Dissociation constants of phenols in methanol--water mixtures

A preferential solvation model that relates solute properties with solvent composition in binary mixtures has been applied to the dissociation pKa values of a set of 28 substituted phenols in methanol-water mixtures. The parameters of the model allow estimation of the pKa value of each phenol for any methanol-water composition. Moreover, it is demonstrated that the pKa values of the whole set of phenols at any methanol-water composition are linearly related to the pKa values of the phenols in water. Equations that relate the correlations' slope and intercept values with the solvent composition have been derived and tested with the set of phenols. The general parameters obtained for these equations allow an accurate calculation of the pKa value of any phenol, even of those not included in the original set, at any methanol-water composition solely from the pKa value of the phenol in water. These calculated pKa values can be used for quantitative structure-HPLC retention relationships. The method is tested by comparison of the calculated pKa values with the HPLC determined pKa values of 26 phenols in a polymeric column with a 50% methanol as mobile phase.     

Ligand exchange reactions of ferrocene with phenanthrene or 9,10-dimethylphenanthrene in the presence of aluminum chloride and aluminum

Ligand exchange reactions between phenanthrene or 9,10-dimethylphenanthrene with ferrocene effected in the presence of AlCl₃-Al were carried out under a variety of conditions. With phenanthrene (I), hydrogenation at the C-9 and C-10 positions could take place during the reaction and the cationic products obtained were the η⁶-phenanthrene-η⁵-cyclopentadienyliron and η⁶-9,10-dihydro-phenanthrene-η⁵-cyclopentadienyliron moncations (II and III), and the η⁶-phenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron and η⁶-9,10-dihydrophenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dications (IV and V). With 9,10-dimethylphenanthrene (VI), reactions carried out in refluxing cyclohexane gave the non-hydrogenated η⁶-9,10-dimethylphenanthrene-η⁵-cyclopentadienyliron monocation (VII) and η⁶-9,10-dimethylphenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dication (VIII). When higher temperatures were used in an attempt to promote hydrogenation, decomposition predominated and no cationic product could be obtained. These finding are discussed and contrasted with previous results obtained from similar reactions using anthracene or 9,10-dimethylanthracene.     

519—Reduction of hydrophobic porphyrin at the octane/water interface controlled by the specific adsorption of halogen anions

The redox reaction between the ferric complex of hydrophobic porphyrin and sodium dithionite in two different phases occurring at the interface between two immiscible liquids has been investigated by Volta potential measurements and spectroscopy. The reduction of the ferric complex of hydrophobic porphyrin adsorbed at the interface was found to be accompanied by a potential shift in the negative direction and to depend significantly on the nature of the anion and the ionic strength of the supporting electrolyte. Specifically adsorbed halogen anions inhibited the redox reaction in the sequence: Cl^?, Br^?, I^?. Depending on pH, the ferric complex of hydrophobic porphyrin exists in the uncharged (FeP-O-PFe) form or in the cation FeP⁺ form. The interaction between the ferric complex hydrophobic porphyrin and water has also been investigated.     

Reproducibility of glass open tubular columns in a production environment — Two years of experience

Summary The problems associated with the preparation of glass open tubular (capillary) columns are well documented in the literature. These problems are even more evident if column production is done on a routine basis, in a production environment. On the other hand, from the point of the user who wants to rely on a supplier, the reproducible quality of the columns is crucial. Here quality does not only mean efficiency but also refers to the reproducibility of the average liquid film thickness (capacity ratio) and the relative retention, as well as the tube treatment influencing the polarity of the column tube. In a paper published one year ago [1] our investigation concerning the reproducibility of the column manufacturing process was reported. The present paper continues this investigation. Four different columns will be considered: two types of OV-101 columns with thin and thick liquid film as well as columns prepared with Carbowax 20M and DEGS liquid phases. The consistency of their characteristics and efficiency will be investigated. Column characteristics include the capacity ratio which is directly related to the thickness of the liquid phase film. Column efficiency is investigated with help of the HETP and peak resolution. The effective and theoretical plate numbers are compared and the incorrectness of the assumption that the former is better suited for column testing is demonstrated. Relative retention reproducibility of even difficult peak pairs shows the consistency of column wall treatment. Finally, the consistency and performance of shorter columns obtained by the breaking of long columns will be discussed.Paper presented at the Second International Symposium on Glass Capillary Chromatography, Hindelang, Allgäu, Federal Republic of Germany, May 2–6, 1977.     

1,2,4-Triazine and triazole derivatives from α-keto acids and thiosemicarbazides

Thiosemicarbazides of 2-hydroxyphenylglyoxylic acid, which, depending on the conditions, undergo cyclization to interconvertible 5-(2-hydroxyphenyl)-6-oxo-1,2,4-triazine-3-thiones or (2-hydroxy-benzoyl)-²-1,2,4-triazoline-5-thiones, are formed by the action of thiosemicarbazide and its homologs on coumarindione. The thiosemicarbazones of 2-hydroxyphenylglyoxlyic and other 2-substituted phenylglyoxylic acids undergo cyclization to 6-(2-hydroxyphenyl)-5-oxo-1,2,4-triazine-3-thiones.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp, 116–121, January, 1977.     

Lifetimes of Hg(3P0) complexes with methanol,ammonia, and water

Lifetimes of Hg(³P₀) complexes were determined by simultaneous observation of Hg(³P₀) optical absorption and complex emission, using a modulation technique and phase sensitive detection. The lifetimes of the mercury complexes with methanol, (1.4 ± 0.7) × 10^-8 s, and water, ? 8 × 10^-8 s, were found to be much shorter than reported in earlier work. For the ammonia complex, however a lifetime was measured which is in good agreement with previous determinations. Reasons for the large errors in earlier work where the methanol and water complex lifetimes were determined from complex emission data alone are discussed, and these data are reinterpreted. In the reaction rate of Hg(³P₀) with methanol no detectable contribution from the termolecular process Hg(³P₀) + 2CH₃OH → (Hg·CH₃OH)^* + CH₃OH could be observed.     

Transformations of substituted tetrahydro-8h-indeno[1,2-d]imidazoles in concentrated sulfuric acid

The five-membered ring of the indene system in 2,8-dioxo-3a-hydroxy-8a-R-1,2,3a,8a-tetrahydro-8H-indeno[1,2-d]imidazoles is hydrolytically cleaved in concentrated sulfuric acid solutions. Depending on the reaction conditions, compounds for which substituted 4-(o-carboxyphenyl)imidazol-2-one (II), 1,8-dioxo-1,2-dihydro-8H-imidazo[4,3-a]isoindole (III), and spiro[imidazolidine-4,3′-phthalide] structures were assumed were isolated.     

Chelate mit Diimin- und Thiol-Struktur: Analytische Anwendung der Di-(4-substituierten)-thiosemicarbazone von 1,2- und 1,3-Diketonen

Zusammenfassung In der Gruppe der vierzähnigen Liganden mit Diimin- und Thiolstruktur bilden die Bisthiosemicarbazone von 1,2- und 1,3-Diketonen mit 4-substituierten Thiosemicarbaziden intensiv gefärbte Metallchelate, die für extraktionsphotometrische Bestimmungen in der Spurenanalyse verwendet werden können. Die molaren Extinktionskoeffizienten liegen im Bereich 5000–16000. Die leichte Zugänglichkeit von 4-substituierten Thiosemicarbaziden über die Reaktion von Isothiocyanaten mit Hydrazin bietet eine große Auswahl von Reagentien, besonders für die Flüssig-Chromatographie zur Trennung von komplexen Chelatgemischen.Die Arbeit wurde aus den Mitteln der Deutschen Forschungsgemeinschaft Bonn-Bad Godesberg gefördert.     

Fluoroalkyl-s-triazines

A series of symmetrically and asymmetrically substituted s-triazines was synthesized by condensation of fluorocarbon nitriles (Scheme II, compounds 1a-c ) and by cyclodehydration of a fluorocarbon imidoylamidine utilizing a fluorocarbon anhydride (Scheme III, compounds 2a-e ). Among the new nitriles prepared for incorporation in these reaction paths were 11-H-4,9-dioxahexadecylfluoroundecanenitrile ( 3 ) and 6-chloro-6-H-4-oxaheptafluorohexanenitrile ( 4 ), prepared by Scheme 1.     

Methods and Results of Optical Investigations on Semiconductor Interfaces

Measurement of the state of polarization of reflected light (ellipsometry) permits the determination of the thickness and refractive index of thin layers formed on a surface. The IR absorption spectra of such thin layers, which can be measured by means of internal reflection spectroscopy (IRS), provide information about their chemical composition. These methods have been used to study adsorption processes and the formation of reaction layers at semiconductor interfaces, and may also be used for measurements of free charge carriers in the space-charge region and in surface states. Results of such investigations are given in this article.