J.L.Gómez Ariza

Derivatives of rhodanine as spectrophotometric analytical reagents: I. Condensation at C-5 with aromatic pyridine and nonpyridine aldehydes

Abstract The synthesis, characteristics, properties, and reactions with metallic ions of five aromatic (three nonpyridine and two pyridine) derivatives of rhodanine have been studied. Nonpyridine derivatives exhibit one pK value in aqueous solution and two pyridine reagents, and with Pd(II), Au(III), Hg(II), and Cu(I) and (II) form stable complexes which show an absorption band, at the visible zone of the spectrum, with molar absorptivities adequate for spectrophotometric measurements. Finally, suggestions have been made about the group responsibile for the reactionability.

Derivatives of carbohydrazide, thiocarbohydrazide and diaminoguanidine as photometric analytical reagents-I 1,3-bis[(2-pyridyl)methyleneamino]thiourea and 1,3-bis[(2-pyridyl)methyleneamino]guanidine.

1,3-Bis[(2-pyridyl)methyleneamino]thiourea (PMAT) and 1,3-bis[(2-pyridyl)methyleneamino]-guanidine (PMAG) have been prepared. They have been examined and characterized by infrared and ultraviolet spectroscopy. A spectrophotometric method has been used for determination of the protonation constants of the reagents. Finally, a spectrophotometric survey has been made of the reactions of various cations with PMAT and PMAG.

Picolinaldehyde 4-phenyl-3-thiosemicarbazone as a spectrophotometric reagent for the selective determination of small amounts of cobalt in the presence of iron.

The characteristics and analytical applications of picolinaldehyde 4-phenyl-3-thiosemicarbazone are described. This compound gives coloured reactions with cobalt(II), iron(II) and (III), nickel(II), copper(II), palladium(II) and other ions, that are much more sensitive than those with picolinaldehyde thiosemicarbazone. The 1:2 yellow cobalt(II) complex has been used for the spectrophotometric determination of cobalt in the presence of iron, and applied to steel analysis.

Derivatives of 2-thiohydantoin as spectrophotometric analytical reagents

The synthesis, characteristics, properties and reaction with metallic ions of four pyridine derivatives of 2-thiohydantoin have been studied. 5-(2-Pyridyl)methylene-2-thiohydantoin, 5-(6-methyl-2-pyridyl) methylene-2-thiohydantoin, 5-(di-2-pyridyl)methylene-2-thiohydantoin and 5-[1-(2-pyridyl)-1-methyl] methylene-2-thiohydantoin have been synthesized. The substances exhibit three pK values in aqueous solution and with Ag(I), Au(III), Cu(II), Pd(II) and Zn(II) form complexes with high molar absorptivities.

Solvent effects on the dissociation of bromopyridinium ions in N,N-dimethylformamide mixtures by electrochemical measurements

Abstract Thermodynamic proton dissociation constants of 2-, 3- and 4-bromopyridinium ions were evaluated by using potentiometric and polarographic techniques in 20–60% (v/v) N,N-dimethylformamide/water mixtures at 25 ± 0.1°C, applying an empirical pH correction for mixed aqueous solvents. Non-electrostatic factors exert a considerable influence on the dissociation of halopyridinium ions. The solvation numbers for these ions were determined by analysing the experimental data mathematically.

Nonpyridinic derivatives in C-5 of 2-thiohydantoin for spectrophotometric determination of palladium

Abstract The reactions between Pd(II) and four nonpyridinic derivatives of 2-thiohydantoin (5-benzal-2-thiohydantoin, 5-( o -hydroxy)benzal-2-thiohydantoin, 5-( m -hydroxy)benzal-2-thiohydantoin, and 5-anisal-2-thiohydantoin) have been considered. The influence of the different experimental parameters on the formation of the complexes was studied, and the optimum conditions for the determination of palladium were established. The anisal derivative was selected among these four reagents and the spectrophotometric determination of palladium described in detail. The precision of the procedure, expressed in terms of relative standard deviation was 0.9%, and numerous ions that usually interfere in palladium determination, such as Os(VIII), Rh(III), and Ru(IV) (of the platinum group) and Pb(II), Cd(II), Ni(II), Co(II), Zn(II), and others of the transition series, were tolerated.

The Spectrophotometric Determination of Nickel and Cobalt in Mixtures with Picolinaldehyde 4-Phenyl-3-Thiosemicarbazone

Abstract The properties of nickel complex of picolinaldehyde 4-pheny1-3-thiosanicarbazone are described. The optimal conditions for a selective and sensitive spectrophotometric determination of nickel are discussed, A photometric method for the determination of traces of cobalt(II) and nickel(II) ions in mixtures has also been developed.

Spectrophotometric determination of gallium in alloys and fly-ash with pyridoxal derivatives of thiocarbohydrazide and carbohydrazide

The symmetric derivatives of pyridoxal with thiocarbohydrazide and carbohydrazide, and the asymmetric derivatives of pyridoxal and salicylaldehyde with the same hydrazides have been synthesized and their analytical potential for spectrophotometric and kinetic fluorimetric determination of metal ions was studied. Gallium(III) and PyMAU(1,3-bis{[4-(2-methyl-3-hydroxy-5-hydroxymethyl)pyridyl]methyleneaminourea at pH = 4.2 form a complex with a single absorption maximum at 425 nm, which can be extracted into cyclohexanone in the presence of a controlled amount of sodium perchlorate. The extract has maximum absorbance at 435 nm. Both systems can be used for determining gallium. The optimal range of gallium concentration for measurement in a 1-cm cell is 0.5-1.25 gmg/ml for the procedure in homogeneous medium ((425) = 3.76 x 10(4).mole(-1).cm(-1)) and 0.25-1.25 mug/ml for the extraction procedure ((435) = 5.30 x 10(4) 1.mole(-1).cm(-1). The latter procedure has been applied to the determination of gallium in alloys and fly-ash.

1,5-Bis[di-(2-pyridyl)-methylene] derivatives of carbonic and carbonimidic dihydrazides as analytical spectrophotometric reagents. Spectral examination of reagents and study of metal reactionability

Abstract Bis[di-(2-pyridyl)-methylene]-carbonic dihydrazone (DPKCH), and bis[di-(2-pyridyl)-methylene]-carbonimidic dihydrazone (DPKIH) were prepared, examined, and characterized by ultraviolet and infrared spectroscopy. The spectrophotometric method was used for the determination of the stability constants of hydrogen complexes, and the reactionability of the reagents as well as their possible use in photometric analysis were studied and discussed.

Spectrophotometric determination of mercury with 5-(6-methyl-2-pyridyl)methylene-2-thiohydantoin

Abstract A method is described for the direct spectrophotometric determination of mercury(II) with 5-(6-methyl-2-pyridyl)methylene-2-thiohydantoin. The influence of the different experimental parameters on the formation of the complex were studied and optimum conditions for the determination of mercury were established. The precision of the procedure, expressed in terms of relative standard deviation, was 0.2%. Two different complexes (1:2 and 1:1 cation-reagent stoichiometries) have been detected. The method has been tested on copper amalgam for dental use.