scholarly journals Acenaphthoquinoxaline Derivatives as Dental Photoinitiators of Acrylates Polymerization

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4881
Author(s):  
Ilona Pyszka ◽  
Beata Jędrzejewska
Keyword(s):  
Hydrogen Atom Transfer ◽  
Polymerization Rate ◽  
Electron Donors ◽  
Polymerization Reaction ◽  
Lower Amount ◽  
Aromatic Rings ◽  
Intermolecular Electron Transfer ◽  
Chain Reaction ◽  
Electron Donating Groups ◽  
Heat Released

A series of dyes based on the acenaphthoquinoxaline skeleton was synthesized. Their structure was modified by introducing electron-withdrawing and electron-donating groups, increasing the number of conjugated double bonds and the number and position of nitrogen atoms, as well as the arrangement of aromatic rings (linear or angular). The dyes were investigated as a component in the photoinitiating systems of radical polymerization for a potential application in dentistry. They acted as the primary absorber of visible light and the acceptor of an electron, which was generated from a second component being an electron donor. Thus, the radicals were generated by the photoinduced intermolecular electron transfer (PET) process. Electron donors used differed in the type of heteroatom, i.e., O, S and N and the number and position of methoxy substituents. To test the ability to initiate the polymerization reaction by photoinduced hydrogen atom transfer, we used 2-mercaptobenzoxazole as a co-initiator. The effectiveness of the photoinitiating systems clearly depends on both the modified acenaphthoquinocaline structure and the type of co-initiator. The lower amount of heat released during the chain reaction and the polymerization rate comparable to this achieved for the photoinitiator traditionally used in dentistry (camphorquinone) indicates that the studied dyes may be valuable in this field.

Catalyst- and Silane- Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Kousuke Ebisawa ◽  
Kana Izumi ◽  
Yuka Ooka ◽  
Hiroaki Kato ◽  
Sayori Kanazawa ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Hydrogen Atom Transfer ◽  
Biologically Active ◽  
Atom Transfer ◽  
High Concentration ◽  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction

Catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal catalyzed-hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of non-conjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, <i>N</i>-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect in the solvent, thermal dependency, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

scholarly journals Submicrometric Fibrillar Structures of Codoped Polyaniline Obtained by Co-oxidation Using the NaClO/Ammonium Peroxydisulfate System: Synthesis and Characterization

2017 ◽  
Vol 57 (4) ◽  
Author(s):  
Jorge Enrique Osorio-Fuente ◽  
Carlos Gómez-Yáñez ◽  
María De los Ángeles Hernández-Pérez ◽  
Mónica De la Luz Corea-Téllez
Keyword(s):  
Electrical Conductivity ◽  
Co Oxidation ◽  
Sodium Hypochlorite ◽  
Polymerization Rate ◽  
Synthesis And Characterization ◽  
Aromatic Rings ◽  
Co Doping ◽  
Ammonium Peroxydisulfate ◽  
Structure Morphology ◽  
Morphology Changes

A mixture of ammonium peroxydisulfate and sodium hypochlorite (NaClO) (co-oxidating system) were used to obtain polyaniline (PANi) doped with HCl and camphorsulfonic acid (CSA) (co-doping). The effect of HCl/CSA ratio added during polymerization on structure, morphology and electrical conductivity of the conducting polymer was investigated. When NaClO is used, the polymerization rate is substantially increased and the morphology changes from micrometric granular to nanometric fibrillar. CSA was used as complementary dopant but also to improve the solubility of PANi in common solvents. However, results suggest that quinone-like heterocycles containing carbonyl radicals as well as phenazine-type aromatic rings might be impeding an efficient doping in detriment of the conductivity.

scholarly journals Oxidative Photocyclization of Aromatic Schiff Bases in Synthesis of Phenanthridines and Other Aza-PAHs

2020 ◽  
Vol 21 (16) ◽  
pp. 5868
Author(s):  
Martin Kos ◽  
Jaroslav Žádný ◽  
Jan Storch ◽  
Vladimír Církva ◽  
Petra Cuřínová ◽  
...  
Keyword(s):  
Schiff Bases ◽  
Reaction Rate ◽  
Potential Method ◽  
Biologically Active ◽  
Aromatic Rings ◽  
Order Of Magnitude ◽  
Substituent Constants ◽  
Aromatic Imines ◽  
Aromatic Systems ◽  
Electron Donating Groups

The oxidative photocyclization of aromatic Schiff bases was investigated as a potential method for synthesis of phenanthridine derivatives, biologically active compounds with medical applications. Although it is possible to prepare the desired phenanthridines using such an approach, the reaction has to be performed in the presence of acid and TEMPO to increase reaction rate and yield. The reaction kinetics was studied on a series of substituted imines covering the range from electron-withdrawing to electron-donating substituents. It was found that imines with electron-withdrawing substituents react one order of magnitude faster than imines bearing electron-donating groups. The 1H NMR monitoring of the reaction course showed that a significant part of the Z isomer in the reaction is transformed into E isomer which is more prone to photocyclization. The portion of the Z isomer transformed showed a linear correlation to the Hammett substituent constants. The reaction scope was expanded towards synthesis of larger aromatic systems, namely to the synthesis of strained aromatic systems, e.g., helicenes. In this respect, it was found that the scope of oxidative photocyclization of aromatic imines is limited to the formation of no more than five ortho-fused aromatic rings.

Investigation of the Polymers Formed in Reactor Irradiated Aniline and Pyridine

1973 ◽  
Vol 51 (23) ◽  
pp. 3860-3865 ◽  
Author(s):  
Mahmoud F. Barakat ◽  
Fawzi M. Abdelkerim
Keyword(s):  
Polymer Chains ◽  
Polymerization Reaction ◽  
Aromatic Rings ◽  
Radioactive Materials ◽  
Initial Amount ◽  
Great Capacity ◽  
Polymer Formation ◽  
Pure Compounds ◽  
Recoil Atoms ◽  
Individual Polymer

In reactor irradiated aniline or pyridine most of the radiocarbon generated by the 14N(n,p)14C reaction was found preferentially localized in a polymer-like material, brown in color, frequently lustrous and constituting 15–30% of the initial amount of the irradiated material. This stimulated us to try to obtain an idea about the chemical groupings existing in these highly radioactive materials and thereafter to deduce their possible formation pathways.By comparing the i.r. spectra of these polymers with those of the corresponding pure compounds it was possible to detect some changes in the spectra on polymerization and consequently it was possible to identify some basic structural groups existing. Based on these findings some polymerization reaction mechanisms have been suggested. In general, polymer formation was assumed to take place through the formation of polymerization centers produced by the rupture of the aromatic rings to give highly unsaturated fragments and radicals. These are capable of adding different radicals and fragments formed in the irradiated material by radiolysis or by the action of energetic recoil atoms. Cross linking between individual polymer chains was observed. The preferential localisation of 14C in the polymer fraction could be attributed to the great capacity of the recoil atoms to form reactive secondary species such as 14CH3•, 14CH2••, or 14CH••• which participate in polymer formation.

scholarly journals Monitoring of cytomegalovirus (CMV) infection in solid organ transplant recipients: quantitation of CMV DNAemia by two real-time polymerase chain reaction assays

2016 ◽  
Vol 31 (3) ◽  
Author(s):  
Angela Chiereghin ◽  
Giulia Piccirilli ◽  
Gabriele Turello ◽  
Diego Squarzoni ◽  
Claudia Pavia ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Real Time ◽  
Quantitative Result ◽  
Lower Amount ◽  
Solid Organ ◽  
Transplant Recipients ◽  
Chain Reaction ◽  
Clinical Value ◽  
Polymerase Chain ◽  
Cmv Dnaemia

<em>Background and aim:</em> Quantification of cytomegalovirus (CMV) DNAemia is essential in clinical management of post-transplant infection. We evaluated the performances of two quantitative real-time polymerase chain reaction (PCR) assays. <br /><em>Materials and Methods</em>: 114 serial whole blood samples collected from 14 actively infected transplant recipients were processed by Abbott RealTime CMV PCR kit (Abbott Molecular) and CMV ELITe MGB™ kit (ELITech Group). The Quality Control for Molecular Diagnostics human CMV panels was also tested. <br /><em>Results</em>: Sixteen (14%) samples resulted negative and 59 (51.7%) positive with a quantitative result for both assays. In the 59 samples, the coefficient of correlation was 0.856. Bland-Altman analysis showed a mean difference of &lt;0.11 log10 copies/mL (standard deviation=0.38 log10 copies/mL). The assays gave CMV-DNA loads differing by 1 log10 DNA copies/mL in 57 samples (96.6%) and by &lt;0.5 log10 DNA copies/mL in 48 samples (81.3%). Eleven (9.6%) samples were positive with a quantitative result with Abbott and negative with ELITech. Sixteen (14%) positive samples with a quantitative result for Abbott resulted positive but below the lower limit of quantification (LLQ) for ELITech. Twelve (10.5%) samples resulted negative with ELITech and positive but below the LLQ with Abbott. No samples were positive with ELITech and negative with Abbott. <br /><em>Conclusions</em>: The assays showed a good correlation between CMVDNA levels detected and variation in CMV-DNA &lt;0.5 log10 was observed in the majority of the samples. The viral load kinetic profiles of the assays were overlapping in all patients, but Abbott showed higher sensitivity in samples containing lower amount of DNA. The clinical value of this greater sensitivity requires further investigation.

Mechanism-based QSAR approach to the study of the toxicity of endocrine active substances

2003 ◽  
Vol 75 (11-12) ◽  
pp. 2363-2373 ◽  
Author(s):  
C. D. Selassie ◽  
R. Garg ◽  
S. Mekapati
Keyword(s):  
Binding Affinity ◽  
Binding Affinities ◽  
Electronic Effects ◽  
Aromatic Rings ◽  
Substituted Phenols ◽  
Common Features ◽  
Relative Binding ◽  
Qsar Models ◽  
Electron Donating Groups ◽  
Active Substances

Mechanism-based QSAR models for interactions between various ligands and the estrogenic receptor are developed by using well-developed physicochemical parameters. Common features of these QSARs are identified, and deficiencies in some datasets are highlighted. The relative binding affinities of various substituted hexestrols to estrogen receptors are examined in terms of their steric, electronic, and hydrophobic attributes. Different QSARs for hexestrols and tamoxifens reveal that steric effects are of overriding importance in variations of binding affinity. In the few cases where a large number of diverse substituents are located on aromatic rings, electronic effects emerge and suggest that electron-donating groups enhance binding to the receptor while hydrophobicity plays a marginal role in decreasing binding affinity. With substituted phenols bearing alkyl-type substituents and substituted hydroxy-biphenyls, the binding is strictly dependent on hydrophobicity and size. These QSAR models are described in detail and examined together to illustrate the utility of lateral validation in mechanistic interpretation.

Electron spectra of 1-tetralone, homophthalide, 3,4-dihydroisoquinoline, and 3,4-dihydroisoquinolinium compounds

1980 ◽  
Vol 45 (7) ◽  
pp. 1950-1958 ◽  
Author(s):  
František Šantavý ◽  
Ivo Válka
Keyword(s):  
Alkaline Medium ◽  
Electron Donors ◽  
Aromatic Nucleus ◽  
Alkaline Ph ◽  
Electron Spectra ◽  
Electron Donating Groups

The electron spectra of 1-indanone (I), 1-tetralone (II), phthalide (III), homophthalide (IV), 3,4-dihydroisoquinoline (VII), and 3,4-dihydroisoquinolinium (VIII) compounds, substituted by electron donating groups (hydroxy, methoxy or methylenedioxy groups) on the aromatic nucleus, resemble when the electron donors are at the same distance from the electron accepting substituent. In the compounds VII and VIII, the electron spectra were measured in ethanol at acidic and alkaline pH, and the change in the spectra of the compounds VIII in alkaline medium was clarified.

Effects of meso-diarylamino group of porphyrins on optical and electrochemical properties

2020 ◽  
Vol 24 (01n03) ◽  
pp. 67-74 ◽  
Author(s):  
Tomohiro Higashino ◽  
Yamato Fujimori ◽  
Issei Nishimura ◽  
Hiroshi Imahori
Keyword(s):  
Functional Materials ◽  
Oxidation Potential ◽  
Electron Donors ◽  
Charge Transfer Complexes ◽  
Oxidative Amination ◽  
Amination Reaction ◽  
Hole Transporting ◽  
Porphyrin Core ◽  
Electron Donating Groups ◽  
Hole Transporting Materials

Introduction of an electron-donating meso-diarylamino group into a porphyrin core affords its broadened and red-shifted absorption and raises the HOMO level of the porphyrin. In this regard, porphyrins with multiple meso-diarylamino groups are expected to show unique optical and electrochemcial properties depending on the number of the meso-diarylamino groups. Herein, we report a series of porphyrins with a different number of the meso-diarylamino groups. They were prepared by the iodine(III)-mediated oxidative amination reaction of the corresponding meso-free porphyrins. With increasing the number of the meso-diarylamino groups, both red shifts and broadening in the absorption and negative shifts in the oxidation potential were observed. Notably, the oxidation potential of the porphyrin with four meso-diarylamino groups is comparable to that of tetrathiafulvalene, which is one of representative electron donors, suggesting the potential utility of multiply meso-aminated porphyrins as hole-transporting materials and as electron donors forming charge-transfer complexes with electron acceptors. We believe that this study sheds light on porphyrins with multiple electron-donating groups as organic functional materials.

Synthesis and characterization of crystalline poly(N-(2-hydroxyethyl)aniline) microspheres

2016 ◽  
Vol 29 (2) ◽  
pp. 227-236 ◽  
Author(s):  
HM Abd El-Salam ◽  
HG Askalany
Keyword(s):  
Initial Rate ◽  
Polymerization Rate ◽  
Proton Nuclear Magnetic Resonance ◽  
Polymerization Reaction ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Ammonium Persulphate ◽  
X Ray ◽  
One Step

Poly( N-(2-hydroxyethyl)aniline) microsphere was prepared in aqueous hydrochloric acid (HCl) in one step, using ammonium persulphate as an oxidant. The effect of monomer, oxidant, HCl concentrations and temperature on polymerization rates was investigated. The data show that polymerization rate increases with increasing reactant concentrations. In addition, the initial rate increases with raising the temperature. The apparent activation energy found was 57.4319 kJ/mole. Also, Δ H* and Δ S* found were 55.0691 kJ/mole and 78.3662 J/mole K respectively. Infrared and proton nuclear magnetic resonance spectroscopies, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and elemental analysis characterize the obtained polymer sample to confirm the suggested structure. The mechanism of the polymerization reaction are discussed.

Sign in / Sign up

Export Citation Format

Share Document