B. Narayana

Antimicrobial, analgesic, DPPH scavenging activities and molecular docking study of some 1,3,5-triaryl-2-pyrazolines

A series of 1,3,5-triaryl-2-pyrazolines 2a–g were synthesized by the reaction of 4,4′-disubstituted chalcone with phenyl hydrazine. All these compounds were characterized by NMR, IR and mass spectral and single crystal XRD data. All the synthesized products were screened for their in vitro antimicrobial, analgesic and antioxidant properties. The docking studies were carried out for these compounds against the active site of methionyl-tRNA synthetase (metRS). Some of the tested compounds exhibited significant antimicrobial, analgesic, DPPH scavenging activities and molecular binding.

FT-IR, molecular structure, first order hyperpolarizability, MEP, HOMO and LUMO analysis and NBO analysis of 4-[(3-acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid.

4-[(3-Acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid is synthesized and the structure of the compound was confirmed by IR, (1)H NMR and single crystal X-ray diffraction studies. FT-IR spectrum of 4-[(3-acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid was recorded and analyzed. The crystal structure is also described. The vibrational wavenumbers were computed using HF and DFT methods are assigned with the help of potential energy distribution analysis. The NH stretching frequency is red shifted in the IR spectrum with a strong intensity from the computed frequency, which indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The first hyperpolarizability and infrared intensities are also reported. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. Molecular electrostatic potential map was performed by the DFT method. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values.

1-[3,5-Bis(4-fluoro­phen­yl)-4,5-dihydro-1H-pyrazol-1-yl]ethanone

In the asymmetric unit of the title compound, C17H14F2N2O, there are three independent molecules (A, B and C) which differ slightly in the relative orientations of the two fluorophenyl rings. In molecules A and C one of the fluorophenyl rings is disordered over two positions, with occupancy ratios of 0.72 (2):0.28 (2) for molecule A and 0.67 (2):0.33 (2) for molecule C. The dihedral angle between the two fluorophenyl rings in the independent molecules lie in the range 70.3 (3)–84.0 (3)°. In the crystal structure, the molecules are linked via intermolecular C—H⋯O and C—H⋯F hydrogen bonds and π⋯π stacking interactions [centroid–centroid distance = 3.7508 (13) Å], forming a three-dimensional network.

Methyl 4,6-bis­(4-fluoro­phen­yl)-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate

The 3-cyclohexene units adopt envelope conformations in each of the two independent molecules that comprise the asymmetric unit of the title compound, C20H16F2O3. The dihedral angles between the two fluorophenyl rings are 79.7 (2) and 73.7 (2)° in the two molecules. In one of the molecules, two C—H groups of the cyclohexene ring are disordered over two sets of sites in a 0.818 (13):0.182 (13) ratio, the major and minor components corresponding to the two enantiomeric forms of the molecule. Weak intermolecular C—H⋯O interactions help to stabilize the crystal structure.

Synthesis and characterization of some chalcones and their cyclohexenone derivatives

A series of chalcones and their derivatives have been synthesized. Chalcones, 1-(1,3-benzodioxol-5-yl)-3-(aryl)-prop-2-en-1-ones were prepared by the aldol condensation of 1-(1,3-benzodioxol-5-yl)ethanones and aryl aldehydes. Based-catalyzed condensation of 1-(1,3-benzodioxol-5-yl)-3-(aryl)prop-2-en-1-ones with ethyl acetoacetate yields corresponding ethyl 4-(1,3-benzodioxol-5-yl)-6-(aryl)-2-oxocyclohex-3-ene-1-carboxylates. Some of the synthesized chalcones were reported in the literature; the newly synthesized compounds were characterized by single crystal X-ray studies, IR, 1H-NMR and LCMS mass spectral analysis.

Molecular structure, FT-IR, NBO, HOMO and LUMO, MEP and first order hyperpolarizability of (2E)-1-(2,4-Dichlorophenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one by HF and density functional methods.

(2E)-1-(2,4-Dichlorophenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one is synthesized by using 2,4-dichloroacetophenone and 3,4,5-trimethoxybenzaldehyde in ethanol. The structure of the compound was confirmed by IR and single crystal X-ray diffraction studies. FT-IR spectrum of (2E)-1-(2,4-dichloro-phenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one was recorded and analyzed. The crystal structure is also described. The vibrational wavenumbers were computed using HF and DFT methods and are assigned with the help of potential energy distribution method. The first hyperpolarizability and infrared intensities are also reported. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. MEP was performed by the DFT method. From the MEP map of the title molecule, negative region is mainly localized over the electronegative oxygen atoms, in the carbonyl group and the oxygen atom O4 of the methoxy group and the maximum positive region is localized on the phenyl rings.

3,5-Bis(4-fluorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole

In the title compound, C21H16F2N2, the dihedral angle between the fluorophenyl groups is 66.34 (8)°, and the dihedral angle between the envelope-configured pyrazole group (N/N/C/C/C) and the benzene ring is 11.50 (9)°. The dihedral angles between the benzene and the two fluoro-substituted phenyl groups are 77.7 (6) and 16.7 (5)°. Weak C—H⋯π interactions contribute to the stability of the crystal structure.

3,5-Bis(4-fluoro-phen-yl)-4,5-dihydro-1H-pyrazole-1-carbaldehyde.

In the title molecule, C16H12F2N2O, the pyrazole ring adopts a slight envelope conformation with the methylene C atom deviating by 0.114 (3) Å from the mean plane of the other four atoms [maximum deviation = 0.021 (3) Å]. The dihedral angles between the four essentially planar atoms of the pyrazole ring and the fluoro-substituted benzene rings are 2.6 (2) and 82.2 (2)°. The dihedral angle between the two benzene rings is 83.7 (2)°. The crystal packing is stabilized by weak intermolecular C—H⋯O hydrogen bonds.

A new system for the spectrophotometric determination of trace amounts of nitrite in environmental samples

A selective and rapid spectrophotometric method for the determination of nitrite is presented. It is based on the reaction of nitrite with p-nitroaniline in acid medium to form diazonium ion, which is coupled with ethoxyethylenemaleic ester or ethylcyanoacetate in basic medium to form azo dyes, showing absorption maxima at 439 and 465 nm respectively. The method obeys Beers law in the concentration range of 0.5-16 µg mL-1 of nitrite with ethoxyethylenemaleic ester and 0.2-18 µg mL-1 of nitrite with ethylcyanoacetate. The molar absorptivity and Sandells sensitivity of p-nitroaniline-ethoxyethylenemaleic ester and p-nitroaniline-ethylcyanoacetate azo dyes are 5.04 X 104 L mol-1cm-1, 0.98 X 10-2 µg cm-2 and 1.21 X 104 L mol-1 cm-1, 0.98 X 10-2 µg cm-2 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The method was successfully applied to the determination of nitrite in various water samples and soil samples.

3,5-Bis(4-bromo­phen­yl)-1-phenyl-4,5-dihydro-1H-pyrazole

In the title compound, C21H16Br2N2, the central pyrazole ring adopts an flattened envelope conformation, with the stereogenic C atom in the flap position. The deviations from planarity for this ring are relatively minor (r.m.s. deviation = 0.045 Å) and the dihedral angles formed with the N- and Cimine-bound benzene rings are 7.73 (13) and 11.00 (13)°, respectively. By contrast, the benzene ring bound at the chiral C atom is almost orthogonal to the rest of the molecule; the dihedral angle formed between this ring and the pyrazole ring is 79.53 (13)°. In the crystal, the packing is stabilized by C—H⋯N and C—H⋯Br interactions.