FG Organische Chemie

27 Items

Recent Submissions
On the crucial role of isolated electronic states in the thermal reaction of ReC+ with dihydrogen

Li, Jilai ; Geng, Caiyun ; Weiske, Thomas ; Schwarz, Helmut (2020-03-17)

Presented here is that isolated, long-lived electronic states of ReC+ serve as the root cause for distinctly different reactivities of this diatomic ion in the thermal activation of dihydrogen. Detailed high-level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT-ICR mass spectrometry. The origin for the existence of these long-liv...

Counter-intuitive gas-phase reactivities of [V2]+ and [V2O]+ towards CO2 reduction: Insight from electronic structure calculations

Li, Jilai ; Geng, Caiyun ; Weiske, Thomas ; Schwarz, Helmut (2020-02-26)

[V2O]+ remains “invisible” in the thermal gas-phase reaction of bare [V2]+ with CO2 giving rise to [V2O2]+; this is because the [V2O]+ intermediate is being consumed more than 230 times faster than it is generated. However, the fleeting existence of [V2O]+ and its involvement in the [V2]+ → [V2O2]+ chemistry are demonstrated by a cross-over labeling experiment with a 1:1 mixture of C16O2/C18O2,...

Characterization of the Plant-Associated Bacterial Microbiota of the Mexican Medicinal Species Bouvardia ternifolia

Villalobos-Flores, Loan Edel ; Espinosa-Torres, Samuel David ; Hernández-Quiroz, Fernando ; Piña-Escobedo, Alberto ; Cruz-Narváez, Yair ; Velázquez-Escobar, Francisco ; Süssmuth, Roderich ; García-Mena, Jaime (2021-01-13)

Though therapeutic compounds can be extracted directly from medicinal plant tissues; it is now known that many phytotherapeutic compounds are actually produced by associated microorganisms or due to their interaction with the plant. Bouvardia ternifolia is a medicinal plant that can be considered a potential source of therapeutic compounds, such as the antitumoral molecule bouvardin. We charact...

Remote C-H functionalization and photochromic properties investigation of 3H-naphthopyrans

Qi, Longying (2020)

Naphthopyrans, as an important class of organic photochromic compounds, have a wide application in ophthalmic lenses and other fields, such as molecular electronic devices, photochromic thin films, etc. The substituents have a great influence on the photochromic behaviors of naphthopyrans. Hence, the research about relationship between substituents and photochromic properties as well as the met...

A Simple Nickel Catalyst Enabling an E‐Selective Alkyne Semihydrogenation

Thiel, Niklas Olof ; Kaewmee, Benyapa ; Tran Ngoc, Trung ; Teichert, Johannes F. (2019-11-06)

Stereoselective alkyne semihydrogenations are attractive approaches to alkenes, which are key building blocks for synthesis. With regards to the most atom economic reducing agent dihydrogen (H 2 ), only few catalysts for the challenging E ‐selective alkyne semihydrogenation have been disclosed, each with a unique substrate scope profile. Here, we show that a commercially available nickel cataly...

Alternative Biochemistries for Alien Life: Basic Concepts and Requirements for the Design of a Robust Biocontainment System in Genetic Isolation

Diwo, Christian ; Budisa, Nediljko (2018-12-28)

The universal genetic code, which is the foundation of cellular organization for almost all organisms, has fostered the exchange of genetic information from very different paths of evolution. The result of this communication network of potentially beneficial traits can be observed as modern biodiversity. Today, the genetic modification techniques of synthetic biology allow for the design of spe...

Development and investigation of photoswitchable DTE(OMe)-fluorophore conjugates

Ziebart, Nandor (2019)

Photoswitchable modulation of fluorescence became a field of high interest for different applications, as optical devices. The detailed nature of energy and electron transfer in conjugates on semiconductor surfaces could lead to a better understanding and future applications in sensors or optoelectronics. Former work group projects showed efficient on off energy transfer in photoswitchable DTE...

Isolation of the Phytochrome Chromophore. The Cleavage Reaction with Hydrogen Bromide

Rüdiger, Wolfhart ; Brandlmeier, Thomas ; Blos, Inge ; Gossauer, Albert ; Weller, Jens-Peter (1980)

The cleavage of the bilin chromophore from C-phycocyanin with hydrogen bromide yields 3E-configurated phycocyanobilin (4) as the major and 3 Z-configurated phycocyanobilin (5) as the minor reaction product. The reaction of synthetic 3E-configurated phytochromobilin (2) with hydrogen bromide and methanol leads only to a methanol adduct at the C-18 side chain (7) whereas the same reaction with th...

Frontorbitale und 1.2-Hydridwanderungen in Carbeniumionen

Frenking, Gernot ; Schwarz, Helmut (1981)

For various carbenium ions it is shown that the energy value and the degree of localization of the LUMO have a significant influence on the energy barriers of 1,2-hydrogen shifts. The structures of the transition states are in line with the Hammond-Postulate.

Zur McLafferty-Umlagerung bei Radikalkationen von Phenylpyridylalkanonen

Richter, Bernd ; Schwarz, Helmut (1981)

A detailed investigation concerning the genesis of McLafferty rearrangement products from molecular ions of phenyl pyridyl alkanones reveals the following features: 1) The various products are not formed by competitive dissociations of the molecular ion. Most of the relevant fragment ions are generated from the primary McLafferty product of a hydrogen transfer to the ionized carbonyl group (M+·...

Protonkatalysierte Wasser-Abspaltung aus 1-Dekalon und 8α-Methyl-1-dekalon in the Gasphase. Verlust der stereochemischen Integrität der cis/traras-Ringverknüpfung bei [MH]+ -Ionen

Wrolfschütz, Roland ; Halim, Hermann ; Schwarz, Helmut (1982)

Water loss from protonated gaseous 1-decalon and 8α-methyl-1-decalon under the condition of chemical ionisation mass spectrometry proceeds via at least three distinct pathways, all of which commences with a [1.2]-hydrogen or [1.2]-methyl migration, thus giving rise to the formation of the central intermediate 10. H2O loss from 10 proceeds either directly, involving a hydrogen from the position ...

Zur intermediären Existenz von Ethylenfluoronium-Ionen in der Gasphase

Ciommer, Bernhard ; Schwarz, Helmut (1983)

The long-sought ethylen fluoronium ion (2) is generated as an intermediate in the dissociative ionization of 1-fluoro-2-(p-methyl)phenoxy ethane (4). However, prior to collisionally induced dissociation 2 undergoes ring-opening, associated with hydrogen migration, to form 1-fluoroethyl cation (3). Other decomposition pathways of the molecular ions of 4 involve (i) direct formation of 3 via a co...

Discotic Mesophases of the Hexakis(alkylsulfono)benzene Series: Characterization by Differential Scanning Calorimetry, Optical Microscopy and Nuclear Magnetic Resonance Spectroscopy

Praefcke, K. ; Poules, W. ; Scheuble, B. ; Poupko, R. ; Luz, Z. (1984)

Members of the Hexakis(alkylsulfono)benzene series 4, containing 7 to 15 carbon atoms per alkyl chain (4 c-k), exhibit one and possibly several liquid crystalline discotic mesophases. The mesophases are uniaxial and most probably have a columnar structure. Their anisotropic magnetic susceptibility is negative and in sufficiently strong magnetic fields they align with the director perpendicular ...

New Triterpene from Conyza aegyptiaca L

Metwally, Mohamed Abbas (1989)

From the large genus Conyza (tribe Astereae, family Compositae) about 10% of the approximately 2000 species in this tribe have been subjected to chemical scruting. However, work has been confined largely to root constituents. Among these, polyacetylenes, polyenes and related substances and, in certain groups, coumarins are very characteristic. Less widely distributed, perhaps because they are l...

IR-spektroskopische Charakterisierung von organisch-funktionalisierten Monolagen und Immobilisierung von Peptiden auf Silizium Oberflächen

Borowski, Anne (2018)

Das Interesse an der Entwicklung und Forschung von Biosensoren hat sich in den letzten Jahren stetig gesteigert. Die Verwendung von optischen, auf SOI (silicon-on-isulator) basierenden Sensoren, bietet die Möglichkeit Protein-Ligand-Wechselwirkungen auf ihre thermodynamischen und kinetischen Eigenschaften zu untersuchen. Das Konzept von selbstassemblierten Monoschichten (SAMs) mit definierten o...

Photoswitchable Monolayers on Si(111) and Si(100) Surfaces

Vlajić, Marina (2018)

Photochromic compounds, that exhibit stable and reversible change of their physical and chemical properties upon light absorption, present great potential for development of new “smart” materials. Thus, their attachment to the solid surfaces and nanostructures showed prospective in development of novel photosensitive smart materials. In that context, present work dealt with preparation of photo...

Kooperative Si–H-Bindungsaktivierung an einem Ru–S-Komplex mit axial chiralem Rückgrat

Wübbolt, Simon (2018)

Die vorliegende Dissertation widmet sich der simultanen Erzeugung von Siliciumelektrophilen und den entsprechenden Metallhydriden für die asymmetrische Katalyse durch kooperative Si–H-Bindungsaktivierung entlang einer Ruthenium–Schwefel-Bindung. Mit Hilfe heterolytischer Si–H-Bindungsspaltung mit Rutheniumthiolatkomplexen können Hydrosilane in ein schwefelstabilsiertes Silyliumion und ein Ruth...

Bor-Lewis-Säure-katalysierte Aktivierung von substituierten Cyclohexa-1,4-dienen: Anwendungen als Transferreagenzien in der Synthesechemie

Keeß, Sebastian (2017)

Die vorliegende Arbeit widmet sich der Entwicklung geeignet substituierter Cyclohexa-1,4-diene und deren Anwendung als sicher handhabbare Ersatzstoffe für als Reinsubstanz gefährliche Chemikalien in Lewis-Säure-katalysierten Transferreaktionen. Im ersten Teil dieser Dissertation wurde im Rahmen einer systematischen Untersuchung der Einfluss verschiedener Faktoren auf die im Jahr 2013 von Simonn...

Surface enhanced resonance Raman detection of a catalytic intermediate of DyP-type peroxidase

Todorovic, Smilja ; Hildebrandt, Peter ; Martins, Ligia O. (2015)

We report herein the vibrational spectroscopic characterisation of a catalytic intermediate formed by the reaction of H2O2 with DyP-type peroxidase immobilised on a biocompatible coated metal support. The SERR spectroscopic approach is of general applicability to other peroxidases which form relatively stable catalytic intermediates.

Ultrafast coherent oscillations reveal a reactive mode in the ring-opening reaction of fulgides

Slavov, C. ; Bellakbil, Nabil ; Wahl, J. ; Mayer, Kerstin ; Rück-Braun, Karola ; Burghardt, I. ; Wachtveitl, Josef ; Braun, M. (2015)

The ultrafast ring-opening reaction of photochromic fulgides proceeds via conical intersections to the ground state isomers involving activation barriers in the excited state. The coherent oscillations observed in the femtosecond transient absorption signal of a methyl-substituted indolylfulgide were analysed in the framework of vibrational wavepackets to expose a dominant low-frequency mode at...