European Journal of Chemistry

A study on the structure of methyl salicylate is reported using quantum mechanical calculations, molecular dynamics simulations, vibrational spectroscopy and microwave dielectric relaxation spectroscopy tools. The reported results show that a strong intramolecular hydrogen bonding is developed between the hydroxyl hydrogen and carbonyl oxygen. This intramolecular interaction is maintained in gas and liquid phases and even when diluted in inert solvents. Interaction between neighbour molecules is developed through dipolar interactions, and thus, intermolecular hydrogen bonding should be discarded for pure liquid methyl salicylate. The interaction between neighbour methyl salicylate molecules do not lead to remarkable changes in the intramolecular hydrogen bonding.

7-(4-Chloro/3-nitrophenyl)-8-[5,6-diphenyl-4-(1,3-thiazol-2-yl)-1,4-dihydro-1,2,4-triazin-3-yl]-5-oxo-1,5-dihydro[1,2,4]triazolo[1,5-a]pyridine-6-carbonitrile (6a, b) was utilized as a key intermediate for the target polyheterocyclic systems. Reactions of 6a, b with halocarbonyl reagents followed by heterocyclization with bi-nitrogen nucleophiles gave some new nitrogen heterocycles (7-13). Structures of the new compounds were established by elemental analyses and spectral data. The synthesized compounds were screened for their antimicrobial activity.

The FT-IR and FT-Raman spectra of 1,3-diphenyl thiourea were recorded and analyzed. The vibrational wavenumbers were examined theoretically with the aid of the Gaussian03 package of programs using the HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels of theory. The data obtained from vibrational wavenumber calculations are used to assign vibrational bands obtained in IR and Raman spectroscopy of the studied molecule. The first hyperpolarizabililty, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non-linear optics. The geometrical parameters of the title compound are in agreement with the values of similar structures. The changes in the C-N bond lengths suggest an extended π-electron delocalization over the thiourea moiety which is responsible for the non-linearity of the molecule.

A new three dimensional proton transfer compound, (tataH)₂(citH).2H₂O (I) was synthesized from the reaction of citric acid (citH₃), and 2,4,6-triamino-1,3,5-triazine (tata). The characterization was performed using elemental analysis, IR spectroscopy, and single crystal X-ray structure determination. The crystal structure of the title compound consists of bis-2,4,6-triamino-1,3,5-triazin-1-ium cations, hydrogen citrate, and lattice water molecules. Intermolecular O-H•••O, N-H•••O, and N-H•••N hydrogen bonding interactions stabilize the crystal structure. The hydrogen bonds distances range from of 1.781 to 2.088 Å. The π-π stacking (centroid-centroid ranges 3.410-3.504 Å) between two aromatic rings of tata moieties can play an essential role in the creation and stabilization of the title crystalline network.

Recently we have calculated the electronegativity of 103 elements of the periodic table relying upon the basic approach of Allred and Rochow. We carefully allayed the dimensional mismatch seemingly prevalent in all previous calculations so that the computed electronegativity is in its proper force dimension. Since the electronegativity is neither a physical observable nor a quantum mechanically determinable quantity, there is no bench-mark to perform any validity test of any scale of electronegativity. The descriptors of the real world such as charge distribution, bond energies, bond polarities and the dipole moments, force constants, atomic polar tensor and internuclear distances can be conceived in terms of electronegativity. Since the scale of Allred and Rochow is extremely popular among the scales of electronegativity, we have performed a validity test of the newly modified scale by calculating the dipole moments of as many as 48 molecules of widely diverse nature using the electronegativity values computed by us. The comparative study of computed dipole moments vis-à-vis the available experimental dipole moments of the corresponding molecules reveals that the present scale of electronegativity can be used realistically in representing the physical descriptors like charge distribution and dipole moments of molecules.

Aluminon has been investigated for the separation of iron(III) by flotation technique. This reagent formed a 1:1 stable complex in aqueous solution. An intense violet layer is formed after flotation using oleic acid (HOL). A highly selective and sensitive spectrophotometric procedure is proposed for the determination of Fe(III) after overcoming all interferences. Preliminary studies show the possibility of forming a complex with Fe(II) to an extremely low extent. Trials have been carried out to separate Fe(II) and Fe(III) using NH₄SCN or NaF. To prevent the oxidation of Fe(II), NaBH₄ is used.  The separation of Fe(III) and Fe(II) can be achieved using 0.6 mg L^-1 NaBH₄.  The flotation- determination method was carried out at pH 2-3. The formation constant is 1.3×10⁷ L mol^-1 with molar absorptivity of 0.2×10⁵ L mol^-1 cm^-1 and detection limit of 5×10^-6 mol L^-1. The effect of foreign ions is avoided using excess aluminon and 0.5 mg L^-1 NaBH₄. The proposed procedure was applied to synthetic mixtures [Fe(III) + Fe(II)], Fe(III) and some cations, wastes of power stations, simulated samples and real ores.

3-(1-Ethyl-4-hydroxy-2-oxo-2(1H)-quinolin-3-yl)-3-oxopropanoic acid (2) has been synthesized. The chemical behaviour of β-ketoacid 2 was studied towards condensation reactions with salicylaldelyde, 2-hydroxy-1-naphthaldehyde, 1-phenyl-4-hydroxy-2-oxo-quinoline-3-carboxaldehyde, 2-hydroxy-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxalde-hyde, 2-amino-3-formylchromone and its 8-allyl analog, 3-cyanochromone and its 8-allyl analog. Structures of the newly synthesized products have been deduced from their elemental analysis and spectral data.

Nickel and copper metal complexes of N-(R-carbamothioyl)-4-nitrobenzamide (R = diphenyl and ethylbutyl) were synthesized and characterized by IR, ¹H NMR, mass spectrometry and elemental analysis. The spectroscopic data are consistent with the ligand and the metal complexes containing two O and S chelated ligands. N-(diphenylcarbamothioyl)-4-nitrobenzamide, HL¹, was characterized by a single crystal X-ray diffraction study. It crystallizes in the triclinic space group P  with unit cell dimensions of a = 6.8044(4) Å, b = 10.0113(6) Å, c = 13.2365(8) Å, α = 6.8044(4) °, β = 78.171(4) °, γ = 13.2365(8)°, V = 882.43(9) ų. The ligands coordinate as bidentates yielding essentially neutral complexes of the type [ML₂]. The ligands and complexes were screened for their in vitro antibacterial activities and comparatively the complexes showed greater antibacterial efficacy than the thiourea derivative ligands.

Baicalein, a trihydroxy flavone from the bark of Terminalia bellerica was identified as a natural colorant. The potential of the natural color component on silk yarn was tested. Its properties of color fastness with regard to light, washing and crocking were investigated and found to be satisfactory. Thermodynamic parameters were evaluated. The positive value of enthalpy of dyeing suggests the endothermic nature of dyeing and the negative entropy implies that the dye molecules are orderly arranged on silk. The positive value of free energy confirms the affinity between the dye molecules and the protein content of silk. Further, adsorption studies were carried out to determine the best fit isotherm model for the present dyeing system. The Langmuir isotherm model fitted the experimental data very well with a relatively high regression coefficient compared to the Freundlich and Tempkin-Pyzhev isotherm models. In conclusion, the Terminalia bellerica bark can be used as a potential source of natural dye for silk.

Cerium phosphate, CePO₄, nanoparticles with hexagonal or monoclinic phase was synthesized by the reaction between Ce(SO₄)₂.4H₂O and two different phosphate sources, H₃PO₄ and Na₂HPO₄. The obtained gel was dried and calcined at different temperatures (200, 400, and 800 ^оC). The effects of the precursor materials and the calcination temperatures on the produced phases were studied. Both X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to follow the changes in the phase structure for the produced samples. The thermal behaviour of the as prepared samples was studied by using differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA). The morphology, crystallinity and particle size of the produced samples as prepared and calcinated were characterized by transmission electron microscope (TEM). The analysis of TEM results indicated that CePO₄ was prepared in nano-sized particles.

A sensitive and selective preconcentration method has been developed for the determination of trace amounts of lead and cadmium ions by using naphthalene-methyltrioctylammonium chloride as an adsorbent. Lead and cadmium ions were retained by the adsorbent in the minicolumn as PbI₄^2- and CdI₄^2-, respectively. The column was washed by 5 mL of 2 mol L^-1 nitric acid solution to elute the adsorbed cations. The collected eluents then were determined by flame atomic absorption spectrometry (FAAS). Potential factors affecting on the recovery of the analytes were investigated. Meanwhile optimum conditions were established. The preconcentration factor for lead (II) and cadmium (II) have been 300 and 100, respectively. The calibration curves were linear in the range of 3 to 100 ng mL^-1 for Pb²⁺ and in the range of 1 to 100 ng mL^-1 for Cd²⁺, in the original water samples. The detection limits for Pb²⁺ and Cd²⁺ are 0.42 and 0.072 ng mL^-1 respectively. On the other hand, the relative standard deviation (RSD) for 11 replicate measurements of 20 ng mL^-1 Pb²⁺ and Cd²⁺ were 2.2% and 1.4% in the initial solution respectively (n=11). The developed method was successfully applied for the determination of trace Pb²⁺ and Cd²⁺ ions in a variety of water samples.

This article presents our research concerning the synthesis of new thiophene-thiourea derivatives (1-12) and their pharmacological properties. These novel thiophene-thiourea derivatives were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopy, mass spectrometry and elemental analysis. The crystal structure of N,N-diphenyl-N'-(thiophene-2-carbonyl)-thiourea was determined from single crystal X-ray diffraction data. It crystallizes in the monoclinic space group P2₁ with unit cell dimensions of a=11.7469(5) Å, b=6.0849(2) Å, c=12.5792(6) Å, β= 117.736(7) ° and V = 795.8(6) ų. The mass fragmentation pattern has also been discussed. The synthesized compounds were screened for their in vitro antifungal activities against the standard strains: C. Albicans, C. Glabrata, and C. Tropicalis. The compounds N-thiophene-N',N'-bis(dimethyl-phosphinoylmethyl)thiourea, N-[(4-nitro-1H-imidazol-2-yl)carbamothioyl]thiophene-2-carboxamide and N,N-diethyl-N'-(thiophene-2-carbonyl)-thiourea showed significant antifungal activities against microbial species.

A simple and highly efficient protocol for the synthesis of quinoxaline derivatives from various ortho-phenylenediamines with α-halo ketones under catalyst free conditions is reported by using polyethylene glycol (PEG-400) as an efficient recyclable medium without using any organic co-solvent or additive. This protocol gives wide range of quinoxaline derivatives with high yields.

3-cyano-2(1H)-pyridinones and their 2-imino analogues have been synthesized in good yields via a one-pot multi-component reaction of 3,4-dimethoxyacetophenone, malononitrile or ethylcyanoacetate, ammonium acetate and various aldehydes in the presence of  1,4-diaza-bicyclo[2,2,2]octane (DABCO) in ethanol. DABCO has been widely used as a catalyst for the organic reactions and we selected it as an efficient catalyst to synthesis of 3-cyano-pyridines. All products were characterized by melting point, IR, ¹H NMR and GC/MS studies.

Orientation of heterocyclization reactions of functionalized 1,2,4-triazines were studied by effect of substituents in 1,2,4-triazine moieties, type of the solvent used in the reaction and the temperature effect. Also, it was found that cyclization process depended mainly on the chemoselective and regioselectivity states of the parent substrate as well as preferring cite of ring closure.