Über eine neue Synthese von Desmethylambraoxid

A new synthesis of the title compound starting from abietic acid is described. Regioselective osmylation of the ^{13, 14}-double bond of abietic acid methyl ester (6) and subsequent hydrogenation furnishes dihydrodihydroxyabietic acid methyl ester (12) with anall-trans-connection of the three rings. Periodate cleavage of12 leads to13 which can be transformed into the triester14 byBaeyer-Villiger oxidation. The configuration of the aldehyde group in13 as well of the formyloxy group in14 has been ensured to be equatorial.LAH-reduction of14 leads to the triol16 which after cyclisation and reductive dehydroxylation furnishes the fragrance compound4.

Auszugsweise vorgetragen auf der 5. wissenschaftlichen Tagung der Österreichischen Pharmazeutischen Gesellschaft am 16. April 1985 in Graz.     

Photofragmentation of NOCl with excimer lasers: Energy distributions of neutral fragments and photoions

The time-of-flight spectra of photofragments produced by a one- and two-photon dissociation of NOCl by 5 eV (248 nm) and 6.4 eV (193 nm) photons from an excimer laser have been measured. The results show that the primary fragments are excited NO and chlorine atoms in the electronic ground state doubl In the case of the one-photon dissociation the NO-fragments are formed highly excited in the X-state. The spectra of excitation for the two different photon energies used in the experiment can be explained by a simple model calculation assuming a direct dissociation from the same intermediate state. The observation of the two-photon dissociation could only be achieved by the analysis of the time-of-flight spectra of NO ions produced by ionizing the primary NO-fragments with the dissociating laser. This method of observation can improve the sensitivity of detection (also for the one-photon process) The results indicate that the NO-fragments from the two-photon dissociation are formed most probably in the Rydberg states of NO.     

Berechnung der Stromdichten und Felder in einem quasineutralen Elektronenstrahlplasma

Zur Berechnung der Stromdichte in einem zylindrischen von Diffusion und Attachment bestimmten Elektronenstrahlplasma wird das Magnetfeld als Vektorpotential eingeführt. Für die entstehende elliptische Differentialgleichung werden die Randbedingungen aufgestellt, die im quasineutralen Fall wegen der an den Rändern verschwindenden Dichte gewissen Einschränkungen unterliegen. Das Randwertproblem ist nur numerisch lösbar. Als Beispiel werden Stromdichten und Feldstärken im Glimmlicht von kontrahierten anomalen Wasserstoff-Glimmentladungen berechnet. Es ergibt sich, daß die Ambipolarität der Radialströme auch bei stärker kontrahierten Entladungen in guter Näherung erfüllt ist. Einige Möglichkeiten für Vergleiche mit Experimenten werden diskutiert. The current density in a cylindrical beam-generated plasma with diffusion and attachment losses is calculated by introducing the magnetic field as vector potential. The boundary-values for the elliptic partial differential equation resulting from this procedure are submitted to certain restrictions for the case of a quasineutral plasma. The boundary-value-problem is solved numerically. As an example, current densities and electrical fields of the negative glow of constricted anomalous H₂-discharges are computed. The results show that even for higher degrees of constriction the radial currents are ambipolar. Some aspects of comparison to experiments are discussed.