Asian Journal of Green Chemistry

Abstract In this research, a new method that used graphene oxide (GO) nanosheets melamine butanedioic acid (GO-MB) composites and derivation of poly (Styrene–alternative-maleic anhydride) (SMA), (SMA + melamine-butanedioic acid) (SMA-MB) is presented as sorbents for the elimination of zinc(II) ions from aqueous solutions. The adsorbents have the sufficiency to adsorb the zinc(II) ions. Through immobilizing the melamine-butanedioic acid onto GO nanosheets and SMA-MB, the desired composite was synthesized and identified by field emission scanning electron microscopy (FE-SEM) and fourier transform infrared (FT-IR) spectroscopy techniques. Some experimental parameters including, pH, concentration of the aqueous solution of zinc(II) ions, the content of the zinc(II) ions, the grapheme oxide-melamine-butanedioic acid, and SMA-MB were optimized. The results showed that, the adsorbents were matched with langmuir isotherm. It was also revealed that the uptake efficiency of zinc(II) ions considerably increased after immobilization of melamine-butanedioic acid on the GO nanosheets and SMA. These adsorbents were also shown to be very suitable to remove the zinc(II) ions from aqueous solutions.

Abstract A facile, convenient, efficient, and high-yielding diastereoselective synthesis of a novel fused dihydro-1H-furo[2,3-c]pyrazole by a one-pot four-component reaction of β-keto ester, hydrazine, aromatic aldehyde and pyridinium salt in the presence of [bmIm]OH ionic liquid medium provided with excellent yields. Three new bonds (two C‒C and one C‒O), and two stereo centres are generated in a single operation. Low cost, short reaction time, excellent yield, operational simplicity, and more importantly the purification of the compounds by a non-chromatographic method make this process very significant for academic research and practical applications.

Abstract In this study, the diterpen compounds present in the ethyl acetate fraction of stem bark of Boswellia papyrifera grown in Sudan were investigated using gas chromatography-mass spectrometry (GC-MS), based upon interpretation of the mass spectra fragmentation data, matching their mass spectra with NIST databases, and by comparison of the mass spectra obtained with those reference compounds published in literature.  A total of nine diterpenes were identified as m-camphorene 1, pimaradiene 2, verticilla-4(20),7,11-triene 3, serratol 4, incensole 5, incensyl acetate 6, duva-3,9,13-trien-1α-ol-5,8-oxide-1-acetate 7, incensole oxide 8, incensole oxide acetate 9 respectively. Among them compound 1, 2, 4 and 7 were reported here for the first time from this plant.

Abstract Azides are the precursors of two important derivatives in synthetic organic chemistry. Achiral amines are not as demandable as that of chiral ones. Chiral amines and diamines have versatile uses in enantioselective reactions. Both simple and amino alcohols were undergone smooth azidation reaction in the mixture of NaN₃, H₂SO₄ in toluene solvent and afforded good to charming yields. Importantly, optical purity of some chiral amino alcohols was reserved during azidation reaction. This is an efficient method to synthesise new azides for the fabrication of new organocatalyst which is friendly to the environment.

Abstract Rhizophora mucronata is a species of mangrove widely distributed in Indian mangrove forest. It seems to be more tolerant of inundation than other mangrove species and often forms an evergreen fringe to mangrove areas. In present study, the methanolic extract of different parts of Rhizophora mucronata, their antioxidant properties along with primary, secondary metabolites and proximate composition, were tested. Better antioxidant activity was gained by methanolic extract of leaf than root and bark extract. Antioxidant potential of the extracts was analyzed as contents of total phenols and flavonoids; radical scavenging activity by the DPPH methods, NO and H₂O₂ and primary and secondary metabolites assay and the results of antioxidative activities from the R. mucronata plant. The total content of phenols and flavonoids in the methanol extracts of the studied species positively correlated with their antioxidant properties, confirmed their major role in antioxidant activity of these R. mucronata.

Abstract The biological synthesis of NPs using plant extracts plays an important role in the field of nanotechnology. In this study, magnetite nanoparticles (Fe₃O₄ NPs) were synthesized using a rapid, single step and completely green biosynthetic method by reducing ferric chloride hexahydrate and ferrous chloride tetrahydrate solution with Persea Americana leaf aqueous extract containing flavonoids and phenolic compounds as the main factor which acts as the reducing agent and efficient stabilizer. The structural and properties of the Fe₃O₄ NPs were investigated by UV-visible spectroscopy, fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). Moreover, the antimicrobial properties of Fe₃O₄ NPs were confirmed using the disk diffusion test and minimum inhibitory concentration and minimum bactericidal concentration on Staphylococcus aureus and Escherichia coli. The obtained results of disk diffusion test indicated that Fe₃O₄ NPs prevented the bacterial growth. Additionally, the obtained results demonstrated that the minimum inhibitory concentration and minimum bactericidal concentration of Fe₃O₄ NPs for Staphylococcus  aureus were 12.5 mg/mLandfor Escherichia coli were  6.25 mg/mL. The findings of this study showed that Fe₃O₄ NPs can be used to inhibit the mentioned bacteria.

Abstract This study reports the synthesis, characterization and catalytic properties of a novel supported catalyst on the basis of nickel acetate hydrate (NiOAC) immobilized on graphene oxide (GO) modified polyethylene glycol (PEG). The catalyst was characterized by scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), furrier transforms infrared spectroscopy (FT-IR) and diffuse reluctance spectroscopy (DRS). It showed a high activity in the green oxidation of thioanisole as a model substrate to sulfoxide product at ambient temperature and presurre. To establish the general applicability of the process, various sulfides were subjected to the oxidation system using the synthesized catalyst. The reactivities of the sulfur compounds were influenced by two main factors, i.e., the electron density on the S atom and the steric hindrance of the sulfur compound. In addition, ethanol was selected as a green solvent for this procedure. The effects of the main process variables including H₂O₂ amount (mmol), reaction time (min) and catalyst amount (mg) were analyzed by response surface methodology (RSM) based on the central composite design (CCD). The optimal condition for conversion of thioanisole was found to be O/S ratio 3.4, reaction time 31 min for 21 mg of catalyst amount.

Abstract Green synthesis of nanoparticles has received great attention from scientists due to their undeniable applications in all field of science. In this study, an eco-friendly and fast approach is reported for the preparation of silver nanoparticle (Ag NPs) using Spartium junceum flower extract, as a reductant and stabilizer agent, from aqueous solution of silver nitrate. The biosynthesis of silver nanoparticles was optimized by investigating the reaction parameters including:  pH, temperature, concentration of plant extract and interaction time. The silver nanoparticles were characterized by UV-vis, fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. Also, the biosynthesis of Ag NPs was confirmed by UV-vis spectroscopy through the presence of a characteristic surface plasmon resonance (SPR) band for Ag NPs at l_max=420 nm. The synthesized nanoparticles were crystalline in nature, nearly spherical in shape with 15-25 nm range of sizes.

Abstract Lignocellulosic biomass contains polymers of cellulose, hemicellulose, and lignin, bound together in a complex structure. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. These factors hindering access to sugars contained in lignocelluloses are summed up as “recalcitrance”. As a result, pretreatment is required to allow liberal access to the full contents of lignocellulosic biomass. Production of value added co-products along with biofuels through integrated biorefinery processes create the need for selectivity during pretreatment. Pretreatment is an important tool for biomass-to-biofuels conversion processes and is the subject of this review article. The major target of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and enhance the degree of hydrolysis. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, for lignocellulosic biomasses such as woods, grasses, corn, rice straw, etc. In this review, we discuss the ionic liquids (ILs) pretreatment method in biorefinery and the recent literature that has reported on the use of these so called green solvents for pretreatment of various lignocellulosic biomasses, ionic liquids have recently become very popular solvents for the dissolution of biomass due to their unique features as compared to conventional solvents.