Henry. Freiser

Infra-red absorption spectra of metal chelates derived from 8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline, and 4-methyl-8-hydroxyquinoline

The infra-red absorption spectra of solid 8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline, 4-methyl-8-hydroxyquinoline, and of a number of metal chelates derived from these reagents, have been studied. In general, the spectra of the metal chelates derived from a given reagent were found to be quite similar. Significant differences were, however, observed in several instances, which may be useful analytically. An absorption peak at about 9 μ was found in the spectra for the chelates of all three reagents. It is suggested that this peak is associated with C-O vibrations in these molecules. When the “9 μ” peak positions for divalent-metal 8-hydroxyquinolates are plotted against the atomic weights of the corresponding metals, the points for the transition-metal chelates fall near one straight line, while the points for the remaining metal chelates fall near another. It is suggested that this may indicate either involvement of 3d orbitals in metal-ligand bonding for the transition-metal 8-hydroxy-quinolates or, alternatively, a difference in crystal structure for the two classes of chelates.

Structure and behavior of organic analytical reagents : Heats and entropies of formation of several divalent metal chelates of 2- and 4-methyl-8-hydroxyquinoline1

Abstract The Calvin-Bjerrum titration technique for the determination of chelate formation constants has been applied to the Cu(II), Ni(II), Co(II), Zn(II) and Mn(II) chelates of 2- and 4-methyl-8-hydroxyquinoline. Measurements were made at several temperatures in order to evaluate Δ H and Δ S values of chelation. The results obtained were interpreted in terms of steric hindrance of the 2-methyl group. In all cases the heats of formation of the chelates of 2-methyl-8-hydroxyquinoline were remarkably morepositive than those for the corresponding chelates of 4-methyl-8-hydroxyquinoline. This large difference in the strengths of the metal-chelate bonds is apparently due to the hindrance of the methyl groups which prevent the close grouping of the two reagent molecules around the metal in chelates of 2-methyl-8-hydroxyquinoline. The lower bond strength in chelates of 2-methyl-8-hydroxy-quinoline is partially compensated by a relatively larger entropy of formation. This is attributed to decreased solvent chelate interaction caused by the shielding of the polar O, N, and metal atoms by the 2-methyl groups. The determination of chelate fortmation constants of 2-phenyl-8-hydroxyqumoline has been carried out to further extend our study of steric effects in metal chelates.

Structure and behavior of organic analytical reagents : Dimethylglyoxime and its oxygen monomethyl ether

Abstract The titration procedure described in previous papers of this series has been applied to a study of some metallic chelates of dimethylglyoxime and of its O-monomethyl ether. Evidence is presented for the existence of dimethylglyoxime chelates with Zn (II), Pb (II), Cd (II), and La (III) in addition to the known Cu (II), Ni (II), and Co (II) complexes. Formation constants are calculated for these complexes, and for those of dimethylglyoxime O-monomethyl ether, on the basis of their most probable structures. The results indicate that the famed specificity of dimethylglyoxime fur nickel does not lie in any special stability of this chclate. but in some other factor, possibly solubility. A comparison of the chelates of dimethylglyoxime with those of its O-ether is discussed in terms of such structural factors as hydrogen bonding and steric hindrance. Heat content and entropy changes have been calculated for the chelation of dimethylglyoxime with Cu (II) and Ni (II) ions.

Structure and behavior of organic analytical reagents

Abstract The reactions of the chelating reagents named in the title, with a number of metal ions, have been studied in order to evaluate the behavior of reagents containing reactive groupings analogous to those of 8-hydroxyquinoline, but so arranged as to form six-membered ring chelates with metal ions. All three reagents have been found to give less stable chelates than 8-hydroxyquinoline, indicating that for this type of reagent, six-membered ring chelates are less stable than five. 2-( o -Hydroxy-phenyl)-benzoxazole and 2-( o -hydroxyphenyl)-benzothiazole have been found to be potentially useful as organic precipitating agents for metal ions, being more selective than 8-hydroxyquinoline, which they somewhat resemble in behavior. In contrast to the oxazole and thiazole, 2-( o -hydroxyphenyl)-benzothiazoline was found to react with most of the metal ions tried. Because of the solubility of its chelates in organic solvents, 2-( o -hydroxyphenyl)-benzothiazoline may be a useful solvent extraction agent for metal ions.

Structure and behavior of organic analytical reagents : Stability of chelates of 2-(o-hydroxyphenyl)-benzimidazole and analogous reagents1

Abstract Stabilities of chelates of 2-( o -hydroxyphenyl)-pyridine, 2-( o -hydroxyphenyl)-quinoline, 1-( o -hydroxyphenyl)- iso quinoline, 2-( o -hydroxyphenyl)-benzimidazole, and 2-( o -hydroxyphenyl)-imidazoline were determined by the Calvin-Bjerrum potentiometric titration technique. The results have been interpreted in terms of steric considerations.

Use of butyl phosphate in steel analyses : Determination of aluminum

Abstract The analysis of steel is simplified in a large measure by the removal of iron prior to the determination of a number of constituents. This report deals with the extraction of iron as the thiocyanate complex with n-butyl phosphate. The condition for optimal iron extraction were investigated. It was found that at a thiocyanate to iron ratio of 6 : 1, removal of iron by the ester is 97.5 % using one extraction. This technique was successfully applied to the determination of aluminum in steel.

APPLICATIONS OF THE GAUSSIAN ERROR FUNCTION IN ANALYTICAL CHEMISTRY

163. Using QuattroPro to examine the properties and fundamental statistical parameters of Gaussian error curves.

Polarography of 4-benzothiazolol

Abstract The polarographic behaviour of 4-benzothiazolol at the dropping mercury electrode has been compared with that of 8-quinolinol. A well-defined, irreversible cathodic wave, suitable for the determination of 4-benzothiazolol, was obtained at PH 6.8. The characteristics of this wave indicated that it was due to a two-electron reduction of 4-benzothiazolol to 2,3-dihydro-4-benzothiazolol.