types of base that can be titrated with this index have been reported. This index has been compared with effective acid and base indexes with similar pH range.

 


Keyword(s)

3-Nitroimidazo [1,2-a] pyridine, nucleophilic substitution of hydrogen, indicator, spectroscopy

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