Influence Of Carboxylic Acids Research Articles

Influence of Carboxylic Acids on the Nucleation of Cementitious Phases Studied by Titrimetric Methods

AbstractIt is important to accurately control the setting of concrete and mortars. Functional admixtures such as hydroxy carboxylic acids can modify the hydration mechanism by influencing the dissolution of clinker phases and the crystallization of hydrate phases. While the crystallization of phases like CaCO3 under the influence of various additives has been studied intensively, there is substantially less understanding with regard to the main products of cement hydration, i.e., C‐S‐H, portlandite, ettringite, etc. In this work a potentiometry based setup was used to study the influence of succinic, tartaric, and citric acid on the nucleation and growth of portlandite and C‐S‐H. We found that the investigated molecules not only lead to a significant delay in nucleation by stabilization of prenucleation clusters, but also show a strong influence on the process of crystal growth. Further the effect of these molecules on the hydration reaction of tricalcium silicate was examined using ex‐situ calorimetry. We found a decent retarding effect on this reaction, even when there was almost no observable effect on the nucleation process in the previous experiments.

Influence of carboxylic acids on structural, optical, thermal, and electrical properties of ferroelectric glycine phosphite single crystals

Influence of carboxylic acids on structural, optical, thermal, and electrical properties of ferroelectric glycine phosphite single crystals

Influence of carboxylic acids on the performance of trivalent chromium electrolytes for the deposition of functional coatings

As a direct consequence of the restrictions on the use of hexavalent chromium compounds, the demand for a suitable replacement has arisen. In this work the electrodeposition of thick chromium layers (>1 µm) from a trivalent electrolyte is investigated with the aim to identify an electrolyte composition for the deposition of hard functional coatings. These layers can be used to surface finish tribological components experiencing high wear rates or mechanical stress in applications such as coating printing cylinders, feed rollers or piston rods. The influence of different carboxylic acids (malonic acid, malic acid, glycolic acid) on the deposition has been studied. The effect of current density on the current efficiency was investigated using in-situ microgravimetry. For a technical application the electrolyte containing malonic acid was the most promising one and was further investigated regarding the properties of the deposits, such as surface morphology, crack formation, composition, thickness and hardness, aiming at properties as close as possible to those of hexavalent chromium. In comparison to hexavalent chromium, the layer of trivalent chromium showed the same properties in terms of crack formation, hardness and layer thickness (> 1 µm).

Influence of carboxylic acid in the production of epoxidized soybean oil by conventional and ultrasound-assisted methods

This study investigated the production of epoxidized soybean oil by conventional and ultrasound-assisted methods. Epoxidized soybean oil was synthesized by reacting soybean oil, hydrogen peroxide, and carboxylic acid (formic or acetic acid). Sulfuric acid was used as a peroxidation catalyst. The effects of sonication, the carboxylic acid (formic and acetic acid), peroxidation catalyst (H2SO4), and temperature (50, 60, and 80 °C) were evaluated on the yield and productivity of epoxidized soybean oil. The reaction was carried out for 5 h in the conventional method and for 3 h in the ultrasound-assisted method. In both conventional and ultrasound-assisted methods, soybean oil yields into epoxidized soybean oil surpassed 90% only when formic acid and sulfuric acid were applied. The conventional method occurred faster than the sonochemical method for yields of up to 90%. The ultrasound-assisted method was the best technological option to attain a product of high purity (98%). The sonochemical method could be considered a promising technology if the ultrasound equipment’s limitations can be overcome.

Effect of Li2CoMn3O8 Nanostructures Synthesized by a Combustion Method on Montmorillonite K10 as a Potential Hydrogen Storage Material

This paper outlines new design nanocomposites (Li2CoMn3O8/K10) for electrochemical hydrogen storage with an emphasis on the optimal conditions to achieve higher performance. Li2CoMn3O8/K10 nanocomposites were fabricated by loading different ratios of the Li2CoMn3O8 (5%, 10%, and 20%) inside the montmorillonite K10. Electrochemical properties of the samples montmorillonite K10, Li2CoMn3O8, and the respective nanocomposites were studied by chronopotentiometry charge–discharge techniques in alkaline medium. The Li2CoMn3O8 nanostructures were synthesized by a facile combustion method in the presence of various carboxylic acids as fuel and capping agents. The influence of carboxylic acids on the size, morphology, and homogeneity of the samples was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Fourier transform infrared (FT-IR) were applied to investigate the purity and chemical compositions of the samples. ...

Influence of carboxylic acids on mechanical properties of thermoplastic starch by spray drying

Biodegradable packaging is gaining much attention in food industry as the awareness on sustainability has increased. Thermoplastic starch is a possible alternative. This study evaluated the influence of malic acid (MA) and citric acid (CA), used as a plasticizer, on the mechanical properties of thermoplastic starch (TPS) obtained by spray drying. TPS powder was produced from solution spray drying. This powder was further compression molded to prepare TPS dog-bone test samples. X-ray Diffraction (XRD) results showed that both the spray dried TPS powder and dog-bone test samples were amorphous in nature irrespective of the amount of plasticizer added. Scanning electron microscope (SEM) was used to examine the morphology of solution spray dried TPS powder. No noticeable difference was observed in the morphology. Particles were spherical in shape with homogenous surface. The FT-IR analysis indicated the interaction of plasticizers with starch chains by hydrogen bonding. During TGA analysis, apart from moisture loss at 100 °C, samples were thermally stable up to 170 °C. Mechanical testing of TPS dog-bone revealed that sample containing malic acid as plasticizer exhibited a more elastic behavior as compared to citric acid plasticized formulations. It was revealed that the tensile strength of TPS dog-bone samples was inversely proportional to the quantity of plasticizer used.

Low-molecular-weight components of the metabolome control the proliferative activity in cellular and bacterial cultures.

The effects of blood metabolites and model cell culture exometabolites found in the human and animal blood metabolomes have been assessed. Specifically, the influence of carboxylic acids that are structural analogues of amino acids and the drug Aktoflor-C have been studied. Methods of organotypic culturing of rat tissues and Escherichia coli bacterial culturing have been used. It has been found that all the tested compounds either stimulate or inhibit cell proliferation in tissue cultures and proliferation in bacterial cultures. The metabolites that are present in blood and interstitial fluids can exert regulation effects on the tissues of the body and intestinal microbiota.

Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins.

Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel’s ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators.

Influence of Carboxylic Acids on Poly(lactic acid)/Thermoplastic Starch Biodegradable Sheets Produced by Calendering–Extrusion

ABSTRACTSheets of poly(lactic acid) (PLA) and thermoplastic starch (TPS) with citric and adipic acid additives were produced through a calendering–extrusion process at pilot scale, and its mechanical, barrier, thermal, and morphological characteristics were determined. According to the micrographs, citric acid improved the fragmentation and dispersion of starch granules by facilitating interactions with PLA chains and increasing interfacial adhesion. Citric acid also induced a significant increase in the tensile strength and elongation at break, reducing water vapor permeability, increasing crystallinity, but decreased slightly the thermal stability. Adipic acid did not demonstrate the same efficiency, even when mixed with citric acid.

Inception of Acetic Acid/Water Cluster Growth in Molecular Beams.

The influence of carboxylic acids on water nucleation in the gas phase has been explored in the supersonic expansion of water vapour mixed with acetic acid (AcA) at various concentrations. The sodium-doping method has been used to detect clusters produced in supersonic expansions by using UV photoionisation. The mass spectra obtained at lower acid concentrations show well-detected Na(+) -AcA(H2O)n and Na(+)-AcA2 (H2O)n clusters up to 200 Da and, in the best cooling expansions, emerging Na(+)-AcAm (H2O)n signals at higher masses and unresolved signals that extend beyond m/e values >1000 Da. These signals, which increase with increasing acid content in water vapour, are an indication that the cluster growth taking place arises from mixed water-acid clusters. Theoretical calculations show that small acid-water clusters are stable and their formation is even thermodynamically favoured with respect to pure water clusters, especially at lower temperatures. These findings suggest that acetic acid may play a significant role as a pre-nucleation embryo in the formation of aerosols in wet environments.

Carboxylic Acids Promoted Speier’S Catalyst for the Hydrosilylation of Styrene with Triethoxysilane: Activity, Selectivity, and Mechanism

Catalytic performances of Speier's catalyst with carboxylic acids were studied in the hydrosilylation reaction of styrene with triethoxysilane. The effect of carboxylic acids (RCOOH) with different pKa values and size was investigated, and the temperature and n(COOH)/n(Pt) ratios were also studied. The catalytic activity of the hydrosilylation reaction is related to the acid strength of the carboxylic acid, temperature, and n(COOH)/n(Pt) ratio, while the selectivity for the β-adduct is related to the size of carboxylic acid and the n(COOH)/n(Pt) ratio. Moreover, the influence of carboxylic acid on the hydrosilylation reaction was explained with the help of density functional theory calculations, and a reasonable mechanism was proposed.

Special features of ethylene epoxidation by peroxyacetic acid

The B3LYP/6-31G(d, p) method of density functional theory was used to study the influence of carboxylic acid and water molecules on parallel ethylene oxidation reactions (epoxidation and hydroxylation) by peroxyacetic acid with the formation of various products. It was shown that carboxylic acid in the nondissociated form always present in the reaction mixture for several reasons had a catalytic action on this reaction and therefore contributed to an increase in its selectivity. We also found that the water molecule and its dimer facilitated epoxide formation. The suggestion was made that, if the reaction was performed in an aqueous medium, where the acid dissociated, the situation could radically change, and the hydroxylation reaction with the formation of glycol and/or its ester of the corresponding carboxylic acid would become predominant.

Photocatalytic degradation of organics in water in the presence of iron oxides: Influence of carboxylic acids

The effects of four carboxylic acids: malic, citric, tartaric and oxalic acids on the leaching of iron from two commercial iron oxides (hematite, α-Fe2O3, and magnetite, Fe3O4) have been investigated. The variables studied were the doses of iron oxides and carboxylic acids used as well as aqueous pH, temperature and the presence of hydrogen peroxide and/or UV-A radiation. On the whole, Fe3O4 led to higher amounts of leached iron than α-Fe2O3, and oxalic acid was the most effective carboxylic acid used. The importance of iron leaching has been considered to explain the photodegradation of bisphenol A (BPA) by UV-A/iron oxides systems. The influence of the presence of hydrogen peroxide and/or titania on the efficiency of these oxidation systems was also investigated. At the conditions tested, advanced oxidation with the UV-A/iron oxide/oxalic acid/H2O2/TiO2 system led to the lowest BPA half life (<15 min) among those processes studied.

Influence of Carboxylic Acids on the Synthesis of Chlorohydrin Esters from 1,3‐Butanediol

The influence of diverse carboxylic acid on the preparation of chlorohydrin esters using a one‐pot esterification–chlorination reaction, in which one of the reagents (chlorotrimethylsilane) acts as solvent, is described. Whereas the acid with low pKa provided higher amounts of the 2‐chloro regioisomer, the ones with higher pKa rendered the 1‐chloro regioisomer in 80% yield. These results are in accordance with the mechanism proposed in a previous article.

Influence of carboxylic acids on fixation of copper in wood impregnated with copper amine based preservatives

The importance of copper/amine based preservatives is increasing. Leaching of copper from wood preserved with these solutions is still higher than leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic acids (octanoic, 2-ethylhexanoic, decanoic) were added to copper/amine/boron aqueous solutions. An experiment of leaching of copper from Norway spruce was performed according to the modified standard procedure (EN 1250). Results confirmed that carboxylic acids significantly improve copper fixation. The best fixation was determined in specimens impregnated with the preservative solutions consisting of copper, ethanolamine, boric acid and octanoic acid. From such wood, only 1.6% of copper was leached.

Influence of Capping Groups on the Synthesis of γ-Fe2O3 Nanocrystals

Monodisperse and uniform γ-Fe2O3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe2O3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well.

Influence of Carboxylic Acid on the Photocatalytic Reduction of Cr(VI) Using Commercial TiO2

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTInfluence of Carboxylic Acid on the Photocatalytic Reduction of Cr(VI) Using Commercial TiO2G. Colón, M. C. Hidalgo, and J. A. NavíoView Author Information Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC−Universidad de Sevilla, Avda. Americo Vespucio s/n, 41092 Sevilla, Spain Cite this: Langmuir 2001, 17, 22, 7174–7177Publication Date (Web):October 4, 2001Publication History Received28 May 2001Revised23 July 2001Published online4 October 2001Published inissue 1 October 2001https://doi.org/10.1021/la010778dCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views692Altmetric-Citations70LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (53 KB) Get e-AlertsSUBJECTS:Oxides,Photocatalysis,Photocatalysts,Photodegradation,Redox reactions Get e-Alerts

Influence of carboxylic acids on the reactions with chlorotetraacetatodiruthenium(II,III): X-ray crystal structure of [Ru 2(μ-O 2CC 4H 3S) 4(OPPh 3) 2]BF 4·2H 2O

The reaction of Ru 2Cl(μ-O 2CCH 3) 4 with indole-2-carboxylic, N-methyl-pyrrole-2-carboxylic, furane-2-carboxylic, thiophene-2-carboxylic and benzofurane-2-carboxylic acids, which contain nitrogen, oxygen or sulphur atoms in the α position with respect to the carboxylate group, leads to compounds of the type Ru 2Cl(μ-O 2CR) 4. In these compounds O,O-coordination of the carboxylate ligands has been found. The analogous reaction with quinoline-2-carboxylic acid (Hquin) gives a disproportionation process with formation of Ru(quin) 3 and Ru 2(quin) 4; in this case, N,O-coordination of the ligand has been observed. The indole-2-carboxylato derivative has a non-polymeric structure, whereas with the other ligands polymeric structures with chlorine atoms bridging Ru 2 5+ units are formed. Treatment of Ru 2Cl(μ-O 2CR) 4 in thf or acetone with AgBF 4 gave [Ru 2(μ-O 2CR) 4L 2]BF 4 (L = thf, acetone; R = N-methyl-2-pyrrolyl, 2-furyl, 2-thienyl) or [Ru 2(μ-O 2CR) 4]BF 4 (R = 2-benzofuryl). The axial positions of these compounds can be occupied by OPPh 3 to give the corresponding [Ru 2(μ-O 2CR) 4(OPPh 3) 2]BF 4 The compounds have been characterized by analytical, spectroscopic and magnetic data. The structure of [Ru 2(μ-O 2CC 4H 3S) 4(OPPh 3) 2BF 4·2H 2O has been determined by X-ray crystallography. The dinuclear cation has two ruthenium atoms linked by four bridging thiophene-2-carboxylate ligands and two OPPh 3 ligands coordinated to axial positions, with an Ru—Ru distance of 2.2747(11) Å.

Mg^ 存在下でのカルサイト形成におけるカルボン酸の影響 : 溶液成長III

Mg^ 存在下でのカルサイト形成におけるカルボン酸の影響 : 溶液成長III

Influence of carboxylic acids on wheat carboxypeptidase - Their inhibition modes and effect of citric acid on stabilization in spray drying.

Spray drying was investigated as one of the drying methods expected to be useful for the production of powdered wheat carboxypeptidase. Heat stability test revealed that crude enzyme preparation was stable up to 50°C for 45min. Recrystallized enzyme was in hibited by oxalic acid, succinic acid, malic acid, citric acid, and maleic acid at conce ntrations of 10 mM and 50mM. Tartaric acid and fumaric acid did not inhibit the enzyme. The inhibition type and the Ki value for di- and tri-carboxylic acids, which acted as an inhibitor for the enzyme, were examined. Oxalic acid, malic acid, and maleic acid served as a noncompetitive inhibitor and their Ki values were 7.0, 12, and 24mM, respectively. Succinic acid was an inhibitor of mixed type and its Ki value, 10mM. Citric acid showed a competitive inhibition and the smallest Ki value, 4.4mM, among the inhibitors tested. The enzyme extracted with 0.04M citric acid solution was spray-dried in a yield of 100%.