Reaction In Presence Research Articles

A comprehensive review on catalytic O-alkylation of phenol and hydroquinone

ABSTRACT The alkylation process involves two competitive paths of O- and C-alkylation and achieving better selectivity for desired products is a very challenging problem. The development of new process for synthesis of O-methylated products of phenol and dihydric phenols is a subject of high industrial and academic interest. Alkyl phenyl ethers, especially anisole and 4-methoxyphenol, have captivated significant interest due to their increasing applications in pharmaceutical industries. The main emphasis of the present review is to explore the recent development in two catalytic O-alkylation processes. The first process is O-methylation of phenol into anisole and another is selective mono O-methylation of hydroquinone into 4-methoxyphenol. The present article covers O-alkylation methods with methanol and dimethyl carbonate as alkylating agent over various acidic and basic catalytic systems. The catalyst systems analyzed involves Bronsted and Lewis acidic and basic ionic liquids, conventional acids, metal oxides, solid acid and basic catalysts, hydrotalcites, various zeolites and heteropolyacids. The mechanistic behavior of alkylation reactions in presence of different catalytic system is reviewed critically which is important to design new and/or modified catalyst in order to maximize the yield of desired product. Additionally, an influence of reaction parameters, role of catalyst and their active sites on product distribution is described. The review paper gives useful insight for researchers in the field of catalysis and reaction engineering of alkylation reactions. Understandings of the reaction pathways will help in developing reliable kinetic models necessary for process scale-up to industrial scale reactor system.

Stable, but still reactive – investigations on the effects of Lewis acid binding on copper nitrene intermediates

AbstractCopper nitrenes are proposed as reactive intermediates in a number of copper mediated aziridination and amination reactions. However, the isolation and characterization of such intermediates have proved challenging because of their transient nature. One successful approach for the stabilization of the copper‐nitrene cores is the employment of a redox innocent Lewis acid (LA) like Sc3+. We herein report the stabilization of two transient copper nitrene species 3 and 4 in the absence of LAs by employing electronegative −CF3 and −NO2 groups in the nitrene substituent. Detailed investigations of the spectroscopic properties of 3 and 4 by theoretical and experimental methods, and a comparison of their reactivities in presence and absence of LAs provide some vital insights into the effect of LAs on the geometric and electronic structures of the copper nitrenes.

Multicomponent Wittig Reaction As Simple and Efficient Method for Synthesis of New Tri Substituted Pyrroles Under Catalytic Phosphine Mediated

The key precursor for the synthesis of the tittle system are an active hetero chalcones (1&2) which reacted with sulfathiazole to afford α-β-unsaturated Schiff bases represented by compounds 4-( (z)-(E)-2,3,5-tri aryl allylidene amino)-N-(thiazole-2-yl) benzene sulfonamide (3&4). The lase one was under went multicomponent witting reaction in presence of acid chloride and tri phenyl phosphine in basic media from tri ethyl amine to afford the substituted pyrrole named 4-(2,3,5-tri aryl-1H-pyrrole-1-yl)-N-(thiazole-2-yl) benzene sulfonamide (5-11).The structure of prepared compounds were determined by the available physical and spectral methods M.P. ,T.L.C , U.V , FT-IR & 1H-NMR

Development and Validation of Reverse-phase High-performance Liquid Chromatography Method for Novel Synthetic Pyridine Derivative

The study was focused toward synthesis, characterization and quantification of Pyridine derivative by Reverse Phase High Performance Liquid Chromatography method. The synthesis of novel pyridine derivative was carried out by condensation reaction in presence of inert catalyst K2CO3 and THF solvent. Characterization was done by I.R, 1H-NMR,and HPLC. Based on the spectral data, the structure of novel pyridine derivative was characterized as 5 - (4 - Substituted amino) - 3- Nitrobenzene - 1 - Sulfonyl) - 4, 5, 6, 7 –Tetrahydrothieno[3, 2 - C] Pyridine The method validation including precision, accuracy, LOD, robustness, Linearity, and range was developed as per ICH guideline through an efficient isocratic RP-HPLC.It was determined that the above procedure is specified, accurate, precise, robust, and sturdy.

Density functional studies of the catalytic oxidation of CO using small aurocarbons

The catalytic activity of small aurocarbons C4H3Au and C4Au4 for the transformation of CO to CO2 is investigated using the dispersion corrected density functional theoretical method. The activation energy barrier 1.54 eV for the reaction in presence of C4H3Au is reduced to 1.38 eV on substituting all the hydrogen atoms by gold atoms. Effect of pre-occupation of CO and O2 on the mechanism and energetics of the reaction is examined. The study revealed that the pre-adsorption of CO at all the gold sites of C4Au4 significantly reduces the energy barrier for the reaction.

Techno-economic feasibility of industrial production of biofuels by glycerol etherification reaction with isobutene or tert-butyl alcohol assisted by vapor-permeation membrane

A preliminary evaluation of the techno-economic feasibility of an industrial glycerol etherification process for bio-additives production has been carried out. The attention has been focused on the etherification reaction in presence of isobutylene (IB) or tert-butanol (TBA) in a batch reactor, catalyzed by an optimized heterogeneous system. Specifically, the Hyflon-based catalyst resulted more efficient and selective to desired products than commercial resin, limiting the competitive reactions of IB oligomerization and byproduct formation. In case of IB, a mixture of poly-ethers, suitable as oxygenated additives for diesel engines, containing very low amount of mono-tert-butylethers (<2wt.%) was obtained in a single step. This allowed a simplification of the process without the need of separation units and a lower production cost with respect to other reference processes. When TBA was used and water was formed as byproduct, a permeoselective membrane was exploited improving the glycerol conversion and enhancing the poly-ethers productivity by continuous water removal. In fact, very high poly-ethers yield (>85%) was achieved under optimized reaction conditions. The analysis of the whole process demonstrated the techno-economic sustainability of the proposed routes, leading to a production price of glycerol poly-ethers of 1,14USD/kg and 2,38USD/kg, by using IB or TBA respectively.

Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable Ti0.97Pd0.03O1.97 Catalyst

Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti0.97Pd0.03O1.97 catalyst supports C–C bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 different aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach for the cross-coupling reaction is also attempted.

Isolation, characterization and semi-synthesis of natural products dimeric amide alkaloids

Isolation, characterization and semi-synthesis of natural products dimeric amide alkaloids

Reduction of p-nitrophenol to p-aminophenol using an efficient, cheap and simple technique to prepare spinel ferrites: A comparative study

A successful reduction of p-nitrophenol was carried out on the surface of novel CuFe2O4. Copper ferrite (CuFe2O4) nanoparticles were prepared via simple co-precipitation reaction in presence of a capping agent. The prepared nanoparticles was investigated by DSC (Differential Scanning Calorimeter) and the crystalline structure and size were estimated by XRD (X-Ray diffraction). The experimental results have pointed out the high catalytic activity towards the reduction of p-nitrophenol to p-aminophenol (important intermediate for paracetamol and analgesic drugs) which improved greatly by using polymer as capping agent, where it exhibited several advantages such as low-cost, stability and rapid separation.

Photoenhanced performance of Cobalt-intercalated 2-D manganese oxide sheets for rechargeable zinc–air batteries

Conversion and storage of renewable energy is an important step towards the sustainable future. In this work, we have combined photoconversion of solar energy and Zn–air batteries in a single device which could be an effective strategy for augmenting energy conversion and storage. We report the synthesis of inexpensive cobalt-doped 2D δ-MnO2 nanosheets by one-pot hydrothermal method. Spectroscopic and microscopic characterizations prove both in-plane and interplanar doping of cobalt in δ-MnO2 structure. The as-prepared catalyst shows the bifunctional catalytic activity toward oxygen reduction reaction as well as oxygen evolution reaction in presence and absence of visible light. Under light conditions, δ-MnO2 shows 11.56% increment in bifunctional activity. Moreover, the doped MnO2 sample exhibits 19.23% increment in bifunctional activity as compared with pristine δ-MnO2. Upon light irradiation, the doped MnO2 cathode electrode can execute four times enhancement in power density, 2.38% improvement in voltage difference between charging and discharging and 16.26% increment in round-trip efficiency. This work provides a simple and easy method to prepare stable and durable photoactive bifunctional catalysts for energy storage applications.

Thermodynamic assessment of effect of ammonia, hydrazine and urea on water gas shift reaction

In the present study, thermodynamic calculations have been carried out on water gas shift reaction in presence of some selected chemical additives such as ammonia, hydrazine, and urea to understand their impact on the hydrogen generation and carbon suppression. The calculations were performed in a temperature range of 300–1300 K at constant pressure (1 bar) while varying the amount of additives from 0.5 to 2 mol. The results suggest that urea has the highest potential for hydrogen enrichment; however, it also increases carbon formation within the investigated conditions, as compared to other additives, ammonia and hydrazine, which suppress carbon formation along with assisting in hydrogen production. Hydrazine was found to be the most effective in reducing carbon and a molar ratio of N2H4:CH4:CO of 1.5:1:1 was sufficient for completely removing carbon throughout the temperature range of 300–1300 K, as compared to 2:1:1 M ratio for NH3:CH4:CO. Both, ammonia and hydrazine, being hydrogen storage materials release hydrogen along with suppressing carbon, which results in suitable conditions for sustained long term catalytic experiments where catalyst poisoning by coking can be eliminated.

To unsnarl the mechanism of disinfection of Escherichia coli via visible light assisted heterogeneous photo-Fenton reaction in presence of biochar supported maghemite nanoparticles

Waterborne diseases caused by bacterial contamination of water sources remain one of the perilous public health challenges in low and middle-income countries. In this regards, we report a photo-Fenton like reaction for disinfection of water contaminated with common waterborne bacterium, Escherichia coli under visible light using biochar supported maghemite nanoparticles (M/biochar). Waste leaves of Cymbopogon flexuosus impregnated with ferric chloride were subjected to pyrolysis, which leads to the formation of M/biochar. M/biochar was found to be more effective than only Maghemite nanoparticles for disinfection of targeted bacterium in a photo-Fenton like process. Fluorescence and scanning electron microscopy images indicated compromization of bacterial cell membrane. Experimental evidence infers that hydroxyl radicals could be the major component responsible for disinfecting E. coli in the present process. Results obtained from Resazurin assay indicate that reactive oxygen species produced during photo-Fenton like reaction may have impeded the oxido-reductase protein system of the bacteria and hence hampered its metabolic activity. Proposed process has been successfully investigated for disinfection of real water samples contaminated with E. coli and treated water did not induce a noticeable toxic effect on the growth of maize plants and hence could have the potential for real world applications.

Fabrication of zinc/silver binary nanoparticles, their enhanced microbial and adsorbing properties

Monometallic ZnO nanoparticles were prepared by hydrolysis of zinc acetate with ammonium hydroxide solution. Bimetallic zinc-silver nanoparticles (ZnO-AgNPs) were prepared using metal displacement galvanic cell reaction in presence of cetyltrimethylammonium bromide (CTAB). The optical and photo-physical properties of both NPs were determined. Surface plasmon resonance (SPR) intensity of ZnO-AgNPs depends on the ratio of metal salt precursors and other experimental conditions. The optical band gap (2.98 eV), agglomeration number (26819.92), and molar concentration (1.14 × 10−4 mol/liter) of ZnO-AgNPs were determined. Langmuir adsorption monolayer, Freundlich, intraparticles diffusion and multilayer adsorption isotherms used for the determination of maximum adsorption efficiency and adsorption isotherm parameters to the removal of safranin dye from an aqueous solution. The kinetics of safranin removal has also been discussed with pseudo-first order, pseudo-second order, intraparticle diffusion and multilayer kinetic models. The antibacterial and antifungal activities of ZnO, Ag and ZnO-AgNPs were determined against human pathogens using growth kinetic and disk diffusion methods. The concentrations of ZnO-AgNPs have significant effect on the bacterial growth kinetics. The death rate constants increase with increasing the NPs concentrations. It has been found that the ZnO-AgNPs hold higher microbial activities than that of monometallic counterpart, ZnO and AgNPs. Mechanism of bacterial growth and death was discussed.

Ruthenium-Benzimidazole complex: Structural, optical and solvent-free catalytic studies

Two different applications namely catalytic oxidation under solvent free conditions and optical power limiting studies were done on a mixed ligand ruthenium complex containing benzimidazole moiety and Triphenylphosphine. The complex was evaluated for its potential catalytic activity on the alcohol oxidation reaction in presence of hydrogen peroxide (30% aqueous solution) as oxidant to synthesize the corresponding carbonyls and the highlight of the process was that the reaction proceeded without the presence of any solvent. Excellent selectivity was achieved by the Ruthenium catalyst Ru(L)PPh3Cl2 for conversion of aromatic alcohols to aldehydes under milder conditions. One another application namely the non-linear optical activity was also studied. This activity of the complex was extracted at 532 nm wavelength, by the Z-scan method. The experimental result displays strong nonlinear absorption in the ruthenium complex and found to be 15.55 cm/W concluding that the complex displays superior optical limitation.

Catalytic oxidative decomposition of H2S over MoS2/γ-Al2O3

MoS2 phases supported on Al2O3 with different content in the range 5–20 wt% were prepared, characterized and tested as catalysts for the H2S oxidative decomposition for the simultaneous production of hydrogen and sulphur. The chemical-physical characterization results have evidenced a good dispersion of MoS2 on Al2O3 support.With respect to the Al2O3, MoS2 loading influenced particularly the value of H2 yield and minimized the SO2 production without substantial differences in H2S conversion (~50%). In particular, the highest H2 yield was observed for the catalyst having a nominal MoS2 loading of 10 wt%.A predictive mathematical model of the H2S oxidative decomposition reaction in presence of 10 wt% MoS2-based catalyst was developed through the identification of the main reactions occurring in the system. The predictive capability of the model was verified in the temperature range between 1073 and 1273 K by varying also the H2S inlet concentration.

Investigation on corrosion protection behavior and adsorption of carbohydrazide-pyrazole compounds on mild steel in 15% HCl solution: Electrochemical and computational approach

The behavior of synthesized (E)-5-amino-3-(4-methoxyphenyl)-N′-(1-(4-methoxyphenyl)ethylidene)-1H-pyrazole-4-carbohydrazide [AMPC] and (E)-5-amino-N′-(4-chlorobenzylidene)-3-(4-chlorophenyl)-1H-pyrazole-4-carbohydrazide [ACPC] towards the corrosion protection of mild steel (MS) in 15% HCl solution was studied by gravimetric and electrochemical methods. The inhibitor AMPC and ACPC at an optimum concentration of 300 ppm showed 98.26% and 96.21% inhibition efficiency, respectively at 303 K temperature. Thermodynamic results conquer that both inhibitors followed mixed adsorption and results from polarization suggests the retardation of the cathodic as well as anodic reactions in presence of inhibitors. The Langmuir adsorption isotherm suggests the monolayer adsorption of inhibitors on the MS facet. The formation of protective layers of inhibitors on MS surface was confirmed by the outcomes of FESEM and AFM topographical details. The composition of adsorbed layers on the MS surface was studied by XPS analysis. The energy related to molecular orbital of inhibitors, and adsorption behavior was computationally examined by Density Functional Theory (DFT), calculation of Fukui functions and Monte-Carlo simulation (MCS) studies.

In-situ synthesis of titania nanosheet – CdS nanoparticle composites by combined hydrothermal – selective adsorption and reaction for enhanced photocatalytic activity

Abstract Here we report an in-situ procedure for the synthesis of titania nanosheet (TNS) – CdS nanoparticle composite having excellent phototocatalytic activity. Two dimensional TNS were synthesized via hydrothermal treatment. The TNS is made composites with CdS by an adsorption and reaction in presence of triethanolamine. The characterizations were done by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and diffuse reflectance spectroscopy (DRS). Photocatalytic performance was studied using methylene blue degradation and confirmed by coumarin fluorescence probe method. Different TNS/CdS composites with increasing Cd/Ti molar ratio (TNS/0.1CdS, TNS/0.5CdS & TNS/1CdS) were prepared and better result is achieved with TNS/0.5CdS.

Catalyst‐Free and Metal‐Free Approach towards Synthesis of Amide‐ and Thioamide‐Linked β‐Carboline‐Pyridine Conjugates and Estimation of Their Photophysical Properties

AbstractA series of novel β‐carboline‐pyridine conjugates linked though amide and thioamide tethers were synthesized under catalyst‐free and metal‐free conditions using β‐carboline alkaloid; Kumujian C as a template. The tert‐butyl hydroperoxide (TBHP)‐mediated reaction with 2‐aminopyridines provided the amide linked β‐carboline‐pyridine conjugates whereas the Willgerodt‐Kindler reaction in presence of elemental sulfur furnished thioamide tethered analogues. The alkyl, aryl, as well as heteroarylamines underwent Willgerodt‐Kindler reaction with Kumujian C to afford diverse β‐carboline linked thioamides. Both the protocols avoided the use of toxic metal catalysts and expensive additives to provide the products in moderate to excellent yields in a short duration. Interestingly, the amide linked β‐carboline‐pyridine conjugates displayed excellent photophysical properties with fluorescence quantum yields (ΦF) up to 38% rendering them as promising candidates for applications in biology and optoelectronic materials.

Unsteady MHD Casson Dissipative Fluid Flow past a Semi-infinite Vertical Porous Plate with Radiation Absorption and Chemical Reaction in Presence of Heat Generation

Unsteady MHD Casson Dissipative Fluid Flow past a Semi-infinite Vertical Porous Plate with Radiation Absorption and Chemical Reaction in Presence of Heat Generation

Polypyrrole inter-layered low temperature curing benzoxazine matrices with enhanced thermal and dielectric properties

In the present work, curing reaction of benzoxazine was studied with the incorporation of different weight percentage of polypyrrole (PPy). Conventional benzoxazine derived from Bisphenol-F, aniline (BF-a) and bio-based benzoxazine derived from cardanol, furfurylamine (C-f) were synthesized and studied. Significant change in curing temperature (Tp) was observed with the addition of PPy to both C-f and BF-a monomers. With the incorporation of 5 wt% PPy, the Tp of C-f significantly reduced from 245 °C to 185 °C and similarly for BF-a monomer from 226 °C to 165 °C. The plausible mechanism of the benzoxazine ring opening reaction in presence of PPy is also discussed. Further, scanning electron microscopy (SEM) and X-ray diffraction studies suggest that the incorporation of PPy leads to the formation of fractal morphology. Consequently, the PPy inter-layered poly(C-f) and poly(BF-a) matrices contribute to the achievement of low value of dielectric constant (K = 3.39 and 3.83). In addition, PPy interlayer provokes enhanced thermal stability and higher LOI value. Thus, the present work demonstrates the catalytic role of PPy towards the curing reaction of benzoxazines and its contribution towards thermal and dielectric behaviour the of resulted matrices.