Classical chemical sciences
Novel 4-substituted pyran-2-one derivatives were synthesized by condensation of 6-methylpyran-2-ones and corresponding 2-aminobenzothiazoles. Condensation of 4-chloro-6-methyl-2H-pyran-2-one 2a and 2-aminobenzothiazoles 3(a-c) afforded corresponding 4-(2-benzothiazolylamino)-6-methyl-2H-pyran-2-one 4a, 4-(4-methyl-2-benzothiazolylamino)-6-methyl-2H-pyran-2-one 4b and 4-(5,6-dimethyl-2-benzothiazolylamino)-6-methyl-2H-pyran-2-one 4c. By condensation of 4-chloro-3-nitro-6-methyl-2H-pyran-2-one 2b and 2-aminobenzothiazoles 3(a-d), 4-(2-benzothiazolylamino)-3-nitro-6-methyl-2H-pyran-2-one 4d and 4-(6-ethoxy-2-benzothiazolylamino)-3-nitro-6-methyl-2H-pyran-2-one 4e were synthesized. The synthesized products were characterized on the basis of IR, 1H-NMR and 13C-NMR spectra. Compounds 4a-4e were screened for their antibacterial activity against S. Aureus, E. Coli and Klebsiella. Their antibacterial activity is examined by measuring the zones of inhibition around the disks impregnat
Keywords: Pyran-2-one, benzothiazole, condensation, antibacterial activity, zones of inhibition
This study is concerned with the synthesis and characterization of 4-thiazolidinone derivatives )3a-3h(. These compounds were prepared by reacting mercaptoacetic acid with the appropriate Schiff bases (imines) by heating at 50-60 °C in chloroform with moderate yields (51-75 %). The structures of these 4-thiazolidinone derivatives were established on the basis of the spectral studies using IR, 1H-NMR, 13C-NMR, 13C-NMR DEPT and MS.
Keywords: Thiazolidinones; imines; synthesis; NMR spectroscopy
The solubility of Alloxan in methanol, ethanol, ethane-1, 2-diol, water, acetone, and tetrahydrofuran was measured by gravimetric method over a temperature range (293.15 to 323.15) K at atmospheric pressure. The solubility increases non-linearly with temperature in all the studied solvents. Further, in protic solvents, solubility is maximum in methanol and minimum in ethane-1, 2 diol whereas in the selected nonprotic solvents, solubility is greater in tetrahydrofuran than in acetone. The experimental data were correlated with modified Apelblat and Buchowski-Ksiazczak equations. The calculated results show good agreement with the experimental data. Some thermodynamic parameters such as dissolution enthalpy, Gibb’s free energy, and entropy of mixing have also been calculated. The evaluated thermodynamic parameters are found to be positive. The positive enthalpy and Gibb’s free energy indicate endothermic and spontaneous dissolution of compounds. The positive entropy suggests entropy-driving dissolution process.
Keywords: alloxan; solubility; thermodynamic parameters; Apelblat and Buchowski-Ksiazczak models
An environmentally safer synthesis of 2-amino-tetrahydro-4H-chromenes derivatives using vitamin B1 was achieved by one pot synthesis. In this reaction condensation of various aromatic aldehydes, malononitrile and dimedone at room temperature without addition of any other catalyst has been done. The desired products can be separated directly from the reaction mixture with high purity. This synthetic method is inexpensive, efficient, as well as eco-friendly.
Keywords: Thiamine hydrochloride (VB1), green approach, tetrahydrobenzo[b]pyran derivatives
A new kind of 5-aryl-2-thioxoimidazolidin-4-ones synthesis by condensation of arylglyoxal hydrates with thiourea in acetic acid solution at room temperatures has been developed
Keywords: arylglyoxals, thiourea,5-aryl-2-thioxoimidazolidin-4-ones, synthesis, condensation
The FTIR study allowed to reveal that a hydrogen bond can arise in low - temperature films at 20 K between chloroform, bromoform and tetrachlorides of silicon and germanium, as well as a dihydrogen bond between chloroform and trichlorosilane. The general scheme of molecular interaction was simulated by ab initio calculation in terms of the DFT method. It was shown that the hydrogen atom of methane halides bound with the negatively charged chlorine atom of silicon or germanium tetrachloride, accompanied by transformation of their geometry from molecular symmetry Td to C3V.
Keywords: FTIR spectroscopy; low temperatures; hydrogen bond; haloforms; silicon; germanium tetrachloride; trichlorosilane
Materials and environmental chemistry
Heterogeneous photocatalysis using UV/VIS light or natural solar radiation as the energy source is one of the most efficient advanced oxidation processes (AOP) for the removal of chemical and bacterial pollutants from water. One of the least investigated oxides in this context, i.e. MnO2 and its combination MnO2/TiO2 are examined as potential photocatalysts for the removal of Indigo carmine (IC) dye pollutant from the water. The catalysts are characterized by XRD, FTIR, SEM, TEM, adsorption and surface area measurements. While MnO2 is very efficient for the decolorization of the dye, it is not effective enough for mineralization. MnO2 /TiO2 as the photocatalyst at the optimized ratio of 9:1 combines the advantages of both the oxides, i.e., rapid decolorization and efficient mineralization. Persulphate (S2O82-) enhances the degradation while H2O2 inhibits the same. The degradation is dependent on pH with higher degradation under extremely acidic conditions. The influence of dissolved salts/anions in the water on the degradation varies from ‘moderate inhibition' to ‘no effect' or even ‘enhancement' depending on the chemistry of the anion and reaction conditions. Effect of various parameters such as reaction time, substrate concentration, catalyst dosage, the presence of O2, recycling of the catalyst, etc. on the efficiency of degradation is investigated. The results are critically analyzed, and a tentative mechanism is proposed.
Keywords: anion effect; Indigo carmine dye; manganese dioxide; photocatalysis; titanium dioxide; persulphate
Gold nanoparticles were synthesized from chloroauric acid using the red wine of two types. The synthesis was carried out at room temperature. The optical absorption spectrum of the obtained gold nanoparticles was studied by using a UV-visible spectrophotometer, and the structure and particle sizes – by a transmission microscope. It was found that the geometric shapes of nanoparticles depended on the concentration of the working solution and the reducing agent. Nanoparticle size distribution histograms were plotted and assessed. The applications of obtained results were defined.
Keywords: gold nanoparticles, chloroauric acid, red wine, transmission electron microscopy, UV–Visible spectrophotometer