Synthesis, Characterization and Hg(II) Ion Selectivity of 1-(2-Nitro-4-methyl phenyl)-6-methyl-6-methoxy-1,4,5,6-tetrahydro-pyrimidine-2-(3H) thione (TPT)

Abstract

1-(2-Nitro-4-methyl phenyl)-6-methyl-6-methoxy-1,4,5,6-tetrahydro-pyrimidine-2-(3H)thione (TPT) has been synthesized by the reaction of 4-isothiocyanato-butan-2-one with 4-methyl-2-nitroaniline at reflux temperature in methanol using a catalytic amount of sulfuric acid (pH ca. 3). The TPT product was characterized by 1H NMR, HRMS and IR. PVC-based membranes of TPT were prepared and investigated for response towards Hg2+ ions. Best performance was observed with the membrane containing 10, 200, and 200 mg of TPT, DOP (dioctylphthalate) and PVC, respectively. The membrane electrode works well over a wide concentration range 1.1×10–5–1.0×10–1 M of Hg2+ with a slope of 28.6 mV/decade of concentration of Hg2+. The useful pH range for the electrode was found to be 2.3–4.2 with a response time of 30 s. The selectivity coefficient values are of the order of 0.01 for mono-, bi-, and trivalent cations which indicate good selectivity for Hg2+ ions over a large number of cations. The electrode has a lifetime of 3 months and could also be used as an indicator electrode in the potentiometric titration of Hg2+ vs. EDTA.