Quinoline-2-thiol Derivatives as Organic Reagents. I. Spectrophotometric Investigations on the Coloration with Some Metal Ions

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Twenty-nine derivative of quinoline-2-thiol were synthesized from thiourea and 2-bromo (or 2-chloro) quinoline derivatives. The limit of identification for metal ions with these reagents was examined by a spot test. These reagents gave a precipitate with the following metal ions : Cu⁺, Cu²⁺, Pd²⁺, Ag⁺, Pt⁴⁺, Au³⁺, Hg²⁺₂, Hg²⁺, and Bi³⁺. The effect of substituted groups on molecular extinction coefficient and wavelength of maximum absorption of reagents, of palladium (II) complexes, and of copper (I) complexes was studied. In these reagents, 4-phenyl-7-methoxyquinoline-2-thiol and 4-methyl-8-ethoxy-quinoline-2-thiol were the most sensitive reagents for palladium (II) and copper (I) in an acetic acid solution. Extraction of palladium (II) complexes with an immiscible organic solvent was also examined.