Novel [1,5] sigmatropic rearrangements of cyclohexadienones generated from Fischer carbene complexes. A new strategy for installing the C-20 angular ethyl group in Aspidospermidine alkaloids

[formula: see text] We report here the first examples of a [1,5] sigmatropic rearrangement in a 4a-alkyl-4a-hydrocarbazol-4-one to yield a 3-alkylcarbazol-4-one with a re-aromatized indole nucleus. The reaction of 1-methyl-3-substituted-indole-2-carbene complexes 1 with terminal alkynes yields 3,4a-dialkyl-1-methoxy-9-methylcarbazol-4-ones 2. These 4a-substituted carbazolones thermally rearrange to cleanly give the more highly aromatic 3,3-dialkyl-1-methoxy-9-methylcarbazol-4-ones 3. This reaction provides a convenient entry to the Aspidosperma family of alkaloids, which contain a 3,3-disubstituted carbazole nucleus.     

Multivariate data analysis for x-ray fluorescence spectrometry

A multivariate data analysis procedure that uses singular value decomposition and the Ho-Kashyap algorithm is proposed to obtain calibration constants for x-ray fluorescence spectrometry. These calibration constants can be used to obtain results from experimental data by means of a simple dot product calculation. The method was tested on experimental data from the literature. Comparison of results showed that the method performs at least as well or better than the Rasberry-Heinrich method or its modifications. The method can be used to express calibration results obtained with a theoretically based program in such a way that they can be used conveniently in routine applications.     

Photochemical (2+2)-cycloaddition of thioxanthenethione with some butatriene derivatives

Irradiation of thioxanthenethione $\text{1}$ with the alkyl- and alkoxysubstituted butatrienes $\text{2}$a-d gives the thietanes $\text{3}$a-d the cyclobutanethione $\text{6}$ is formed as a byproduct. Free radical addition of iC₃H₇SH to $\text{2}$a predominantly occurs via terminal attack of the thiyl radical on the π-system.     

Infrared determination of unsaturated bonds in polyethylene

Summary A method is presented for the determination of the degree of unsaturation of polyethylene samples by means of infrared spectroscopy. The required extinction coefficients for the vinyl, vinylidene and transvinylene absorption bands, at 910, 885 and 963 cm^–1 resp. are determined on films prepared from mixtures of suitable unsaturated hydrocarbons with n-hexatriacontane or polyethylene. The degree of unsaturation found is in perfect agreement with ICl-titration data.

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Zusammenfassung Eine Methode zur Bestimmung des Grades der Ungesättigtheit von Polyäthylenproben durch IR-Spektroskopie wird vorgeschlagen. Die gesuchten Extinktionskoeffizienten für die Vinyl-, Vinyliden- und trans- Vinylen-Absorptionsbanden bei 910, 885, und 963 cm^–1 werden auf Filmen bestimmt, die aus Gemischen entsprechender ungesättigter Kohlenwasserstoffe mit n-Hexatriacontan oder Polyäthylen hergestellt werden.Der gefundene Grad der Ungesättigtheit stand in bester Übereinstimmung mit den nach der JCl-Methode gefundenen Werten.

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A preliminary publication on this subject has appeared in Polymer Letters 2, 339 (1964).     

Modelling of the migration effect occurring at an ISFET-based coulometric sensor-actuator system

The migration effect, in addition to diffusion, occurring at an ion-selective field-effect transistor (ISFET)-based coulometric sensor-actuator system has been studied. A diffusion-migration model is presented, based on the numerical solution of the Nernst-Planck equations of which a digital simulation is realized. Corresponding experiments were carried out and compared with the simulation. The results are in good agreement with the simulation.Typical titration times of this system were found to be 0.5–10 s, corresponding to fully dissociated acid concentrations of 0.5×10^?3?6.5×10^?3 mol 1^?1 with excess of supporting electrolyte. Both the simulation and experimental results show that if the concentration of the supporting electrolyte is ? 20 times higher than that of the species to be titrated, the deviation caused by migration is less than 5% and within the experimental error when pure diffusion is considered. At relatively low concentrations of supporting electrolyte, the migration effect should be taken into account to determine the concentrations of titrated species.     

Volatile components from Anthriscus sylvestris (L.) Hoffm

The volatile components of fresh leaves and roots from Anthriscus sylvestris (L.) Hoffm., obtained through hydrodistillation, were analysed by GC and GC-MS. This was compared to dichloromethane extracts of both fresh and dried leaf and root material. The monoterpene fraction (69-70%) dominated, while beta-phellandrene (39-45%) was the main component in both the leaf and the root oil. Other components in the leaf oil were beta-myrcene (17%), sabinene (6.2%), Z-beta-ocimene (5.4%) and benzene acetaldehyde (4.1%). In the roots we found Z-beta-ocimene (16.9%) and alpha-pinene (4.6%) as other major components. These principle constituents of both essential oils were also present in the dichloromethane extracts of the fresh and dried leaves and the roots, although in much smaller percentages. Comparing hydrodistillation of fresh plant material with a dichloromethane extract, the latter yielded a considerably lower amount of constituents. In addition, air drying and freeze drying resulted in a significant loss of volatile constituents as compared to fresh material (dichloromethane extract).     

Isolation of a crystalline thiete and its ‘open’ isomer; Photoproducts of xanthenethione and bis(tert-butylthio)ethyne

Irradiation of xanthenethione $\text{1}$ with bis(tert-butylthio)ethyne $\text{2}$ yielded both the expected α,β-unsaturated dithioester $\text{4b}$ and surprisingly its proposed intermediate thiete $\text{3b}$ as crystalline compounds. In solution an equilibrium between both compounds has been observed.     

An online computer method for the potentiometric titration of mixtures of a strong and a weak acid

A PDP-11 online computer method for the titration of mixtures or a strong and a weak acid is described.The method is based on multiparametric curve-fitting. One or the parameters found from the calculations is the dissociation constant of the weak acid, hence the method can be applied even when this constant is unknown. Accurate results (relative error ±1%) were obtained for weak acids with pK_a values of 0.2–10. A complete titration and calculation takes about 20 min.