Showing papers on "Carboxylic acid published in 2008"

Carboxylic acids as substrates in homogeneous catalysis.

Abstract: In organic molecules carboxylic acid groups are among the most common functionalities Activated derivatives of carboxylic acids have long served as versatile connection points in derivatizations and in the construction of carbon frameworks In more recent years numerous catalytic transformations have been discovered which have made it possible for carboxylic acids to be used as building blocks without the need for additional activation steps A large number of different product classes have become accessible from this single functionality along multifaceted reaction pathways The frontispiece illustrates an important reason for this: In the catalytic cycles carbon monoxide gas can be released from acyl metal complexes, and gaseous carbon dioxide from carboxylate complexes, with different organometallic species being formed in each case Thus, carboxylic acids can be used as synthetic equivalents of acyl, aryl, or alkyl halides, as well as organometallic reagents This review provides an overview of interesting catalytic transformations of carboxylic acids and a number of derivatives accessible from them in situ It serves to provide an invitation to complement, refine, and use these new methods in organic synthesis

Versatile Synthesis Strategy for Carboxylic Acid−functionalized Upconverting Nanophosphors as Biological Labels

Abstract: Up-converting rare-earth nanophosphors (UCNPs) have great potential to revolutionize biological luminescent labels, but their use has been limited by difficulties in obtaining UCNPs that are biocompatible. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into water-soluble and carboxylic acid-functionalized analogues by directly oxidizing oleic acid ligands with the Lemieux-von Rudloff reagent. This oxidation process has no obvious adverse effects on the morphologies, phases, compositions and luminescent capabilities of UCNPs. Furthermore, as revealed by Fourier transform infrared (FTIR) and NMR results, oleic acid ligands on the surface of UCNPs can be oxidized into azelaic acids (HOOC(CH2)7COOH), which results in the generation of free carboxylic acid groups on the surface. The presence of free carboxylic acid groups not only confers high solubility in water, but also allows further conjugation with biomolecules such as streptavidin. A highly sensitive DNA sensor based on such streptavidin-coupled UCNPs have been prepared, and the demonstrated results suggest that these biocompatible UCNPs have great superiority as luminescent labeling materials for biological applications.

Robust, Efficient, and Orthogonal Synthesis of Dendrimers via Thiol-ene “Click” Chemistry

Abstract: Dendrimers up to the fourth generation were successfully prepared via the divergent growth strategy using a combination of thiol-ene “click” chemistry and traditional esterification reactions. The thiol-ene reactions were conducted under solvent-free, ambient conditions at room temperature by irradiating with UV light. The fourth-generation dendrimers were subsequently functionalized with carboxylic acid, pyrene, and Fmoc-protected cysteine moieties via thiol-ene reactions.

Hierarchy of Supramolecular Synthons: Persistent Carboxylic Acid···Pyridine Hydrogen Bonds in Cocrystals That also Contain a Hydroxyl Moiety

Abstract: A Cambridge Structural Database (CSD) analysis was conducted in order to evaluate the hierarchy of supramolecular heterosynthons that involve two of the most relevant functional groups in the context of active pharmaceutical ingredients, carboxylic acids and alcohols, in competitive environments. The study revealed that 34% of the 5690 molecular carboxylic acid entries and 26% of the 25 035 molecular alcohol entries form supramolecular homosynthons, whereas the remaining entries form supramolecular heterosynthons with other functional groups, in particular Narom, CONH2, C−O−C, C═O, and chloride anions. Further refinement of this raw data revealed the following: 98% occurrence of the COOH···Narom supramolecular heterosynthon in the 126 crystal structures that contain acid and pyridine moieties in the absence of other hydrogen bond donors or acceptors; and 78% occurrence of the OH···Narom supramolecular heterosynthon in 228 crystal structures that contain hydroxyl and pyridine moieties (excluding intramolec...

Phenol degradation by advanced electrochemical oxidation process electro-Fenton using a carbon felt cathode

Abstract: Oxidation of phenol in aqueous media by electro-Fenton process using carbon felt cathode has been studied. The salts of iron, cobalt, manganese, and copper were used to provide the metal cations as catalyst of Fenton reaction to produce hydroxyl radicals. 10−4 M of soluble iron(II) sulfate salt supplied the optimum catalytic condition, allowing to remove 100% of total organic carbon (TOC) of aqueous phenol solutions. The main reaction intermediates formed during electro-Fenton treatment were identified as hydroquinone, p-benzoquinone, and catechol. Carboxylic acids such as maleic, fumaric, succinic, glyoxylic, oxalic, and formic were predominantly identified as end products, before complete mineralization. The absolute rate constant of phenol degradation by hydroxyl radicals was obtained in acid medium (2.5 < pH < 3.0), being equal to (2.62 ± 0.23) × 109 M−1 s−1. Experiments with electro-Fenton oxidation of each aromatic intermediate allowed to propose a complete mineralization pathway.

Base‐Induced Formation of Two Magnesium Metal‐Organic Framework Compounds with a Bifunctional Tetratopic Ligand

Abstract: Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60 % of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2 g–1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Activated carbon catalytic ozonation of oxamic and oxalic acids

Abstract: The oxidation of hazardous organic compounds leads to the formation of several by-products, being oxalic acid and oxamic acid final oxidation products refractory to ozonation. The present work aimed to study the ozonation of those carboxylic acids in the presence of activated carbon at different solution pH. For comparative purposes, experiments of adsorption on activated carbon, ozonation, and ozonation in the presence of activated carbon were carried out. In order to clarify the reaction mechanism, some experiments were done in the presence of a radical scavenger. With the aim of evaluating the role of the activated carbon surface chemistry during the ozonation, two activated carbon samples were assessed. A significant synergistic effect between ozone and activated carbon was evidenced in the oxidation of oxalic acid. Oxamic acid was found to be refractory to oxidation at pH 7. On the other hand, at pH 3, the mineralization of oxamic acid was significantly enhanced by the presence of activated carbon. Generally, the presence of activated carbon during ozonation increased the rate of degradation of both carboxylic acids leading to mineralization. Best results were achieved with the most basic activated carbon. In both cases, the efficiency of activated carbon promoted ozonation decreases with the increase of solution pH.

Decarboxylative Biaryl Synthesis from Aromatic Carboxylates and Aryl Triflates

Abstract: A new catalyst system, generated in situ from Cu2O, 1,10-phenanthroline, PdI2, and Tol-BINAP, for the first time allows the decarboxylative coupling of carboxylic acids with aryl triflates. In contrast to previous decarboxylative couplings that remained limited to certain activated carboxylates, e.g., ortho-substituted benzoates, this halide-free protocol is generally applicable to aromatic carboxylic acid salts regardless of their substitution pattern.

Formic acid electrooxidation on Pd in acidic solutions studied by surface-enhanced infrared absorption spectroscopy

Abstract: A mechanistic study of electrocatalytic oxidation of formic acid on Pd in sulfuric and perchloric acids is reported. Surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS) shows the adsorption of CO, bridge-bonded formate, bicarbonate, and supporting anions on the electrode surface. Poisoning of the Pd surface by CO, formed by dehydration of formic acid, is very slow and scarcely affects formic acid oxidation. The anions are adsorbed more strongly in the order of (bi)sulfate > bicarbonate > perchlorate, among which the most strongly adsorbed (bi)sulfate considerably suppresses formic acid oxidation in the double layer region. The oxidation is suppressed also at higher potentials in both acids by the oxidation of the Pd surface. Adsorbed formate is detected only when formic acid oxidation is suppressed. The results show that formate is a short-lived reactive intermediate in formic acid oxidation and is hence detected when its decomposition yielding CO2 is suppressed. The high electrocatalytic activity of Pd can be ascribed to the high tolerance to CO contamination and also high catalytic activity toward formate decomposition.

Catalytic Asymmetric Hiyama Cross-Couplings of Racemic α-Bromo Esters

Abstract: The first catalytic asymmetric cross-coupling of α-halo carbonyl compounds with aryl metal reagents has been developed, thereby generating synthetically useful α-aryl carboxylic acid derivatives in good enantiomeric excess. The method can also be applied to enantioselective alkenylation reactions.

Asymmetric organic synthesis with enzymes

Abstract: METHODOLOGY Medium Engineering: Directed evolution: The search for new enzymes: SYNTHETIC APPLICATIONS Dynamic Kinetic Resolutions: Deracemization and Enantioconvergent Processes: Transesterification and hydrolysis of carboxylic acid derivatives, alcohols and epoxides Aminolysis and ammonolysis of carboxylic acid derivatives: Reduction Reactions: Oxidation Reactions: Making and breaking C-C bonds:

Thermodynamical Equilibrium of Binary Supramolecular Networks at the Liquid-Solid Interface

Abstract: Coadsorption of two different carboxylic acids, benzenetribenzoic acid and trimesic acid, was studied at the liquid-solid interface in two different solvents (heptanoic and nonanoic acid). Independent alteration of both concentrations in binary solutions resulted in six nondensely packed monolayer phases with different structures and stoichiometries, as revealed by means of scanning tunneling microscopy (STM). All of these structures are stabilized by intermolecular hydrogen bonding between the carboxylic acid functional groups. Moreover, phase transitions of the monolayer structures, accompanied by an alteration of the size and shape of cavity voids in the 2D molecular assembly, could be achieved by in situ dilution. The emergence of the various phases could be described by a simple thermodynamic model.

Epoxidation of Canola Oil with Hydrogen Peroxide Catalyzed by Acidic Ion Exchange Resin

Abstract: Canola oil with an iodine value of 112/100 g, and containing 60% oleic acid and 20% linoleic acid, was epoxidised using a peroxyacid generated in situ from hydrogen peroxide and a carboxylic acid (acetic or formic acid) in the presence of an acidic ion exchange resin (AIER), Amberlite IR 120H. Acetic acid was found to be a better oxygen carrier than formic acid, as it produced about 10% more conversion of ethylenic unsaturation to oxirane than that produced by formic acid under otherwise identical conditions. A detailed process developmental study was then performed with the acetic acid/AIER combination. The parameters optimised were temperature (65 °C), acetic acid to ethylenic unsaturation molar ratio (0.5), hydrogen peroxide to ethylenic unsaturation molar ratio (1.5), and AIER loading (22%). An iodine conversion of 88.4% and a relative conversion to oxirane of 90% were obtained at the optimum reaction conditions. The heterogeneous catalyst, AIER, was found to be reusable and exhibited a negligible loss in activity.

Production Of Peracids Using An Enzyme Having Perhydrolysis Activity

Abstract: A process is provided for producing peroxycarboxylic acids from carboxylic acid esters. More specifically, carboxylic acid esters are reacted with an inorganic peroxide, such as hydrogen peroxide, in the presence of an enzyme catalyst having perhydrolysis activity. The present perhydrolase catalysts are classified as members of the carbohydrate esterase family 7 (CE-7) based on the conserved structural features. Further, disinfectant formulations comprising the peracids produced by the processes described herein are provided.

Synthesis of cyclic carbonates from carbon dioxide and epoxides over betaine-based catalysts

Abstract: A series of betaine-based salts containing quaternary ammonium ion and carboxylic acid group were synthesized by direct protonation of anhydrous betaine using different Bronsted acids. The catalytic activity of these salts for the synthesis of cyclic carbonates via cycloaddition reaction of CO2 with epoxides was studied. The effects of anions of the salts, reaction temperature, pressure, reaction time, and the amount of catalyst used on the reaction were studied. It was demonstrated that the carboxylic acid group in the catalyst had synergetic effect with halide anion, and high yield of cyclic carbonates and excellent selectivity could be achieved at optimized condition.

Effects of alkaline earth metal ion complexation on amino acid zwitterion stability: results from infrared action spectroscopy.

Abstract: The structures of isolated alkaline earth metal cationized amino acids are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and theory. These results indicate that arginine, glutamine, proline, serine, and valine all adopt zwitterionic structures when complexed with divalent barium. The IRMPD spectra for these ions exhibit bands assigned to carboxylate stretching modes, spectral signatures for zwitterionic amino acids, and lack bands attributable to the carbonyl stretch of a carboxylic acid functional group. Structural and spectral assignments are strengthened through comparisons with absorbance spectra calculated for low-energy structures and the IRMPD spectra of analogous ions containing monovalent alkali metals. Many bands are significantly red-shifted from the corresponding bands for amino acids complexed with monovalent metal ions, owing to increased charge transfer to divalent metal ions. The IRMPD spectra of arginine complexed with divalent strontium and barium are very similar and indicate that arginine adopts a zwitterionic form in both ions. Calculations indicate that nonzwitterionic forms of arginine are lowest in free energy in complexes with smaller alkaline earth metal cations and that zwitterionic forms are preferentially stabilized with increasing metal ion size. B3LYP and MP2 calculations indicate that zwitterionic forms of arginine are lowest in free energy for M = Ca, Sr, and Ba.

Carboxylic acid-containing benzoxazines as efficient catalysts in the thermal polymerization of benzoxazines

Abstract: The autocatalytic thermal polymerization behavior of three benzoxazine monomers containing carboxylic acid functionalities is reported. Several mixtures of these carboxylic monomers and 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine were prepared and their thermal polymerization behavior was analyzed by differential scanning calorimetry. The acid character of these reactive monomers increases the concentration of oxonium species, thus catalyzing the benzoxazine ring opening reaction. In this way the polymerization temperature decreased by as much as 100 °C in some cases. The existence of decarboxylation processes at high temperatures has been established by FTIR-ATR and related to the increase in thermal stability observed by TGA in some cases. A relationship between the presence of carboxylic groups in the resulting materials and their flame retardancy behavior has also been established. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6091–6101, 2008

Oxidation pathways of malachite green by Fe3+-catalyzed electro-Fenton process

Abstract: A very detailed scheme for the Fe3+-catalyzed electro-Fenton mineralization of malachite green as a model triarylmethane dye is presented. Bulk electrolyses of 250-mL aqueous solutions of 0.5 mM malachite green with 0.2 mM Fe3+ as catalyst have been carried out at room temperature and pH 3.0 under constant current in an undivided cell equipped with a graphite-felt cathode and a Pt anode to assess the performance of the electro-Fenton system. In situ electrogeneration of Fe2+ and H2O2 from quick cathodic reduction of Fe3+ and dissolved O2 (from bubbled compressed air), respectively, allows the formation of the very oxidizing species hydroxyl radical ( OH) in the medium from Fenton's reaction. A pseudo-first-order decay kinetics with an apparent rate constant of k1,MG = 0.244 min−1 was obtained for total destruction of malachite green by action of OH at 200 mA, requiring 22 min for total decoloration of the solution. In the same experimental conditions, overall mineralization was reached at 540 min. Up to 15 aromatic and short-chain carboxylic acid intermediates were identified along the treatment. The evolution of current efficiency was calculated from the chemical oxygen demand (COD) removal. Based on the time course of most of the by-products and the identification of inorganic ions released, some plausible mineralization pathways are proposed and thoroughly discussed. It has been found that the electro-Fenton degradation of malachite green proceeds via parallel pathways, all of them involving primary splitting of the triaryl structure initiated by attack of OH on the central carbon, thus yielding two different N-dimethylated benzophenones. Successive cleavage of the aromatic intermediates generates oxalic acid as the ultimate short-chain carboxylic acid, whereas N-demethylation of some of them produces formic acid as well. Oxalic acid and its Fe2+ complexes, as well as formic acid, can be slowly but totally mineralized by OH.

Radiation-sensitive composition for colored layer formation, color filter and color liquid crystal display element

Abstract: PROBLEM TO BE SOLVED: To provide a new radiation-sensitive composition for colored layer formation having good storage stability as an alkali-soluble resin itself, excellent in storage stability as a pigment dispersion and a liquid composition even if a high pigment concentration, and providing a colored layer which does not undergo a decrease in film retention, does not cause chipping of a pattern edge nor undercut even under low exposure energy and excels also in solvent resistance and adhesion to a substrate. SOLUTION: The radiation-sensitive composition for colored layer formation comprises (A) a colorant, (B) an alkali-soluble resin, (C) a polyfunctional monomer and (D) a photopolymerization initiator, wherein the alkali-soluble resin (B) comprises a copolymer having as essential constituents (b1) at least one selected from the group consisting of an unsaturated carboxylic acid or an acid anhydride thereof and an unsaturated phenol compound, (b2) an unsaturated compound having an alicyclic carbon ring structure and (b3) an unsaturated compound having an oxetane ring structure. COPYRIGHT: (C)2008,JPO&INPIT

Synergistic herbicidal composition containing certain pyridine or pyrimidine carboxylic acids and certain cereal and rice herbicides

Abstract: An herbicidal composition containing (a) a pyridine or pyrimidine carboxylic acid component and (b) a second cereal or rice herbicide component provides synergistic control of selected weeds.

Oxidation of Hydrocarbons

Abstract: In a process for oxidizing a hydrocarbon to the corresponding hydroperoxide, alcohol, ketone, carboxylic acid or dicarboxylic acid, a reaction medium comprising a hydrocarbon is contacted with an oxygen-containing gas in a reaction zone and in the presence of a catalyst comprising a cyclic imide. During the oxidation process, a portion of the reaction medium is continuously or intermittently removed from the reaction zone, is stripped of water and organic acid impurities and then returned to the reaction zone.

Asymmetric direct amide synthesis by kinetic amine resolution: a chiral bifunctional aminoboronic acid catalyzed reaction between a racemic amine and an achiral carboxylic acid.

Abstract: The formation of amide bonds by direct reaction of amines with carboxylic acids by thermal or catalytic methods is generally a high temperature process. There have been no reports to date of any reactions that involve asymmetric induction during direct amide formation, with the exception of an enzyme-catalyzed process. Lower temperatures are often preferred for any reaction as it can reduce the amount of reagent, reactant, or thermal product degradation. A more important consideration is that asymmetric induction processes are usually more efficient at lower temperatures because small differences in energy between diasteroisomeric transition states are amplified; however, there are an increasing number of examples where this is not the case and improved asymmetric induction can be obtained at higher temperatures. With these considerations in mind, we endeavored to develop a catalytic direct amide formation under mild conditions, though still well above room temperature. The current limiting temperature appears to be 85 8C, the temperature at which reactions can be carried out with bifunctional aminoboronic acid catalysts by using azeotropic water removal in fluorobenzene. Although these reaction conditions are relatively mild compared to all other direct amide formation reactions with boron-derived catalyts, they do not completely preclude the thermal direct amide formation with the more reactive carboxylic acid/amine combinations. Though the prospect of developing asymmetric catalysts for amide formation may not look promising, we report herein preliminary results that demonstrate asymmetric processes are possible under elevated temperatures with the development of a planar chiral ferrocenederived bifunctional aminoboronic acid catalyst. Our recent interests in the development of bifunctional aminoboronic acids as potential catalysts led to the development of N,N-di-iso-propylbenzylaminoboronic acid type catalysts such as commercially available 1 and planar chiral