A common carbanion intermediate in the recombination and proton-catalysed disproportionation of the carboxyl radical anion, CO2*-, in aqueous solution

The carboxyl radical anion, CO2*- was produced by the reactions of OH radicals with either CO or formic acid in aqueous solution. The pKa(*CO2H) was determined by pulse radiolysis with conductometric detection at pH approximately equals 2.3. The bimolecular decay rate constant of CO2*- (2k approximately equals 1.4 x 10(9) dm3mol(-1)s(-1)) was found to be independent of pH in the range 3-8 at constant ionic strength. The yields of the products of the bimolecular decay of the carboxyl radicals, CO2 and the oxalate anion were found to depend strongly on the pH of the solution with an inflection point at pH 3.8. This pH dependence is explained by assuming a head-to-tail recombination of the CO2*- radicals followed by either rearrangement to oxalate or a protonation of the adduct, which subsequently leads to the formation of CO2 and formate. The recombination of CO2*- to give oxalate directly is estimated to have a contribution of <25%.     

Transition from a Bloch-Wilson to a free-electron density of states in Zn(n)- clusters

We present photoelectron spectroscopy studies on Zn(n) (-) in the size range of n=3-117. We show that zinc clusters exhibit a distinct transition in their electronic structure as a function of size. At small sizes (up to n=18) the clusters follow the Bloch-Wilson picture of the development of a metal from closed-shell atoms, exhibiting a gradual decrease of the gap between the fully occupied s band and the empty p band. For large sizes (n approximately or > 32) the band overlap allows the valence electrons to fully delocalize. This leads to an almost perfect free-electron density of states, as is demonstrated by discussing the spectra in the light of standard free-electron models and by comparison to the results obtained on sodium clusters.     

Quantitative analysis of perchlorate in extracts of whole fish homogenates by ion chromatography: comparison of suppressed conductivity detection and electrospray ionization mass spectrometry

The perchlorate anion (ClO ₄ ^– ) is an anthropogenic contaminant of increasing concern in water supplies, and has been shown to disrupt thyroid activity. Most perchlorate analyses are currently carried out by ion chromatography (IC) with suppressed conductivity detection (SCD). While this procedure has been demonstrated to provide acceptable performance for analysis of water samples, the determination of perchlorate in high-conductivity aqueous extracts of plant or animal material is not readily accomplished by IC-SCD unless lengthy cleanup protocols are applied. With the addition of electrospray ionization mass spectrometry (ESI-MS) to IC, it was hypothesized that the interference imposed by various ionic species could be significantly reduced without the need for purification; however, the analysis of perchlorate in relatively unpurified extracts of biologically derived homogenates by IC-ESI-MS has not previously been described in the literature. The research presented here represents a comparison of the capabilities of IC-SCD and IC-ESI-MS to detect perchlorate in reagent water and in crude extracts of perchlorate-exposed fish (threespine stickleback, Gasterosteus aculeatus). ESI-MS was found to compare favorably to SCD for the detection of perchlorate in deionized water, and to exceed SCD performance in perchlorate analysis of fish-derived extracts.     

Dioxomolybdenum(VI) complexes of 2-hydroxybenzaldehyde 4-phenyl-S-methylthiosemicarbazone

Mixed ligand complexes of dioxomolybdenum(VI) with 2-hydroxybenzaldehyde 4-phenyl-S-methylthiosemicarbazone (H₂L) were prepared with the formula [MoO₂(L)D] (D = H₂O, methyl, n-butyl, and n-undecyl alcohol, DMF, DMSO, pyridine, 4-picoline, and 3,5-lutidine). The compounds were characterized by elemental analysis, IR and ¹H NMR spectroscopy. The thermal decomposition of the compounds were investigated by using TGA, DTG, and DTA methods in air, and the thermal behavior depending on the second ligand molecule was discussed. A single crystal of the DMF coordinated complex was studied by X-ray diffractometry. The text was submitted by the authors in English.     

Determination of isoniazid, acetylisoniazid, acetylhydrazine and diacetylhydrazine in biological fluids by high-performance liquid chromatography

A high-performance liquid chromatographic assay for the determination of isoniazid, acetylisoniazid, acetylhydrazine and diacetylhydrazine (plasma and urine) was developed. The m-chlorobenzoyl derivatives of isoniazid, acetylhydrazine and the internal standard propionylhydrazine were prepared, separated on a RP-18 column and detected at 220 nm. Acetylisoniazid, diacetylhydrazine and the internal standard dipropionylhydrazine were converted to isoniazid, acetylhydrazine, and propionylhydrazine by acidic hydrolysis and subsequently derivatized with m-fluorobenzoyl chloride, separated on a RP-18 column and detected at 220 nm. The lower limits of detection in plasma are acetylhydrazine 0.5 nmol/ml, isoniazid 1.0 nmol/ml, diacetylhydrazine 1.0 nmol/ml and acetylisoniazid 2.0 nmol/ml, and in urine, acetylhydrazine 10 nmol/ml, isoniazid 15 nmol/ml, diacetylhydrazine 20 nmol/ml and acetylisoniazid 40 nmol/ml. This method is sensitive, reproducible, accurate and precise; therefore, it is well suited for detailed pharmacokinetic studies.     

2,6-dicyano-1,5-dimethylsemibullvalene as a probe for homoaromatic molecules of the Dewar-Hoffman type

The 2,6-dicyano-1,5-dimethylsemibullvalene (2d) synthesized via the bicyclo[3.3.0]octanedione 7 exists as a classical ground state which is lower in energy by less than 5 kcal/mole than the homoaromatic transition of the Cope rearrangement of 2d.     

Crystal structure and spectroscopic characterization of K8(VO)2O(SO4)6

Red and yellow dichroistic crystals of a vanadium(V) compound, potassium (mu-oxo, di-mu-sulfato)bis(oxodisulfatovanadate), K(8)(VO)(2)O(SO(4))(6), have been obtained from the ternary catalytic model melt system K(2)S(2)O(7)[bond]K(2)SO(4)[bond]V(2)O(5). By slow cooling of the melt from 420 to 355 degrees C, crystal growth occurred, using solid V(2)O(5) crystals present in the melt as nucleation promoter. The compound crystallizes in the monoclinic space group P2(l) with a = 13.60(9) A, b = 13.93(9) A, c = 14.05(9) A, beta = 90.286(10) degrees, and Z = 2. It contains two VO(6) octahedra linked together by a mu-oxo and two mu-sulfato bridges. Furthermore, each octahedron has two monodentate sulfate ligands, making the dimeric entity coordinatively saturated. IR spectroscopy shows bands arising from V[bond]O[bond]V and V[double bond]O stretches as well as splitting of sulfate bands due to the different degrees of freedom present for different conformations of sulfate ligands. The coordination of vanadium in K(8)(VO)(2)O(SO(4))(6) is discussed in relation to the reaction mechanism of SO(2) oxidation catalysis.     

Arbeiten über Phosphorsäure und Thiophosphorsäureester mit einem heterocyclischen Substituenten 9. Mitteilung 1. Aza-Analogie I: Aza-Analoge von Phthalimid-, Benztriazol- und 1,2,3-Benztriazin-4(3H)-on-Derivaten

Aza-analogues of the known pesticidal dithiophosphates 2, 4 and 5 have been prepared by replacing the phthalimide, benzotriazole and 1,2,3-benzotriazin-4(3H)-one moieties resp. in 2 by those of quinolinic acid imide (6), cinchomeronic acid imide (7) and pyrazine-2,3-dicarboxylic acid imide (12), in 4 by 1H-v-triazolo[4,5-b]pyridine (15) and in 5 by pyrido[2,3-e]1,2,3-triazin-4(3H)-one (21). Compared to the known compounds the new esters are less or at best equally pesticidal with an equal or even higher mammalian toxicity.     

Konzentrationsabhängigkeit der Dipolmomente in n-Hexan-Lösungen normaler α, ω-dichlorierter Kohlenwasserstoffe

Zusammenfassung Es wurden die Dipolmomente der, -dichlorierten Kohlenwasserstoffe in Lösung mit Hexan über den ganzen Konzentrationsbereich bei 25 °C bestimmt. Untersucht wurden die Verbindungen dieser Reihe vom 1,2-Dichloräthan bis zum 1,10-Dichlordekan.Die Dipolmomente dieser Verbindungen ließen sich gut deuten, wenn ein Gemisch starrer Rotationsisomerer angenommen wurde. Dabei zeigten sich auch noch die durch eine Kohlenstoffkette von 10 C-Atomen getrennten Partialmomente deutlich in ihrer Richtung gegenseitig abhängig.Die Konzentrationsabhängigkeit der Dipolmomente wurde an Hand der durch dieKirkwood-Fröhlichsche Theorie gegebeneng-Faktoren diskutiert. Es ergab sich, daß dieg-Faktoren des 1,2-Dichloräthans weitgehend auf eine DK-abhängige Konformationsänderung von der unpolaren trans- in die polare gauche-Konformation zurückzuführen sind. Dies scheint eine grundsätzliche Eigenschaft von Verbindungen zu sein, die Partialmomente in 1,2-Stellung haben. Dieg-Faktoren der Verbindungen, deren Partialmomente weiter voneinander entfernt sind, wie bei den höheren Gliedern der Reihe, wurden nahezu ausschließlich auf zwischenmolekulare Ausrichtung der Partialmomente zurückgeführt.Ein Vergleich mit deng-Faktoren des Hexylchlorids und des 2,2-Dichlorpropans zeigte, daß bis zu einer Konzentration von 1 Mol/l in erster Linie dimere bzw. kettenartige antiparallele bzw. parallele Assoziate der Partialmomente zu erwarten sind. Nach höheren Konzentrationen weichen dieg-Faktoren von diesem Verhalten nach größeren Werten hin ab. Daraus wurde auf parallele Ausrichtung in höherer Koordinationszahl geschlossen.Für die Unterstützung dieser Arbeit sprechen wir der Deutschen Forschungsgemeinschaft unseren verbindlichsten Dank aus.Der Firma Bayer, Leverkusen, danken wir für die Hilfe bei Beschaffung einiger der Substanzen.