The analysis of the zero-order and the second derivative spectra of retinol acetate, tocopherol acetate and coenzyme Q10 and estimation of their analytical usefulness for their simultaneous determination in synthetic mixtures and pharmaceuticals

The aim of the present work was to develop a simple and rapid method of retinol acetate, tocopherol acetate and coenzyme Q(10) determination in pharmaceuticals without involving any preparation operations like separation or masking. The values of second derivative amplitude at 212 nm for tocopherol, 351 nm for retinol and 222 nm for coenzyme were used for construction of calibration graphs. Beer's law is obeyed in the concentration range 0.5-20, 0.5-7.5 and 0.5-30 microg ml(-1) for retinol acetate, tocopherol acetate and coenzyme, respectively. The elaborated procedures were successfully applied to the simultaneous determination of studied compounds in their binary synthetic mixtures and in commercial preparations with high reliability and repeatability. Spectral properties of retinol acetate allows to determine its contents in ternary mixture which includes Vitamin E and coenzyme Q(10).     

Mechanism and control of molecular energy flow: a modeling perspective

 Vibrational energy flow in organic molecules occurs by a multiple-time-scale mechanism that can be modeled by a single exponential only in its initial stages. The mechanism is a consequence of the hierarchical structure of the vibrational Hamiltonian, which leads to diffusion of vibrational wavepackets on a manifold with far fewer than the 3N−6 dimensions of the full vibrational state space. The dynamics are controlled by a local density of states, which does not keep increasing with molecular size. In addition, the number of vibrational coordinates severely perturbed during chemical reaction is small, leading to preservation of the hierarchical structure at chemically interesting energies. This regularity opens up the possibility of controlling chemical reactions by controlling the vibrational energy flow. Computationally, laser control of intramolecular vibrational energy redistribution can be modeled by quantum-classical, or by purely quantum-mechanical models of the molecule and control field. Received: 26 July 2002 / Accepted: 30 September 2002 / Published online: 2 December 2002 Electronic Supplementary Material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00214-002-0394-2. Acknowledgements. This work was supported by NSF grant CHE 9986670. Correspondence to: M. Gruebele e-mail: gruebele@scs.uiuc.edu     

Evaluation of molecular structure in Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate by IR external reflection spectroscopy

 In situ polarized Fourier transform IR external reflection spectra of Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate on a water surface were recorded for various surface areas, and their molecular structures were estimated. In the zinc stearate monolayer, the wavenumbers and the absorbances of the antisymmetric and symmetric methylene stretching bands did not change during monolayer compression, which means that orientational and conformational changes of the hydrocarbon chain did not occur. However, wavenumber changes of the antisymmetric and symmetric carboxylate stretching bands were observed during surface compression. The change in the binding nature of the zinc cation to the carboxylate group was speculated. Moreover, it was elucidated that the structure of the hydrocarbon chain in the zinc 12-hydroxystearate monolayer was different from that in the zinc stearate monolayer. Received: 21 March 2001 Accepted: 6 July 2001     

Catalytic activity of silica in ozone formation in electrical discharges

The catalytic action of granular silica packing on ozone formation has been observed under discharge conditions. Using a glass ozonizer with a metal high-voltage electrode, at a frequency of 400 Hz it was possible to obtain much higher ozone concentrations in the presence q( silica than without packing, with the same total energy consumption. The dependence between ozone production and energy efficiency is considered, and conditions of the optimum ozonizer run are discussed. It is shown that in the all-glass ozonizer with a narrow discharge gap, the ozone concentration may be as high as 6.5% (ca. 130g O₃/m³) when silica packing is applied.     

Application of organolithium and related reagents in synthesis,Part XII. Synthesis of phenyl- and pyridylpyridopyridazinones and their derivatives

Summary The preparation of the pyridazinones10a,10b,11a,11b, and12a,12b from the ketoamides7,8, and9 and hydrazine hydrate is described. It was found that from ketoamides8b and9b in addition to the expected pyridopyridazinones11b and12b also aminopyridopyridazines14 and15 were formed and that ketoamide7b gave exclusively aminopyridopyridazine13. The pyridopyridazinones10b,11b, and12b were alkylated with alkyl iodides.

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Anwendungen von Organolithium und verwandten Reagenzien in organischen Synthesen, Teil XII. Synthese von Phenyl- und Pyridylpyridopyridazinonen und ihren Derivaten

Zusammenfassung Die Darstellung der Pyridazinone10a,10b,11a,11b und12a,12b aus Ketoamiden7,8 und9 und Hydrazinhydrat wird beschrieben. Es wurde festgestellt, daß aus Ketoamiden8b und9b außer den erwarteten Pyridopyridazinonen11b und12b auch Aminopyridopyridazine14 und15 enstanden und daß das Ketoamid7b ausschließlich ins Aminopyridopyridazin13 überführt wurde. Die Pyridopyridazinone10b,11b und12b wurden mit Alkyljodiden alkyliert.

     

Cyclic Conjugation Energy Effects in Polycyclic π-Electron Systems

Summary. The fact that cyclic arrangements of double bonds have a dramatic effect on the behavior of conjugated organic molecules is known since the 19th century. The fact that in monocyclic conjugated systems the size of the cycle and the number of -electrons involved is decisive for their stability (aromaticity) or lack of stability (antiaromaticity) is known since the 1930s. In polycyclic -electron systems several cyclic effects are present simultaneously and their separation became possible only recently. A molecular orbital method has been elaborated, by means of which the energy effects of individual cycles in polycyclic -electron systems can be estimated. This method is briefly outlined and illustrated by pertinent examples. An exhaustive bibliography of the topic considered is given.     

A kinetic method for <Emphasis Type="Italic">para</Emphasis>-nitrophenol determination based on its inhibitory effect on the catalatic reaction of catalase

The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction: in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10⁻⁵–2.5·10⁻⁵ mol/L and the detection limit was 3·10⁻⁶ mol/L (417 μg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, meta-and orto-nitrophenol were observed.     

Kinetics of thermal decomposition of Co3O4 powder and single crystals

Kinetics of thermal decomposition in vacuum of Co₃O₄ powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co₃O₄ proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)^2/3 = ktⁿ where the activation energy varies with the degree of decomposition.     

Gas-phase solvation of protonated aliphatic amines: methyl,ethyl, n-propyl,and iso-propylamine

The thermodynamic quantities K_{n?1 n}, ΔG⁰_{n?1, n} and ΔS⁰_n?1, n for the gas phase equilibrium reactions RNH⁺₃(RNH₂)_n?1 + RNH₂ = RNH⁺₃(RNH₂)_n, where n ? 3 and R indicates an alkyl group (CH₃, C₂H₅, n-C₃H₇ and iso-C₃H₇), have been determined.     

All-solid-state planar miniature ion-selective chloride electrode

All-solid-state ion-selective electrodes with plastic membrane (poly(vinyl chloride) (PVC), bis(2-ethylhexyl) sebacate (DOS), methyltri-n-tetradecylammonium chloride (MTTACl)), a conducting poly(pyrrole) (PPy) film doped either with chloride ions (PPyCl) or hexacyanoferrate(II) ions (PPyFeCN), and glassy carbon (GC) or screen-printed graphite layer (S-PG) as an inner electric contact were investigated. All the electrodes show close to Nernstian response, but their lifetimes vary. The at least 2-months lifetime of screen-printed electrodes is only achieved for the electrodes containing PPyFeCN (cation-exchanging film). Shorter lifetime of other screen-printed electrodes, i.e. without PPy, or with PPyCl (anion-exchanging film), was attributed to the diffusion of anionic products of the hydrolysis of organic components of the graphite paste used to prepare the electric contact. The properties of miniature, screen-printed electrodes comprising PPyFeCN solid contact, were comparable to those ion-selective electrodes with PPy solid contact (regardless the ion-exchanging characteristic of the polymer) deposited on GC electric contact.