Classical and advanced chemical sciences
Totally twelve ((2-hydroxy-1-naphthyl))(3-(substituted phenyl)bicyclo [2.2.1]hept-5-ene-2-yl)methanones have been synthesized by fly-ash catalyzed water-mediated Diels-Alder [4+2] cycloaddition reaction. The synthesized bicyclic ketones were characterized by their physical constants, analytical and spectroscopic data. The antimicrobial and antioxidant activities of these bicyclic methanones were evaluated using Bauer-Kirby disc diffusion and diphenyl picrylhydrazyl(DPPH) radical scavenging technique. Most of the bicyclic methanones showed good antibacterial and antifungal activities against their microbial strains. The hydroxy- and methoxy- substituted methanones shows significant antioxidant activity.
Keywords: water-mediated Diels-Alder reaction; 2-hydroxy-1-naphthyl chalcones; cyclopentadiene; IR spectra; NMR spectra; antimicrobial activity; antioxidant activity.
Synthesis of new 1-(4-substituted phenylimino)-1-(4-hydroxyphenyl)propanes has been done successfully. These Schiff bases were converted to 3-ethyl-3(4-hydroxyphenyl)-2-(4-substituted phenyl)isothiazolidin-4-one and 3-chloro-1-(4-substituted phenyl)-4-ethyl-(4-hydroxyphenyl)azetidin-2-one derivatives with thioglycolic acid and chloroacetyl chloride/Et3N mixture in 1,4-dioxane, respectively. All the synthesized compounds were screened for biological activities.
Keywords: Schiff bases, 4-Thiazolidinone, 2-Azetidinone, Antibacterial activity
The influence of in situ synthesized biocomposite consisted of Phragmites australis (Pha) - common reed and emeraldine base (Emb) on the removal of copper ion from aqueous media is discussed. The biocomposites were prepared with two different ratios of common reed/aniline (samples Pha/Emb1 and Pha/Emb2, respectively. Physicochemical parameters such as initial copper ion concentration, composite dosage and contact time between the composites and Cu(II) ions in aqueous solution were studied. An assessment of the equilibrium and the kinetics of sorption of copper ions has been made. Removal efficiency of 99.6 % was achieved with Pha/Emb1 and 91.9 % with Pha/Emb2, respectively. The experimental results were fitted to the isotherms of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. It was established that the Langmuir isotherm is more suitable for the case of emeraldine base and for composite Pha/Emb1, while the Dubinin-Radushkevich isotherm is more suitable for the case of Pha/Emb2 (with higher content of common reed). The influence of the plant quantity in the biocomposite is important for the mechanism of Cu2+ removal. Physical adsorption and ion exchange are dominant in the case of Pha/Emb1, and Emb, while in the case of Pha/Emb2 the chemical interaction is predominant. The kinetics of Cu(II) adsorption onto biocomposites followed pseudo-second-order model.
Keywords: In situ polymerization, polyaniline, Phragmites australis, copper ions adsorption
Ni (15% w/w) supported on alumina, silica, and titania (P-25, anatase and rutile phases) have been investigated for the liquid phase hydrogenation of cinnamaldehyde. XRD, TPR and XPS data (binding energy shifts for Ni2p) indicate metal-support interactions in all supported catalysts. Weaker binding of H2 on Ni/TiO2 (H2-TPD) improves activity. Ni/TiO2 phases display higher cinnamaldehyde conversion and selectivity to cinnamyl alcohol compared to the catalysts supported on alumina and silica. Amongst the three polymorphs of titania, the maximum activity, and selectivity displayed by Ni/ TiO2-P-25, is attributed to the active Ni crystallites located at the interface between anatase and rutile phases in titania P-25 matrix (HRTEM). Though Ni crystallites on alumina and silica are relatively smaller (compared to those on the three TiO2 phases) in size, their activity vis-à-vis for those supported on titania phases is less, implying that factors other than crystallite size influence the performance.
Keywords: Cinnamaldehyde; hydrogenation; role of supports; polymorphs of titania; nickel at interface
Materials and environmental chemistry
green approach has been developed for the synthesis of nanocrystalline zinc oxide (ZnO) with the aid of room-temperature synthesized ionic liquids (RTIL's) as crystal growth modifiers by low-temperature precipitation technique. The role of RTIL's (propylammonium acetate (PAA), propylammonium formate (PAF), 3-hydroxy propylammonium acetate (3 HPAA), 3-hydroxy propylammonium formate (3HPAF) and their concentration effect on the particle size is studied in this protocol. The formed nanoparticles are characterized by XRD, TEM, FT-IR and UV-DRS. XRD spectra of nanoparticles exhibit typical diffraction peaks of hexagonal phase with wurtzite ZnO structure corresponding to JCPDS 36-1451. TEM results revealed that spherical nanoparticles obtained with an average particle size in the range of 5-20 nm. UV-Vis-DRS spectra of the ZnO nanoparticles shows blue shift compared to the bulk ZnO, attributed to quantum confinement effect.
Keywords: ZnO, Ionic liquids, XRD, TEM, FT-IR, UV-DRS and Particle Analyzer
Industrial and engineering chemistry, biotechnology
Diphenylamine (DPA) is photocatalytically oxidized to N-phenyl-p-benzoquinone imine (PBQ) on the surface of CdO in ethanol under UV light as well as natural sunlight. The variation of the rate of PBQ formation on CdO surface with (i) [DPA] and (ii) airflow rate conforms to the Langmuir-Hinshelwood kinetic law. The catalyzed PBQ formation increases with the catalyst loading and light intensity. UV-C light is more effective in catalyzed PBQ formation than UV-A light, and the catalyst is reusable. The reaction mechanism on the illuminated CdO surface is discussed, and the kinetic constants deduced. V2O5 and ZnS enhance the photocatalyzed formation of PBQ.
Keywords: Semiconductor; photocatalysis; sunlight; band gap; interparticle charge transfer
An attempt has been made to enhance the photocatalytic activity of bismuth ferrite by doping it with cobalt, to prepare a catalyst to use in wide pH range for the photodegradation of Evans blue dye. The progress of the reaction has been monitored spectrophotometrically by measuring the absorbance of the reaction mixture at definite time intervals. Different parameters such as pH, the concentration of dye, amount of semiconductor and light intensity were varied to achieve the optimum rate of photodegradation. The results show that doping of bismuth ferrite by cobalt increases the rate of photocatalytic degradation due to narrowing of the band gap. Undoped bismuth ferrite has the highest catalytic activity in basic while the Co-doped catalyst in acidic medium. A tentative mechanism for the reaction has been proposed
Keywords: Evans blue, Bismuth ferrite, Co-doped bismuth ferrite, Heterogeneous, Photocatalytic degradation