Über Verbindungen mit Urotropin-Struktur, 37. Mitt.: Eine neue Methode zur Herstellung von Hydroxy-ketonen und Diketonen sowie ihre Anwendung auf die Synthese des 2,4-Dioxa-adamantan-Ringsystems

Zusammenfassung Es wird eine neue Methode zur Herstellung von Hydroxyketonen und Diketonen beschrieben, die im ersten Schritt der Reaktionsfolge die Umsetzung von Hydroxycarbonsäureestern mit Phenylsulfonalkylmagnesiumbromid zu -Sulfonylketonen erfordert. Diese werden dann im zweiten Schritt mit Al-Amalgam zu den Hydroxyketonen oder den Halbketalen der Diketone entschwefelt. Mit Hilfe dieser Reaktionsfolge gelang auch, ausgehend von 3,5-Dihydroxy-phenylessigsäureester, die Synthese des bisher noch unbekannten Ringsystems des 2,4-Dioxa-adamantans.Herrn Prof. Dr. habil.Friedrich Asinger zum 60. Geburtstag in freundschaftlicher Verbundenheit zugeeignet36. Mitt.:H. Stetter, J. Gärtner undP. Tacke, Chem. Ber.99, 1435 (1966).     

Bestimmung des Gleichgewichts der salpetrigen Säure mit Nitritacidium-Ion auf chemischem Wege

Zusammenfassung Die Struktur des Nitritacidium-Ions¹ kann nach einer Interpretation vonSeel mit der Mesomerie zwischen zwei Grenzzuständen A und B (s. S. 428) erklärt werden. Es ist anzunehmen, daß sich bei einer Verminderung der Aktivität des Wassers der Resonanzzustand des Ions in Richtung von A nach B verschiebt. In sehr schwach perchlorsaurer, wäßriger Lösung läßt sich die Gleichgewichtskonstante der Bildung des Nitritacidium-Ions aus salpetriger Säure und Wasserstoffion aus kinetischen Daten vonHermann Schmid näherungsweise berechnen. In sehr stark perchlorsaurer, wäßriger Lösung läßt sich diese Gleichgewichtskonstante unter Verwendung der SäurefunktionJ ₀ aus Gleichgewichtsmessungen des Salpetrigsäurezerfalles ermitteln. (Der gefundene Wert stimmt mit den vonSeel und vonDeno, Berkheimer, Evans undPeterson aus optischen Untersuchungen erhaltenen Werten und mit dem kürzlich vonGerhard Schmid undU. Neumann mit Hilfe der NO/NO⁺-Elektrode gemessenen Wert größenordnungsmäßig überein.) Der vonChallis undRidd gefundene Mediumeffekt bei der Diazotierung aromatischer Amine in perchlorsaurer, wäßriger Lösung kann durch die oben erwähnte Verschiebung in der Resonanzstruktur des Nitritacidium-Ions erklärt werden.     

The Reagent‐depending Nitration of 1,3‐Dihydroxyacetone Dimer

Two highly energetic nitric acid esters were synthesized from the dimer of dihydroxyacetone. 1,3‐Dinitratoacetone ( 1 ) and its dimer 2,5‐bis(nitratomethyl‐2,5‐nitrato)‐1,4‐dioxane ( 2 ) were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, and elemental analysis. The thermal behavior was investigated with DTA measurements. Although showing the same atomic stoichiometry, dimer 2 shows significantly higher sensitivities measured by BAM methods (drophammer and friction tester). Due to the high oxygen content of 62.2 %, 1 and 2 were evaluated as potential high energy dense oxidizers.     

Structure and Stereochemistry of New Sesquiterpene Esters from Echinacea purpurea (L.) MOENCH. (Preliminary communication)

The structure elucidation of four new constituents from the roots of Echinacea purpurea is described. They are shown to be cinnamoyl esters of sesquiterpene alcohols with a germacrane or a guaiane skeleton. First pharmacological results indicate immunological activities.     

Femtosecond Spectroscopic Studies on the Red Light-Absorbing Form of Oat Phytochrome and 2,3-Dihydrobiliverdin

Abstract— The excited state behavior of the red light-absorbing form of phytochrome (Pr) was studied on the femtosecond time scale. After excitation of Pr with 75 fs laser pulses at 616 nm the kinetics of the transient absorption changes was recorded at selected wavelengths probing mainly the bleaching of the Pr ground-state absorption and the stimulated emission. The kinetic data obtained indicate the population of an excited state with a 3 ps lifetime immediately after excitation. This state precedes the formation of another excited state with a 32 ps lifetime. The decay of the latter state is followed by the appearance of a first product state that is assumed to represent lunii-R. In addition, 2,3-dihydrobiliverdin, which is considered to be an adequate model of the Pr chro-mophore, was included in the femtosecond studies. The absorption difference spectra recorded at various delay times show an immediate bleaching of the ground-state absorption. Simultaneously with bleaching a broad transient absorption appears between 410 and 525 nm. The data analysis yields similar kinetic components as they were observed in the decay of Pr. It is suggested from this finding that within the first tens of picoseconds after excitation the excited-state properties of Pr are mainly determined by the properties of the chromophore itself.     

Origin Identification of Hungarian Honey Using Melissopalynology,Physicochemical Analysis,and Near Infrared Spectroscopy

The objective of the study was to check the authenticity of Hungarian honey using physicochemical analysis, near infrared spectroscopy, and melissopalynology. In the study, 87 samples from different botanical origins such as acacia, bastard indigo, rape, sunflower, linden, honeydew, milkweed, and sweet chestnut were collected. The samples were analyzed by physicochemical methods (pH, electrical conductivity, and moisture), melissopalynology (300 pollen grains counted), and near infrared spectroscopy (NIRS:740–1700 nm). During the evaluation of the data PCA-LDA models were built for the classification of different botanical and geographical origins, using the methods separately, and in combination (low-level data fusion). PC number optimization and external validation were applied for all the models. Botanical origin classification models were >90% and >55% accurate in the case of the pollen and NIR methods. Improved results were obtained with the combination of the physicochemical, melissopalynology, and NIRS techniques, which provided >99% and >81% accuracy for botanical and geographical origin classification models, respectively. The combination of these methods could be a promising tool for origin identification of honey.     

Control of Excited‐State Conformations in B,N‐Acenes

We present a new concept to control the conformations of molecules in the excited state through harvesting negative hyperconjugation. The strategy was realized with the 2,3,1,4‐benzodiazadiborinane scaffold, which was prepared by a new synthetic procedure. Photochemical studies identified dual light emission, which was assigned to well‐defined conformers. The emission at longer wavelength can be switched off by restricting the rotational degrees of freedom in the solid state as well as by controlling the energy levels of the excited states through adjusting the solvent polarity.