Presence Of Carboxylic Acids Research Articles

Selectivity shift from paraffins to α-olefins in low temperature Fischer-Tropsch synthesis in the presence of carboxylic acids.

A shift of selectivity to long chain α-olefins has been observed during Fischer-Tropsch synthesis over Co catalysts in the presence of carboxylic acids. The total selectivity to α-olefins of 39% was obtained in the presence of acids. The effect has been ascribed to intermediate formation of esters which hinder secondary olefin hydrogenation.

Screening Precursor-Solvent Combinations for Li4Ti5O12 Energy Storage Material Using Flame Spray Pyrolysis.

The development and industrial application of advanced lithium based energy-storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor materials. Flame spray pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process control, material versatility, and cost. In the present study, phase pure anode material Li4Ti5O12 (LTO) was designed using FSP via extensive systematic screening of lithium and titanium precursors dissolved in five different organic solvents. The effect of precursor and solvent parameters such as chemical reactivity, boiling point, and combustion enthalpy on the particle formation either via gas-to-particle (evaporation/nucleation/growth) or via droplet-to-particle (precipitation/incomplete evaporation) is discussed. The presence of carboxylic acid in the precursor solution resulted in pure (>95 mass %) and homogeneous LTO nanoparticles of size 4-9 nm, attributed to two reasons: (1) stabilization of water sensitive metal alkoxides precursor and (2) formation of volatile carboxylates from lithium nitrate evidenced by attenuated total reflection Fourier transform infrared spectroscopy and single droplet combustion experiments. In contrast, the absence of carboxylic acids resulted in larger inhomogeneous crystalline titanium dioxide (TiO2) particles with significant reduction of LTO content as low as ∼34 mass %. In-depth particle characterization was performed using X-ray diffraction with Rietveld refinement, thermogravimetric analysis coupled with differential scanning calorimetry and mass spectrometry, gas adsorption, and vibrational spectroscopy. High-resolution transmission electron microscopy of the LTO product revealed excellent quality of the particles obtained at high temperature. In addition, high rate capability and efficient charge reversibility of LTO nanoparticles demonstrate the vast potential of inexpensive gas-phase synthesis for energy-storage materials.

Bacteria- and Fungicidal Action of Ag, Au, ZnO, SiO2 Nanoparticles in Presence of Carboxylic Acid in Polymer Matrix

Bacteria- and Fungicidal Action of Ag, Au, ZnO, SiO₂ Nanoparticles in Presence of Carboxylic Acid in Polymer Matrix

A kinetic study on the conversion of nylon 12 to methyl 12-hydroxydodecanoate in supercritical MeOH in the presence of carboxylic acid

Polyamides were effectively converted into hydroxyl esters by treatment with supercritical MeOH in the presence of glycolic acid. This transformation progressed smoothly over a period of 240 min, and the presence of glycolic acid accelerated the reaction. Kinetic analyses of the depolymerization of nylon 12 were performed by measuring the product distribution in the reaction mixture. The chemoselectivity of hydroxyl ester formation was linearly dependent on the amount of glycolic acid used. The product distribution of the reaction using pivalic acid was also measured. Simulations based on the actual time-course data enabled the estimation of kinetic parameters. The obtained kinetic parameters revealed that the rate constant for the formation of the hydroxyl ester was significantly enhanced by the presence of glycolic acid. These results clearly indicate that the monomeric unit, an amino ester, underwent a bimolecular substitution reaction with glycolic acid. Based on these results, we proposed a reaction mechanism for the formation of hydroxyl esters. Arrhenius plots of the reaction rates were used to effectively estimate the activation energy for each step.

Effects of organic acids on the leaching process of ion-adsorption type rare earth ore

To examine the activation of organic acids on the leaching process of ion-adsorption type rare earth ore (IRE-ore), the leaching behavior of rare earth (RE) and zeta potential of IRE-ore were investigated in the absence and presence of carboxylic acids. The results show that all the tested organic acids (acetic acid, malonic acid, citric acid, tartaric acid, succinic acid, and malic acid) can promote RE extraction. At relatively high concentrations of organic acids, the activation efficiency of organic acids on RE extraction is generally consistent with their complexation ability; whereas at their low concentrations, the change of zeta potential on the IRE-ore surface with organic acid concentration and pH has a close association with RE extraction, which indicates that organic acids can impact the surface electrical property of IRE-ore via their adsorption/desorption, and thereby increase/decrease the affinity of RE ions to IRE-ore. Therefore the influence of organic acids on the IRE-ore surface electrical property also plays an important role in RE extraction in addition to their complexation with RE ions.

Substitution of aluminous cement by calcium carbonates in presence of carboxylic acid

This paper presents results concerning the partial substitution of a calcium aluminate cement by calcium carbonate. The experimental parameters monitored in this study are the mechanical properties, the microstructure evolution through density measurements and the structure through analysis by X-ray diffraction.The major results of this study are the following: (1) It is possible to substitute a portion (10wt%) of an aluminous cement by calcium carbonate, while improving the mechanical properties of the hardened material. This is achieved with a mass percentage of the carboxylic acid between 1 and 5%, relative to the dry mass, which acts as a good dispersant and leads therefore to densification of the hardened material. (2) When the mix consists of 50wt% of aluminous cement and 50wt% of calcium carbonate, the mechanical properties of the cured material are low and this happens whatever the percentage of added dispersant is.

Functionalization of Multi-Wall Carbon Nanotubes in Chemical Solution of H<sub>2</sub>SO<sub>4</sub>/HNO<sub>3</sub> and its Dispersion in Different Media

The usage of multi-wall carbon nanotubes (MWCNTs) as reinforcement has been limited due to difficulties associated with dispersion of MWCNTs during the processing and poor adhesion between MWCNTs and matrix. In this paper, the effect of chemical functionalization with strong acid on the dispersion of MWCNTs were studied. The functionalization of MWCNTs were performed in chemical solution of sulphuric acid (H2SO4) and nitric acid (HNO3) with ratio of 3:1 and prepared at 80°C for 4 hours. The pristine MWCNTs (PMWCNTs) and acid treated MWCNTs (AMWCNTs) were analyzed using TEM, XRD, FTIR and Pycnometer density. The effect of dispersion of PMWCNTs and AMWCNTs was studied in three different matrices which are in aqueous media (distilled water), metal matrix and polymer matrix. The XRD results determined that the impurities in pristine MWCNTs such as NiZn3 have been removed after the purification process. The presence of carboxylic acid (-COOH) and hydroxyl (-OH) functional groups were determined using FT-IR. Based on the dispersion analysis in aqueous media, PMWCNTs were poor in suspension stability. While, the TEM images showed less agglomeration of the AMWCNTs compared to PMWCNTs and obtained a uniform dispersion in metal matrix (Cu) and polymer (epoxy) matrix composites.

Photoreactivity of monofluorinated 2-azidobenzimidazoles towards carboxylic acids

Abstract Aiming at the development of new photolabeling agents, the synthesis and photoreactivity of all monofluorinated derivatives of 2-azido-1-methylbenzimidazole are described. In the case of 4-, 5-, or 7-fluorination, irradiation in the presence of carboxylic acids (300 nm, Rayonet) afforded the monofluorinated 2-amino-6-acyloxybenzimidazoles in a regioselective manner, presumably after conversion of the initially formed nitrene to the N-cyanodiazaxylylene. Incorporation of chloride was also possible, and yields were comparable to those observed for the non-fluorinated parent compound. When blocking the reactive 6-position by a fluoro substituent, the title reaction was not possible. The analysis of the 19F NMR chemical shifts of the 5- and 7-monofluorinated products allowed the distinction between carboxylates and other nucleophiles.

ChemInform Abstract: Diastereoselective Synthesis of Structurally and Stereochemically Diversified 2‐Oxa‐7‐azabicyclo[4.1.0]hept‐3‐enyl Carboxylates and Their Potential Application Toward the Synthesis of Functionalized Pyranooxazolone and Pyrrole Derivatives Through Skeletal Transformations.

An advanced protocol for the diastereoselective intramolecular aziridination reaction has been developed to synthesize 2-oxa-7-azabicyclo[4.1.0]hept-3-en-1-yl carboxylates from their corresponding 4-H-pyrans and spiropyrans analogues employing iodosylbenznene as the exclusive oxidant in the presence of carboxylic acid and triethylamine. High structural and stereochemical diversity of these pyran fused NH-azridine scaffolds makes them useful in evaluating their biological and pharmacological activities by SAR studies. Additionally, their potential synthetic application has been uncovered by efficient transformation into biologically relevant novel pyranooxazolone and pyrrole derivatives.

Transforming Sugarcane Bagasse and Vinasse Wastes into Hydrochar in the Presence of Phosphoric Acid: An Evaluation of Nutrient Contents and Structural Properties

Sugarcane bagasse and vinasse are wastes generated at large scales by the Brazilian sugarcane industry. Therefore, new waste treatment and management practices are essential for a sustainable industrial growth and here we purpose the hydrothermal carbonization (HTC) to converts wet biomass into carbon-based solids. HTC of a mixture of sugarcane bagasse and vinasse was conducted at different temperatures, reaction times and phosphoric acid percentages. The chemical, structural and morphological properties of the hydrochars were evaluated by elemental analysis (CHNS), nutrient quantification (P, Ca, Mg, K), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the presence of phosphoric acid, the hydrochar yield increased as the ash content increased due to phosphate precipitates, as observed by XRD. The yield of the hydrochar decreased and the carbon and nitrogen content increased when the temperature increased from 180 to 230 °C. Hydrochars are amorphous and compositionally similar to lignites. The FTIR spectra showed bands at approximately 1700 and 1600 cm−1 in the hydrochar due to carboxylation and aromatization of the products, respectively. The presence of carboxylic acids is important due to their ability to interact with cations and hydrophilic molecules. Additionally, nutrients such as P, N, K, Ca, and Mg were concentrated in the hydrochar as inorganic phases. HTC applied to sugarcane bagasse and vinasse wastes produces hydrochars primarily containing carbon, nitrogen, and other nutrients as inorganic phases. Hydrochars could potentially be used as an agricultural fertilizer.

Iodobenzene Dichloride in the Esterification and Amidation of Carboxylic Acids: In‐Situ Synthesis of Ph3PCl2

A novel, in‐situ synthesis of dichlorotriphenylphosphorane (Ph3PCl2) is accomplished upon combining PPh3 and the easily prepared hypervalent iodine reagent iodobenzene dichloride (PhICl2). The phosphorane is selectively generated in the presence of carboxylic acid or alcohol residues to rapidly produce acyl chlorides and alkyl chlorides in high yields. Addition of EtOH, PhOH, BnOH, Et2NH or CH2N2 results in the direct synthesis of esters, amides and diazo ketones from carboxylic acids.

Diastereoselective Synthesis of Structurally and Stereochemically Diversified 2-Oxa-7-azabicyclo[4.1.0]hept-3-enyl Carboxylates and Their Potential Application toward the Synthesis of Functionalized Pyranooxazolone and Pyrrole Derivatives through Skeletal Transformations.

An advanced protocol for the diastereoselective intramolecular aziridination reaction has been developed to synthesize 2-oxa-7-azabicyclo[4.1.0]hept-3-en-1-yl carboxylates from their corresponding 4-H-pyrans and spiropyrans analogues employing iodosylbenznene as the exclusive oxidant in the presence of carboxylic acid and triethylamine. High structural and stereochemical diversity of these pyran fused NH-azridine scaffolds makes them useful in evaluating their biological and pharmacological activities by SAR studies. Additionally, their potential synthetic application has been uncovered by efficient transformation into biologically relevant novel pyranooxazolone and pyrrole derivatives.

Volatile organic compounds (VOCs) drive nutrient foraging in the clonal woodland strawberry, Fragaria vesca

It was previously demonstrated that stolons of Fragaria vesca respond to patches of varying nutrient quality; however, the mechanism of patch-detection remained unknown. Here we provide support for a process by which F. vesca perceives nutrient-rich patches, consistent with nutrient foraging prior to rooting. Volatile organic compounds (VOCs) emitted from unsterilized and sterilized field substrates were collected and analyzed by stir-bar headspace extraction gas chromatography-mass spectrometry using a method modified for soil and litter systems. Selected compounds were chosen to represent unsterilized and sterilized field substrates. These synthetic volatile compound mixtures were then applied to neutral substrate to test the ability of F. vesca to choose between unsterilized versus sterilized substrates. Primary stolons exhibited chemotropism towards unsterilized (natural) substrates and grew away from the sterilized volatile substrates when the alternate choice was a negative control. We conclude that the presence of carboxylic acids tends to stimulate stolon elongation and chemotropism while aldehydes, ketones and monoterpenes tend to suppress it. We provide evidence that developing stolons of F. vesca forage for nutrient-rich patches via volatile cues similar to those emitted from the soil through microflora activity.

In-Depth Insight into the Chemical Composition of Bio-oil from Hydroliquefaction of Lignocellulosic Biomass in Supercritical Ethanol with a Dispersed Ni-Based Catalyst

A comprehensive compositional analysis was conducted on biofuel obtained from woody biomass hydroliquefaction in supercritical ethanol with a dispersed Ni-based catalyst. Gas chromatography–mass spectrometry (GC–MS) and 1H nuclear magnetic resonance (NMR) were used to analyze the bio-oil compositions, and the results indicated the presence of carboxylic acid, ethyl ester, aldehyde, ketone, phenol, and its derivatives. As a result of the inherent limitations of these techniques, an intensive compositional characterization of bio-oil was accomplished through Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results revealed that the dominant oxygen-containing compounds were O2–O13 with double bond equivalent (DBE) values of 1–20 and carbon numbers of 10–25. The minor N1Ox class species with 4–15 carbon numbers and 10–35 DBE were also detected. The use of FT-ICR MS provided an in-depth compositional analysis of liquefaction-derived oil and would improve the understanding of biocrud...

Synthesis and Invitro Anti-Inflammatory activity of some 1, 2-disubstituted benzimidazoles

Fused heterocyclic compound, Benzimidazole formed by fusion of benzene and imidazole. Often the benzo derivative of imidazole is referred to as benzimidazole. Although it is the commonest name of the parent compound of the series, other names such as benzimidazole and 1, 3-benzodiazole are often used have wide range of diverse therapeutic applications. The synthesis of substituted benzimidazole derivatives thought remarkably effective compounds as anti-ulcers, anti-cancers, anti-malarials, anti-convulsants, anti-virals, antifungal and much more which have been reported in literature. A practical and convenient synthetic method which has been developed for the facile synthesis of 1, 2-disubstituted benzimidazoles is reported in the paper. The method described has the benefits of operational simplicity, excellent yields, and high chemo selectivity. In this present study, in the first step, 2-substituted benzimidazoles were synthesized which have been prepared by reaction of o-phenylenediamine with various carboxylic acids in presence of suitable solvent. Later, in the second step, the formed 2-substituted benzimidazoles reacts with chloroacetyl chloride in presence of base gives desired title compounds of 1, 2-disubstituted benzimidazole derivatives. All the structures of synthesized compounds have been purified by recrystalisation and thin layer chromatography which were further elucidated by elemental analysis, IR and 1H NMR spectral data. All the four synthesized compounds have been screened for their invitro anti-inflammatory activity using HRBC membrane stabilization method by comparing with standard drug Diclofenac sodium in the concentrations of 25 μg/mL, 50 μg/mL and 100 μg/mL. All the tested compounds exhibit significant invitro anti-inflammatory activity when compared with standard drug.

Microwave Synthesis of Some Novel 2-Substituted and N-Substituted Benzimidazole Derivatives and its Antimicrobial Activity

Benzimidazole and its derivatives represent one of the most biological active classes of literature. Two series of Benzimidazole derivatives were synthesized by the condensation reaction between o-phenylenediamine and carboxylic acids in presence of ring closing agents like HCl. The chemical structures of synthesized compounds were identified by the spectral analysis. The purity of compounds was determined by thin layer chromatography (TLC). The synthesized compounds have been screened for their antimicrobial activity by paper disc method.

A predictive multi-linear regression model for organic micropollutants, based on a laboratory-scale column study simulating the river bank filtration process

This study investigated relationships between OMP biodegradation rates and the functional groups present in the chemical structure of a mixture of 31 OMPs. OMP biodegradation rates were determined from lab-scale columns filled with soil from RBF site Engelse Werk of the drinking water company Vitens in The Netherlands. A statistically significant relationship was found between OMP biodegradation rates and the functional groups of the molecular structures of OMPs in the mixture. The OMP biodegradation rate increased in the presence of carboxylic acids, hydroxyl groups, and carbonyl groups, but decreased in the presence of ethers, halogens, aliphatic ethers, methyl groups and ring structures in the chemical structure of the OMPs. The predictive model obtained from the lab-scale soil column experiment gave an accurate qualitative prediction of biodegradability for approximately 70% of the OMPs monitored in the field (80% excluding the glymes). The model was found to be less reliable for the more persistent OMPs (OMPs with predicted biodegradation rates lower or around the standard error=0.77d−1) and OMPs containing amide or amine groups. These OMPs should be carefully monitored in the field to determine their removal during RBF.

Bioinspired Nonheme Iron Catalysts for C-H and C═C Bond Oxidation: Insights into the Nature of the Metal-Based Oxidants.

Recent efforts to design synthetic iron catalysts for the selective and efficient oxidation of C-H and C═C bonds have been inspired by a versatile family of nonheme iron oxygenases. These bioinspired nonheme (N4)Fe(II) catalysts use H2O2 to oxidize substrates with high regio- and stereoselectivity, unlike in Fenton chemistry where highly reactive but unselective hydroxyl radicals are produced. In this Account, we highlight our efforts to shed light on the nature of metastable peroxo intermediates, which we have trapped at -40 °C, in the reactions of the iron catalyst with H2O2 under various conditions and the high-valent species derived therefrom. Under the reaction conditions that originally led to the discovery of this family of catalysts, we have characterized spectroscopically an Fe(III)-OOH intermediate (EPR g(max) = 2.19) that leads to the hydroxylation of substrate C-H bonds or the epoxidation and cis-dihydroxylation of C═C bonds. Surprisingly, these organic products show incorporation of (18)O from H2(18)O, thereby excluding the possibility of a direct attack of the Fe(III)-OOH intermediate on the substrate. Instead, a water-assisted mechanism is implicated in which water binding to the iron(III) center at a site adjacent to the hydroperoxo ligand promotes heterolytic cleavage of the O-O bond to generate an Fe(V)(O)(OH) oxidant. This mechanism is supported by recent kinetic studies showing that the Fe(III)-OOH intermediate undergoes exponential decay at a rate enhanced by the addition of water and retarded by replacement of H2O with D2O, as well as mass spectral evidence for the Fe(V)(O)(OH) species obtained by the Costas group. The nature of the peroxo intermediate changes significantly when the reactions are carried out in the presence of carboxylic acids. Under these conditions, spectroscopic studies support the formation of a (κ(2)-acylperoxo)iron(III) species (EPR g(max) = 2.58) that decays at -40 °C in the absence of substrate to form an oxoiron(IV) byproduct, along with a carboxyl radical that readily loses CO2. The alkyl radical thus formed either reacts with O2 to form benzaldehyde (as in the case of PhCH2COOH) or rebounds with the incipient Fe(IV)(O) moiety to form phenol (as in the case of C6F5COOH). Substrate addition leads to its 2-e(-) oxidation and inhibits these side reactions. The emerging mechanistic picture, supported by DFT calculations of Wang and Shaik, describes a rather flat reaction landscape in which the (κ(2)-acylperoxo)iron(III) intermediate undergoes O-O bond homolysis reversibly to form an Fe(IV)(O)((•)OC(O)R) species that decays to Fe(IV)(O) and RCO2(•) or isomerizes to its Fe(V)(O)(O2CR) electromer, which effects substrate oxidation. Another short-lived S = 1/2 species just discovered by Talsi that has much less g-anisotropy (EPR g(max) = 2.07) may represent either of these postulated high-valent intermediates.

ChemInform Abstract: Palladium on Carbon‐Catalyzed Aqueous Transformation of Primary Alcohols to Carboxylic Acids Based on Dehydrogenation under Mildly Reduced Pressure.

AbstractThe clean and first dehydrogenation of primary alcohols to carboxylic acids in presence of a heterogeneous catalyst is presented.

Micellization of N-dodecylglucosylamine and its interaction with DNA in the presence of carboxylic acid

Sugar surfactants are a relatively new class of surfactants with carbohydrate as their hydrophilic part. So far, the studies about their physical chemical properties have been unsystematic. This paper reported the aggregation of surfactant N-dodecylglucosylamine and its binding with DNA in the presence of different carboxylic acids. We found that among propionic acid, butyric acid, and hexanoic acid, hexanoic acid made the surfactant exhibit the highest capability and efficiency for decreasing the surface tension of water and aggregate into micelles most efficiently. Once propionic acid (or butyric acid) was replaced with propanedioic acid (or succinic acid), the critical micelle concentration (cmc) for N-dodecylglucosylamine was decreased, while when hexanoic acid was replaced with adipic acid, cmc was increased. In the presence of DNA, the surfactant could aggregate at a concentration much lower than that without DNA. Moreover, DNA conformation was changed in N-dodecylglucosylamine/carboxylic acid systems and the change was observed more obviously in the presence of propionic acid and propanedioic acid.