Flash photolysis resonance fluorescence investigation of the reactions of OH radicals with OCS and CS2

Rate constants for the reaction of OH radicals with OCS and CS₂ have been determined at 296 K using the flash photolysis resonance fluorescence technique. The values derived from this study are k_{OH + OCS} = (5.66 ± 1.21) × 10^?14 cm³ molecule^?1 s^?1 and k_{OH + CS2} = (1.85 ± 0.34) × 10^?13 cm³ molecule^?1 s^?1, where the uncertainties are 95% confidence limits making allowance for possible systematic errors.     

Vibrational population distribution of ground state BaO formed by the reaction Ba + O2

The vibrational population distribution of X ¹Σ(υ′' = 0 through ν′' = 7) BaO formed in the reaction Ba + O₂ at 0.3 torr has been measured by laser induced photoluminescence intensities. On the basis of the assumed similarity between the Ba + O₂ and Ba + N₂O reactions, these data suggest that a population inversion may exist between A ¹Σ(ν′ = 1) and X ¹Σ(υⁿ = 7) BaO formed in the latter reaction at ≈ 16 torr.     

Flash photolysis resonance fluorescence study of the reaction Cl + O3 → ClO + O2 over the temperature range 213–298 K

Rate constants for the removal of Cl atoms in the reaction Cl + O₃ → ClO + O₂ were measured by the flash photolysis resonance fluorescence technique over the temperature range 213–298 K. The rate constant is given by the Arrhenius expression (2.94 ± 0.49) × 10^?11 exp[?(298 ± 39)/T] in units of cm³ molecule^?1 s^?1. Comparison with recent results from other laboratories are presented.     

Porphyrins

The extended Hückel model is applied to porphyrin systems with metals Mn, Fe, Co, Ni, Cu, Zn and to the diprotic acid. A single method for choosing parameters is detailed. The model is used to discuss magnetic state, coupling of ring and metal, electronic transitions, and the effect of non-planarity.

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Zusammenfassung Die erweiterte Hückel Theorie wird auf das Porphyrin-System mit den Metallen. Mn, Fe, Co, Ni, Cu und Zn sowie auf die zweifach protonierte Säure angewendet. Die Parameter werden dabei einheitlich gewählt. Anhand dieses Modells werden magnetische Eigenschaften, Kopplung zwischen Ring und Metall, Elektronenübergänge und der Einfluß der Abweichung von planarer Anordnung diskutiert.

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Résumé Le modèle étendu de Hückel est appliqué aux complexes du porphyrine avec les métaux Mn, Fe, Co, Ni, Cu et Zn, et à l'acide diprotonique. On présente en détail une méthode unifiée pour obtenir les paramètres. L'état magnétique, le couplage cycle-métal, les transitions électroniques et l'effet de la non-planeïté sont discutés à l'aide de ce modèle.

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National Institutes of Health Pre-Doctoral Fellow.     

Synthesen in der Carotinoid-Reihe. 22. Mitteilung. Totalsynthese von Rhodoxanthin

The total synthesis of rhodoxanthin according to the scheme C₁₄ + C₁₂ + C₁₄ is reported.     

Size-selective organization of enthalpic compatibilized nanocrystals in ternary block copolymer/particle mixtures

Dependent on the relative particle core size, two distinct types of particle topologies in block copolymer/nanocrystal blends have been identified, that is, the localization of particles along the intermaterial dividing surface or at the center of the respective polymer domain. In ternary systems consisting of block copolymer and two different-sized nanocrystal species, the distinct morphological types are conserved, resulting in autonomous size-selective separation and organization of the respective nanocrystals within alternating arrays and sheets.     

Diiodine complex of diferrocenyl(phenyl)phosphine sulfide: the structural and electrochemical behaviour of Fc2(Ph)PS · I2

The title compound, Fc₂(Ph)PS · I₂, has been prepared and characterised in both the solid state and solution. Single crystal X-ray crystallography reveals that the adduct adopts a molecular charge-transfer structure in the solid state. Mössbauer spectroscopy confirms the presence of low spin Fe²⁺ but also indicates the presence of ca. 24% of an Fe³⁺ species. The electrochemistry of Fc₂(Ph)PS · I₂, Fc₂(Ph)PS and Fc₂(Ph)P has been studied using a combination of cyclic voltammetry and differential pulse voltammetry. The data for Fc₂(Ph)PS · I₂ show two redox processes, consistent with the sequential oxidation of the ferrocenyl groups to ferrocenium species.     

Multi-residue method for rapid screening and confirmation of pesticides in crude extracts of fruits and vegetables using isocratic liquid chromatography with electrospray tandem mass spectrometry

A LC-MS-MS method capable of the quantitative determination of a range of pesticide residues present in crude extracts from a variety of fruit and vegetables has been developed. Isocratic LC conditions have been used in conjunction with electrospray ionisation tandem mass spectrometry to detect and identify up to 38 pesticides presented as various mixtures in different matrices. The utility of the method is demonstrated by the analysis of crude extracts, with no sample clean up, from grape, kiwi fruit, strawberry, spinach, lemon, peach and nectarine. Mean recoveries ranging from 63 to 96% with relative standard deviations < 20% were obtained for 30 of the 38 pesticides following analysis of organic produce fortified at concentrations between 0.01 and 0.8 mg/kg. Detected residues were quantified from interpolation against calibration data generated using matrix-matched standards that covered analyte concentration ranges between 0.005 and 0.8 microg/ml. Conditions suitable for the qualitative and quantitative confirmation of residues detected in samples are specified.