Search results for "Zen"
showing 10 items of 3479 documents
Photolysis of enol acetates and α-bromo derivatives ofo-(acyloxy)acetophenones
1985
UV irradiation of enol acetates 3a – g in benzene gives mainly o-(acetoxy)acetophenones 2 and 2-methylchromones 4. Under the same conditions, the dimethyl derivatives 3h and 3i remain unaffected. The α-bromo ketone 5a gives rise to mixtures of o-(acetoxy)acetophenone (2a), the diketone 6, and/or α-acetoxy-o-hydroxyacetophenone (7), depending on the irradiation conditions. The similarities and differences between the two series of experiments, as well as their possible mechanistic implications, are discussed. Photolyse von Enolacetaten und α-Bromderivaten von o-(Acyloxy)acetophenonen UV-Bestrahlung der Enolacetate 3a – g in Benzol liefert o-(Acetoxy)acetophenone 2 und 2-Methyl-chromone 4 als…
ChemInform Abstract: PHOTOLYSIS OF ENOL ACETATES AND α-BROMO DERIVATIVES OF O-(ACYLOXY)ACETOPHENONES
1985
UV irradiation of enol acetates 3a – g in benzene gives mainly o-(acetoxy)acetophenones 2 and 2-methylchromones 4. Under the same conditions, the dimethyl derivatives 3h and 3i remain unaffected. The α-bromo ketone 5a gives rise to mixtures of o-(acetoxy)acetophenone (2a), the diketone 6, and/or α-acetoxy-o-hydroxyacetophenone (7), depending on the irradiation conditions. The similarities and differences between the two series of experiments, as well as their possible mechanistic implications, are discussed. Photolyse von Enolacetaten und α-Bromderivaten von o-(Acyloxy)acetophenonen UV-Bestrahlung der Enolacetate 3a – g in Benzol liefert o-(Acetoxy)acetophenone 2 und 2-Methyl-chromone 4 als…
Merging shuttle reactions and paired electrolysis for reversible vicinal dihalogenations
2021
Vicinal dibromides and dichlorides are important commodity chemicals and indispensable synthetic intermediates in modern chemistry that are traditionally synthesized using hazardous elemental chlorine and bromine. Meanwhile, the environmental persistence of halogenated pollutants necessitates improved approaches to accelerate their remediation. Here, we introduce an electrochemically assisted shuttle (e-shuttle) paradigm for the facile and scalable interconversion of alkenes and vicinal dihalides, a class of reactions that can be used both to synthesize useful dihalogenated molecules from simple alkenes and to recycle waste material through retro-dihalogenation. The reaction is demonstrated…
On the relations between aromaticity and substituent effect
2019
Aromaticity/aromatic and substituent/substituent effects belong to the most commonly used terms in organic chemistry and related fields. The quantitative description of aromaticity is based on energetic, geometric (e.g., HOMA), magnetic (e.g., NICS) and reactivity criteria, as well as the properties of the electronic structure (e.g., FLU). The substituent effect can be described using either traditional Hammett-type substituent constants or characteristics based on quantum-chemistry. For this purpose, the energies of properly designed homodesmotic reactions and electron density distribution are used. In the first case, a descriptor named SESE (energy stabilizing the substituent effect) is o…
Aminoendgruppenhaltige polymere durch anionische polymerisation von vinylverbindungen mit 3-Dimethylaminopropyllithium als initiator
1975
α-Methylstyrol (in THF) sowie Styrol bzw. Butadien (in Benzol) wurden mit 3-Dimethyl-aminopropyllithium (1) als Initiator homopolymerisiert; dabei wurden aufgrund des Einflusses der tertiaren Aminogruppe bei der Polymerisation in apolarem Medium, verglichen mit der Initiierung durch Butyllithium, Veranderungen der Mikrostruktur der Polymeren beodachtet. Die Molekulargewichte der Polymeren sind hoher, als sich nach dem eingesetzten Monomer/Initiator-Verhatnis berechnete. Der Aminoendgruppengehalt der Polymeren wurde elementaranalytisch sowie NMR-spektroskopisch quantitative bestimmt; die tertiaren Aminoendgruppen konnten mit Methylijodid quantitativ zum quartaren Salz umgesetz werden, mit Br…
Biofiltration of ethylbenzene vapours: influence of the packing material.
2006
In order to investigate suitable packing materials, a soil amendment composed of granular high mineralized peat (35% organic content) locally available has been evaluated as carrier material for biofiltration of volatile organic compounds in air by comparison with a fibrous peat (95% organic content). Both supports were tested to eliminate ethylbenzene from air streams in laboratory-scale reactors inoculated with a two-month conditioned culture. In pseudo-steady state operation, experiments at various ethylbenzene inlet loads (ILs) were carried out. Maximum elimination capacity of about 120 g m(-3) h(-1) for an IL of 135 g m(-3) h(-1) was obtained for the fibrous peat. The soil amendment re…
Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.
2013
Abstract The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene an…
Understanding the affinity of bis-exTTF macrocyclic receptors towards fullerene recognition
2019
A new series of fullerene receptors based on exTTF macrocycles with alkyl ether chains of increasing length is reported. The novel macrocyclic receptors are able to favourably interact with fullerene C60 through a synergistic combination of π–π, CH⋯π and n⋯π noncovalent interactions. We identify that the highest affinity towards C60 recognition is achieved for the host with the tightest fit; that is, the smallest receptor with a cavity large enough to host the buckyball inside (log Ka = 5.2 in chlorobenzene at 298 K). However, besides this expected observation, theoretical calculations evidence that the most stable self-assembling configuration corresponds for all the receptors to an outsid…
Halogen-bonded photoresponsive materials
2015
The aim of the present review is to illustrate to the reader the state of the art on the construction of supramolecular azobenzene-containing materials formed by halogen bonding. These materials include several examples of polymeric, liquid crystalline or crystalline species whose performances are either superior to the corresponding performances of their hydrogen-bonded analogues or simply distinctive of the halogen-bonded species. submittedVersion Peer reviewed
Photoresponsive ionic liquid crystals assembled: Via halogen bond: En route towards light-controllable ion transporters
2017
We demonstrate that halogen bonding (XB) can offer a novel approach for the construction of photoresponsive ionic liquid crystals. In particular, we assembled two new supramolecular complexes based on 1-ethyl-3-methylimidazolium iodides and azobenzene derivatives containing an iodotetrafluoro-benzene ring as XB donor, where the iodide anion acted as an XB acceptor. DSC and X-ray diffraction analyses revealed that the preferred stoichiometry between the XB donors and acceptors is 2 : 1, and that the iodide anions act as bidentate XB-acceptors, binding two azobenzene derivatives. Due to the high directionality of the XB, calamitic superanions are obtained, while the segregation occurring betw…