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Molecular models in chemistry education at university and upper secondary school - structure of amides

Kolář Karel, Doležal Rafael, Karásková Natálie, Maltsevskaya Nadezhda V., Křížková Šárka

Chemistry-Didactics-Ecology-Metrology

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2019

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R. 24, NR 1-2

45--51

EN

Molecular models derived from results of quantum-chemical calculations present an important category of didactic instruments in chemistry education in upper secondary school and, particularly, at university. These models can be used especially as tools for supporting the students’ understanding by visual learning, which can adequately address complexity of many chemical topics, incorporate appropriate didactic principles, as well as utilize the benefits brought up by the actual information technology. The proposed molecular models are non-trivial examples of didactic application of computational chemistry techniques in illustration of electron interactions in amidic group, namely the interaction of the free electron pair on the nitrogen atom with the carbonyl group and also the interaction of atoms in the amide group with other surrounding atoms in the molecule. By these molecular models it is possible to explain acid-base properties of amides applying knowledge of electron density distribution in the molecules and the resulting electrostatic potential. Presentation of the structure and properties of the amides within education is important also for the reason that amidic functions are involved in many important natural substances (e.g. proteins, peptides, nucleic acids or alkaloids), synthetic macromolecular substances (e.g. Silon) or pharmaceutical preparations (e.g. paracetamol). Molecular models then serve to support better understanding of the structure of these substances and, in relation to it, their properties.

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Distribution of nitrogen compounds in important sections of sugar beets

Bąk P., Antczak-Chrobot A., Wojtczak M.

Biotechnology and Food Science

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2016

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Vol. 80, nr 1

53--61

EN

In literature the beet is often described as consisting of the following technologically important sections: crown, root and tail. The aim of the study was to determine the distribution of nitrogen compounds in the technologically important beet sections of untopped sugar beets with particular emphasis on the content of nitrate and nitrite. The Finezja sugar beet variety had been collected from the clamps in one of the Polish sugar factories in October during 2013/2014 campaign. The untopped sugar beets were divided into three sections: crown, root and tail. The content of total amount of nitrogen, proteinaceous nitrogen, α-amino nitrogen, the sum of the amide and ammonia nitrogen, nitrates and nitrite in these sections were determined. Although the crown of the sugar beet represented only 14.7% of it mass, this section contained on average 30% of the total quantity of α-amino acids as well as amide and ammonia nitrogen.This section contained approximately 77% of the total quantity of nitrate and 88% of nitrite. Untopped sugar beets would introduce much higher amounts of nitrogen compounds in comparison to topped raw material.

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Synthesis, Pharmacological Properties, and Computational Study of 1-[3-(4-Aryl-1-piperazinyl)]propyl Derivatives of Amides of 7 Methyl-3-phenyl-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-5-carboxylic Acid

Sabiniarz A., Śladowska H., Sapa J., Filipek B., Dudek M., Godyń G., Żyta J.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 5

981-998

EN

Two series of novel 1-[3-(4-aryl-1-piperazinyl)]- and 1-[2-hydroxy-3-(4-aryl-1- piperazinyl)]propyl derivatives of amides of 7-methyl-3-phenyl-2,4-dioxo- 1,2,3,4- tetrahydro - pyrido[2,3-d]pyrimidine-5-carboxylic acid (32–46) were synthesized. In the ”writhing syndrome” test all the amides studied displayed an algesic action. The most potent effect was produced by compounds 32, 34, and 46. In the ”hot plate” test only two amides, 34 and 37, showed strong an algesic activity. Further more, most of the investigated substances significantly suppressed spontaneous locomotor activity in mice and prolonged barbiturate sleep of these animals. QSAR analysis of the 14 new and 14 earlier described compounds was made.

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Ion binding properties of 5,11,17,23-tetra-tert-Butyl-25,27-bis(diethylcarbamoylmethoxy)-26,28-bis(diphenylphosphinoylmethoxy)calix[4]arene towards alkaline-earth cations

Yaftian M. R., Abdollahi H., Shokouhi R., Tavakoli M., Matt D.

Chemia Analityczna

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2007

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Vol. 52, No. 1

103-113

EN

The ability of 5,11,17,23-tetra-tert-butyI-25,27-bis(diethylcarbamoylmethoxy)-26.2S-bis(dipheny]phosphinoy[methoxy)calix[4]arene (calix-1) to complex alkaline-earth ions was evaluated by determination of stability constant of respective complexes in methanol and mixed methanol-X solvents (X = acetonitrile or tetrahydrofuran) at 20°C by UV-VIS spec-troscopy. The analysis of the obtained spectra has shown a 1:2 (calix-1/metal) stoichiomet-ric ratio for Ca2 and S2+ complexes, and 1:1 stoichiometry-for Ba2+ in all studied solvents. An addition of either acetonitrile or tetrahydrofuran to methano! increased stability of M-ca!ix-l (M - an alkaline-earth ion) complexes. The results have shown a significantly greater affinity of calix-1 receptor towards calcium ion than to other alkaline-earth ions. To demonstrate analytical applications of the studied calixarene, it has been used as an ionophore in a new PVC coated graphite membrane of Ca2+-selective electrode. The membrane comprised 6% calix-I. 61% solvent mediator {ortho-nitrophenyloctyI ether).30% PVC, and 3% anion excluder (sodium tetraphenylboratc). The electrode exhibited a near-Nernstian response of 30.7 š 0.2 mV/decade over a concentration range of calcium ion of 1 x 10-5- 1 x 10-3 mol L-3 , detection limit was 3.6 x 10-6 mol L-1 . The working pH range of the proposed electrode was 4-7. The electrode was successfully used as a potentiometric sensor in complexometric titration of calcium ion in various solutions.

PL

Oceniono zdolność 5.11,17.23-tetra-fórt-bulyl-25,27-bis(dietyIokarbamoilmetoksy)-26.28--bis(difenylofbsfinoilrnetoksy)kaliks[4]arenu (calix-1) do wiązania w kompleks jonów metali ziem alkalicznych na drodze wyznaczenia stałych wartości odpowiednich kompleksów w metanolu i rozpuszczalnikach mieszanych: metanol-X {X = acetonitryl lub tetrahydrofu-ran), za pomocą spektroskopii UV-VIS w 20°C. Analiza uzyskanych widm wykazała, że stechiometria kompleksów (calix-1—metal) wynosi l :2 dla Ca<2+ i Sr2+ oraz l: l dla Ba;2+ we wszystkich badanych rozpuszczalnikach. Dodatek acetonitrylu lub tetrahydrofuranu do metanolu zwiększa trwałość kompleksów: M-calix-1 (M -jon metalu ziem alkalicznych). Wyniki wskazują na dużo większe powinowactwo receptora calix-1 w stosunku do wapnia niż w stosunku do pozostałych metali ziem alkalicznych. W celu wykazania analitycznych zastosowań badanego kaliksarenu użyto go w charakterze jonoforu w nowej, selektywnej względem Ca2+ elektrodzie z membrana PVC na graficie. Membrana składała się z 6% eteru o-nitrofenylooktyiowego jako mediatora. 30% PVC i 3% tetrafenyloboranu sodu. Elektroda ta wykazywała nieomal Ncrnstowską odpowiedź 30,7 š 0,2 niV/dekadę w zakresie stężeń jonu wapniowego: l x 10-5 x 10-1mol L-1.Roboczy zakres pH nowej elektrody wynosił 4-7. Elektrodę zastosowano z powodzeniem w charakterze potencjometrycznego sensora w kompleksometrycznyrn miareczkowaniu jonów wapniowych w różnych roztworach.

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Lower rim substituted p-tert-butylcalix[4]arenes. Part 10. New Pb(II)-selective electrodes based on tetrasubstituted calix[4]arene with amides

Bocheńska M., Lesińska U.

Chemia Analityczna

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2006

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Vol. 51, No. 6

879-887

EN

Pb(II) - selective electrodes based on Hpophilic calix[4]arenes (compounds 1-3) substituted with amide functionalities have been designed. The electrodes exhibited near-Nernstian characteristics for divalent cations within Pb2+ activity range from 10-1.3 to 10-7.2. The amount of lipophilic anionie component (KTpClPB) in electrode membranes and the influence of inner electrolyte on the electrode behavior and selectivity coefficients have been studied.The electrode with ionophore 3 has been found the best in respect of selectivity coefficients towards Pb(Il) in the presence of copper and cadmium (logKPb.M < -3) and cobalt, nickel, and alkaline earth metal ions (logKPb.M < -4).

PL

Zaprezentowano nowe elektrody Pb(ll)-jonoselektywne oparte na lipofilowych pochodnych kaliks[4]arenu podstawionych I - rżę do wy m i resztami amidowymi (1-3). Elektrody wykazywały prawie nernstowską charakterystykę w zakresie aktywności jonów Pb(II) od 10-1.3 do 10-7.2. Zbadano wpływ ilości soli lipofilowej (KTpCIPB) w membranie oraz elektrolitu wewnętrznego na charakterystykę elektrody oraz szacowane współczynniki selektywności. Stwierdzono, że najlepsze właściwości posiada związek 3, dla którego współczynniki selektywności w skali logarytmicznej wynoszą logK Pb.M < -3 dla kadmu i miedzi jako jonów przeszkadzających i logKPb.M < -4 dla wapnia, strontu, kobaltu i niklu jako jonów przeszkadzających.

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Synthesis of New Diaryl and Dialkyl Diselenides as Potential Vircucides and Antimicrobials

Palus J., Chojnacka M., Piasecki E., Zboińska E., Młochowski J.

Polish Journal of Chemistry

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2004

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Vol.78 /nr 11-12

2117-2126

EN

The synthesis of three new groups of alkyl and aryl diselenides: 2,2'-diselenobisbenzamides, 4,4'-diselenobisbutyramides and 2,2'-di(selenomethyl)bisbenzamides designed as potential virucides and bacteriocides was elaborated. It was based on acylation of free amino group in monoprotected diamines or 4'-aminobenzo-15-crown-5 with corresponding diselenobiscarboxylic acids or their chlorides.

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Spectroscopic Studies and VFF Model calculations on Dynamic and Electrooptic Characteristics of N-H Bonds in Amides

Borisenko V., Morev A. V., Bidulya Y. V., Koll A.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 10

1481-1494

EN

IR spectroscopic studies of propionamide, n-butyramide, benzamide and 2-(F, Cl, Br)- benzamides within the _(NH) and (HNH) absorption range of -NH2 group for the "free" (in CCl4 solutions) molecules and forming complexes with proton acceptor solvents (benzene, toluene, acetonitrile, dimethylformamide, dimethylsulphoxide and hexamethylphosphoramide) have been performed. Modifying the strength of the intermolecular interactions one can achieve the canceling of the primary non-equivalency of the N-H bonds in the -NH2 group of amides. It allows establishing, for the first time, quantitative measures of dynamic (K(NH)) and electrooptic (_/q) characteristics of N-H bonds in amides in framework of the R-NH2 valence force field model. Dynamic and electrooptic non-equivalencies enhance with the increase of the hydrogen bonding strength. For the hydrogen-bonded complexes with acetonitrile, dimethylformamide, dimethylsulfoxide and hexamethylphosphoramide, the dynamic non-equivalency of NH bonds is increased 10-20%, while the electrooptic parameters _1/q1 and _2/q2 grow two or even three times. The electrooptic coupling of the N-H bonds (the parameter _i/qj, where i, j = 1, 2; i _ j) increases with the strength of the hydrogen bonding.

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Hydrogen Peroxide Oxidation of N,N-Dimethylhydrazones Promoted by Selenium compounds, Titanosilicalites or Acetonitrile

Giurg M., Młochowski J., Ambrożak A.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 12

1713-1720

EN

Hydrogen peroxide oxidation of N,N-dimethylhydrazones 1 promoted by title reagents has been investigated. Depending on the substrate nitrile 2 and/or amide 3 accompanied with carboxylic acid 4 and parent carbonyl compounds 5 were obtained. Formation of nitriles 2 with H2O2-acetonitrile system is limited for a few more active substrates. The mechanism of the reaction, based on generated in situ peroxyiminoacetic acid, is presented. A broad spectrum of aliphatic, unsaturated and aromatic nitriles 2 was obtained by oxidation of corresponding N,N-dimethylhydrazones 1 with hydrogen peroxide in the presence of poly(bis-9,10-anthracenyl) diselenide (PADS) (7) as catalyst.

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Preferential solvation of amides by methanol - a comparison of molecular dynamics calculations with the experimental data

Zielkiewicz J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2001

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Vol. 5, No 3

317-329

EN

Using the Kirkwood-Buff theory of solutions, the preferential solvation of the N-methylacet-amide (NMA), N-methylformamide, (NMF), and N,N-dimethylformamide, (DMF), molecule has been investigated in the binary {amide+methanol} mixtures at 313.15 K. Moreover, for the {amide+methanol} mixtures, where amide = NMF, DMF, and NMA, the molecular dynamics calculations at xamide=0.518 were performed. From the obtained molecule-molecule radial distribution functions, (rdf), and atom-atom rdf, it was possible to estimate the local mole fractions around the amide molecule, the orientation effects of molecules within the solvation shell, and a possibility of the formation of complexes. The general picture obtained from analysis of the molecular dynamics results is consistent with the deductions derived from thermodynamic data.