82 research outputs found
The floristic remains of alpine garden at ruined Beskidenverein hostel in the Babia Góra Massif (Western Beskidy)
Esters with imidazo [1,5-c] quinazoline-3,5-dione ring spectral characterization and quantum-mechanical modeling
1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione reacts with ethyl bromoacetate under mild conditions to give 2-(ethoxycarbonylmethyl)-1-phenyl-6H-imidazo[1,5-c]quinazoline-3,5-dione (MEPIQ) and next 2,6-bis(ethoxycarbonylmethyl)-1-phenylimidazo[1,5-c]quinazoline-3,5-dione (BEPIQ). The products were isolated at high yield and identified on the basis of IR, 1H- and 13C-NMR, UV spectroscopy, and X-ray crystallography. Diester (BEPIQ) can be presented by 16 possible pair of enantiomers. Only one pair of them is the most stable and crystallizes which is shown crystallographic research. Based on quantum-mechanical modeling, with the use of DFT method, which conformers of mono- and diester and why they were formed was explained. It was calculated that 99.93% of the monoester (MEPIQ) is formed at position No. 2 and one pair of the monoester conformers, from six possible, has the largest share (51.63%). These results afforded to limit the number of diester conformers to eight. Unfortunately, the quantum-mechanical calculations performed that their shares are similar. Further quantum-mechanical modeling showed that conformers are able to undergo mutual transformations. As a result only one pair of diester conformers forms crystals. These conformers have substituents in trans position and these substituents are located parallel to imidazoquinazoline ring. This allows for the denser packing of the molecules in the unit cell. © 2017, The Author(s).IGA/FT/2016/004, UTB, Univerzita Tomáše Bati ve ZlíněInterdisciplinary Centre for Mathematical and Computational Modelling in Warsaw [G49-12]; TBU in Zlin [IGA/FT/20017/005
New mono- and diesters with imidazoquinolinone ring- synthesis, structure characterization, and molecular modeling
The objective of the studies was to synthesize and characterize new mono- and diesters with an imidazoquinolin-2-one ring with the use of 2,3-dihydro-2-thioxo-1H-imidazo[4,5-c]-quinolin-4(5H)-ones and ethyl bromoacetate. The products were isolated at high yield and characterized by instrumental methods (IR, 1H-, 13C-, and 15N- NMR, MS-ESI, HR-MS, EA). In order to clarify the places of substitution and the structure of the derivatives obtained, molecular modeling of substrates and products was performed. Consideration of the possible tautomeric structures of the substrates confirmed the existence only the most stable keto form. Based on the free energy of monosubstituted ester derivatives, the most stable form were derivatives substituted at sulfur atom of enolic form the used imidazoquinolones. Enolic form referred only to nitrogen atom no 1. The modeling results were consistent with the experimental data. The HOMO electron densities at selected atoms of each substrate has shown that the most reactive atom is sulfur atom. It explained the formation of monoderivatives substituted at sulfur atom. The diester derivatives of the used imidazoquinolones had second substituent at nitrogen atom no. 3. The new diesters can be used as raw material for synthesis of thermally stable polymers, and they can also have biological activity. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.TBU in Zlin [IGA/FT/2019/10]; Interdisciplinary Centre for Mathematical and Computational Modelling in Warsaw, Poland [G49-12
New localities of meadow plant species between the Vistula and Raba Rivers (northern part of the Puszcza Niepołomicka forest and the adjacent areas)
Unprecedented reaction course of 1-phenyl-2H,6H-imidazo[1,5-c]quinazoline-3,5-dione with 3-M excess of ethylene oxide
The reaction of 1-phenyl-2H,6H-imidazo[1,5-c]quinazolino-3,5-dione (4) with 3-molar excess ethylene oxide was described. The resulting product was characterized by spectroscopic techniques ( 1 H-, 13 C-NMR, IR, and UV) and by X-ray crystallography. It was expected to produce a product of the subsequent reaction in the hydroxyl groups of the initially formed diol—1-phenyl-2,6-bis(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-dione (7) with ethylene oxide (5). However, crystallographic studies revealed that the proper and only product of the reaction is 3-{2-[1,3-bis(2-hydroxyethyl)-2-oxo-4-phenylimidazolidin-5-yl]phenyl}-1,3-oxazolidin-2-one (8). This product was formed by quinazoline ring opening which occurred in the presence of more than 2-molar excess ethylene oxide. In the work, the exemplary reaction mechanism explaining the formation of the unexpected product was proposed. In order to understand the reasons of quinazoline ring opening, the quantum mechanical modeling was performed. Energy of transition states indicated that the reaction with the third mole of ethylene oxide was controlled by kinetics. © 2019, The Author(s).Interdisciplinary Centre for Mathematical and Computational Modelling in Warsaw [G49-12]; European Union from the European Regional Development Fund under the Operational Programme Innovative Economy, 2007-2013; DS budget; internal grant of TBU in Zlin [IGA/FT/2017/005
Linear polyurethanes with imidazoquinazoline rings: preparation and properties evaluation
Abstract: In this work, research concerning the synthesis and properties of linear polyurethanes (PUs) with the imidazoquinazoline rings was represented. Reaction conditions of 2,6-bis(2-hydroxyethyl)-1-phenylimida-zo[1,5-c]quinazoline-3,5-dione (BHPIQ) with 1,6-hexamethylene diisocyanate were determined and optimized. These conditions are adapted to reaction of BHPIQ with 4,4′-diphenylmethane diisocyanate and 2,4-toluene diisocyanate. New PUs with imidazoquinazoline rings were characterized by spectral methods ( 1 H-NMR and IR spectroscopies), which confirm their structures. Their molar masses and dispersity index were measured by size exclusion chromatography method. The wide-angle X-ray scattering and differential scanning calorimetry (DSC) studies have shown that all PUs based on BHPIQ are amorphous. Moreover, thermal properties of PUs were investigated by thermogravimetry analysis, standard DSC, and temperature-modulated DSC methods. During thermogravimetric measurements, the exhaust gases were analyzed by FTIR method. Incorporation of imidazoquinazoline ring into the PU chains escalates their glass transition temperature; thus, their heat resistance was enhanced. Furthermore, their degradation rate and the amount of released degradation products were reduced. The investigated properties of the obtained PUs with imidazoquinazoline rings were compared with those ones of suitable PUs based on 1,4-butanediol. Graphical abstract: Linear polyurethanes were obtained in reaction of 1-phenyl-2,6-bis(2-hydroxyethylimidazo[1,5-c]quinazoline-3,5-dione with hexamethylene 1,6-diisocyanate, 4,4′-diphenylmethane diisocyanate and toluene 2,4-diisocyanate. Their composition and structure were confirmed. The phase contents and thermal properties were investigated[Figure not available: see fulltext.]. © 2019, The Author(s).DS budge
Polylactide-based nonisocyanate polyurethanes: Preparation, properties evaluation and structure analysis
This study investigated the successful synthesis and characterization of nonisocyanate polyurethanes (NIPUs) based on polylactide. The NIPUs were synthesized by a condensation reaction of oligomers with hard segments (HSs) and synthesized carbamate-modified polylactic acid containing flexible segments (FSs). The oligomers with HSs were prepared from phenolsulfonic acid (PSA) or a mixture of PSA and hydroxynaphthalenesulfonic acid (HNSA), urea and formaldehyde. The mixing of oligomeric compounds with different amounts of formaldehyde was carried out at room temperature. Obtained NIPU samples with different hard segment content were tested for their mechanical and thermal properties. The tensile strength (TS) of all NIPU samples increased with an increasing amount of HSs, attaining the maximum value at an HS:FS ratio of 1:3. Samples prepared from PSA and HNSA showed higher tensile strength (TS) without significant change in elongation at break compared to the samples based only on PSA. Thermogravimetric analysis data indicated an absence of weight loss for all samples below 100 °C, which can be considered a safe temperature for using NIPU materials. Maximum degradation temperatures reached up to 385 °C. Fourier transform infrared spectroscopy results confirmed the existence of expected specific groups as well as the chemical structure of the prepared polyurethanes. DSC analysis showed the existence of two characteristic phase transitions attributed to the melting and crystallization of hard segments in the NIPU samples.Ministerstwo Edukacji i Nauki, MNiSWCentre of Polymer Systems (Tomas Bata University in Zlin, Czech Republic), within the project "Strengthening research capacity [CZ.1.05/2.1.00/19.0409, LO1504, 3269/32/P]; Polish Ministry of Science and Higher Educatio
Polymer/layered clay/polyurethane nanocomposites: P3HB hybrid nanobiocomposites - Preparation and properties evaluation
This paper presents an attempt to improve the properties of poly(3-hydroxybutyrate) (P3HB) using linear aliphatic polyurethane (PU400) and organomodified montmorillonite (MMT)—(Cloisite®30B). The nanostructure of hybrid nanobiocomposites produced by extrusion was analyzed by X-ray diffraction and transmission electron microscopy, and the morphology was analyzed by scanning electron microscopy. In addition, selected mechanical properties and thermal properties were studied by thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC. The interactions of the composite ingredients were indicated by FT IR spectroscopy. The effect of the amount of nanofiller on the properties of prepared hybrid nanobiocomposites was noted. Moreover, the non-equilibrium and equilibrium thermal parameters of nanobiocomposites were established based on their thermal history. Based on equilibrium parameters (i.e., the heat of fusion for the fully crystalline materials and the change in the heat capacity at the glass transition temperature for the fully amorphous nanobiocomposites), the degree of crystallinity and the mobile and rigid amorphous fractions were estimated. The addition of Cloisite®30B and aliphatic polyurethane to the P3HB matrix caused a decrease in the degree of crystallinity in reference to the unfilled P3HB. Simultaneously, an increase in the amorphous phase contents was noted. A rigid amorphous fraction was also denoted. Thermogravimetric analysis of the nanocomposites was also carried out and showed that the thermal stability of all nanocomposites was higher than that of the unfilled P3HB. An additional 1% mass of nanofiller increased the degradation temperature of the nanocomposites by about 30 °C in reference to the unfilled P3HB. Moreover, it was found that obtained hybrid nanobiocomposites containing 10 wt.% of aliphatic polyurethane (PU400) and the smallest amount of nanofiller (1 wt.% of Cloisite®30B) showed the best mechanical properties. We observed a desirable decrease in hardness of 15%, an increase in the relative strain at break of 60% and in the impact strength of 15% of the newly prepared nanobiocomposites with respect to the unfiled P3HB. The produced hybrid nanobiocomposites combined the best features induced by the plasticizing effect of polyurethane and the formation of P3HB–montmorillonite–polyurethane (P3HB-PU-MMT) adducts, which resulted in the improvement of the thermal and mechanical properties. © 2023 by the authors.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: 8J20PL026, RP/CPS/2022/00
1,3-Dicyclohexylimidazolidine-2,4,5-trione
The title compound, C15H22N2O3, has been isolated as a by-product of an oxidative cleavage of the C—C bond linking two five-membered rings of 1,3-dicyclohexyl-5-(3-oxo-2,3-dihydrobenzofuran-2-yl)imidazolidine-2,4-dione. Individual molecular units are engaged in weak C=O⋯C=O interactions [O⋯C = 2.814 (10) and 2.871 (11) Å], leading to the formation of supramolecular chains which close pack, mediated by van der Waals contacts, in the bc plane
Polyurethane foams with the contribution of products of hydroxyalkylation of N,N′-bis(2-hydroxyalkyl)oxamides with alkylene carbonates-obtaining and properties
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