Search results for "Nagel"
showing 10 items of 25 documents
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās
2021
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās. Gradovska L., darba vadītāji Dr.h.ķīm., prof. Zicmanis A., Dr.chem. Baķis E. Maģistra darbs, 59 lappuses, 31 attēls, 5 tabulas, 43 literatūras avoti, 1 pielikums. Latviešu valodā. Literatūras apskatā apkopota informācija par biežāk aprakstītajiem jonu šķidrumiem un polietilēnglikola funkcionalizētajem jonu šķidrumiem, to iegūšanu un izmantošanas iespējām organiskajā katalīzē. Eksperimentālajā daļā sintezēti polietilēnglikola, spirtu un alkilvirkņu funkcionalizētie imidazolija rindas jonu šķidrumi, kuri izmantoti kā katalizatori un reakcijas vide Knēvenāgela kondensācijā. Reakcijas konversija atkarībā no laika novērtēta, izma…
Dialkylimidazolium dimethyl phosphates as solvents and catalysts for the Knoevenagel condensation reaction
2014
Abstract The reaction between benzaldehyde and ethyl cyanoacetate is investigated in 1,3-dialkylimidazolium salts as solvents. The impact of both ions in these ionic liquids on the yield of the condensation reaction product is examined. Potentiometric titrations are employed for quantitative analyses of the best ionic liquids, revealing these to be 1,3-dialkylimidazolium dimethyl phosphates.
Síntesis de derivados del HMF mediante la reacción de condensación de Knoevanagel utilizando catalizadores básicos heterogéneos
2017
En la presente investigación se realizó la valoración de una molécula plataforma derivada de la biomasa, el 5-hidroximetilfurfural (HMF) mediante su conversión en compuestos de interés como monómeros para la obtención de nuevos materiales poliméricos. Concretamente, se llevo a cabo la síntesis de bis 5-((2´,2´-dicianovinil)-furfuril) éter mediante un proceso en cascada que implica como primera etapa la autoeterificación del HMF (dando lugar al éter OBMF), catalizada por el aluminosilicato mesoporoso MCM-41, seguida de la condensación de Knoevenagel de los grupos formil del OBMF con compuestos con grupos metilenos activos en presencia de catalizadores básicos heterogéneos. Además se optimizó…
A DFT study of IRMOF-3 catalysed Knoevenagel condensation
2011
It has been recently reported that IRMOF-3 [Gascon et al., J. Catal, 2009, 261, 75] may behave as a basic catalyst, active in the Knoevenagel condensation. In particular, it has been shown that the basicity of aniline-like amino moieties is enhanced, along with the catalytic activity, when incorporated into MOF structures. The computational study here was aimed at finding possible atomistic explanations of the increased basicity and catalytic activity of the IRMOF-3 embedded aniline groups, experimentally claimed. It was, moreover, aimed at guessing a reaction mechanism for the IRMOF-3 catalysed Knoevenagel condensation of benzaldehyde and ethyl-cyanoacetate. Within the DFT framework we hav…
Rateless Codes Performance Analysis in Correlated Channel Model for GEO Free Space Optics Downlinks
2012
First Evidence of Tris(catecholato)silicate Formation from Hydrolysis of an Alkyl Bis(catecholato)silicate
2022
The hydrolysis of 3-ammoniumpropylbis(catecholato)silicate 1, giving two different silica-based materials containing different amounts of tris(catecholato)silicate, is reported. The latter species can be formed through an attack of catechol to the silicon atom in the pentacoordinate complex, in which the silicon-carbon bond is further activated toward electrophilic proton cleavage. The Knoevenagel reaction was used as a probe in order to test the availability of functional groups on the surface of such materials.
Site-selectivity control in hetero-Diels-Alder reactions of methylidene derivatives of lawsone through modification of the reactive carbonyl group: a…
2019
A new perspective on the reactivity of hydroxyquinones was revealed as an acetal derivative of lawsone was synthesized, isolated, and used in tandem Knoevenagel/hetero-Diels-Alder reactions catalyzed by S-proline. The intermediate alkylidene-1,3-diones that were formed in situ reacted with electron rich alkenes to predominantly afford pyrano-1,2-naphthoquinone (β-lapachone) derivatives along with the isomeric pyrano-1,4-naphthoquinone (α-lapachone) derivatives in high to excellent total yields. Interestingly, the highly reactive arylidene-1,3-dione derivatives were found to be stable and isolable. DFT calculations suggest that these hetero-Diels-Alder reactions have a high polar character, …
Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis
2020
Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission ele…
Synthesis and characterization of polyene chromophores with hydroxyl functionalization
2008
Abstract Eight hydroxyl functionalized donor–acceptor polyene chromophores 3–10 were synthesized and characterized. Knoevenagel condensation reaction of aromatic polyenals with 2-cyanoacetamide derivatives was utilized to synthesize chromophores with all-E configuration. Chromophores of this kind can be attached covalently to polymers or functionalized with dendrons in order to tune the properties. The structures of the molecules were verified by 1H NMR, 13C NMR, ESI-TOF mass spectrometry and UV–vis measurements. Reduced bond-length alternation of the molecules in DMSO-d6 solution were observed by calculating the average difference of the vicinal coupling constants between adjacent CH CH an…
TWO-LANE TRAFFIC WITH PLACES OF OBSTRUCTION TO TRAFFIC
2004
As the Nagel–Schreckenberg model (NaSch model) became known as a realistic approach to describe traffic flow on single-lane streets, this model was extended to two-lane traffic by several groups. On the base of our two-lane model, we will now investigate the impact of a place of obstruction, e.g., because of road works, on partial fractions, densities and mean velocities.