Showing papers on "Carboxylic acid published in 2006"
TL;DR: In this paper, a functionalized amorphous carbon material with acid catalytic activity as a solid acid replacement for sulfuric acid was used for liquid-phase acid-catalyzed reactions.
Abstract: Carbonization of d-glucose at 573−723 K followed by sulfonation produces a functionalized amorphous carbon material with acid catalytic activity as a solid-acid replacement for sulfuric acid. The carbon material contains phenolic hydroxyl, carboxylic acid, and sulfonic acid groups and exhibits high catalytic performance for liquid-phase acid-catalyzed reactions. Carbonization at higher temperature followed by sulfonation also results in amorphous carbon, but the resultant does not exhibit catalytic activity although the amorphous carbon has sufficient amount of sulfonic acid groups. Structural and active site analyses suggest that the marked difference in catalytic activity is due to the accessibility of reactants to sulfonic acid groups in the carbon structure.
507 citations
TL;DR: A selective transformation of carboxylic acid moiety was found to occur exclusively at the position previously occupied by the acid, even in the presence of a reactive C-H group, allowing for the preparation of a variety of aryl-substituted heteroaromatics that would be difficult to obtain via other methods.
Abstract: Aryl-substituted five-membered heteroaromatics have attracted great interest over the past years due to their presence in a large number of pharmaceuticals and natural products. Recently, an advance in the preparation of these scaffolds was achieved by employing a C−H functionalization strategy. This method allows easy access to these biaryl motifs by precluding the necessity of preparing specific coupling partners, although poor regioselectivity is sometimes observed when more than one reactive C−H is present on the substrate. In an effort to circumvent this liability, we envisioned the use of a carboxylic acid moiety as a blocking group that could be later functionalized or removed. Remarkably, the coupling was found to occur exclusively at the position previously occupied by the acid, even in the presence of a reactive C−H group. This selective transformation was also found to proceed with other heteroaromatic carboxylic acids, allowing for the preparation of a variety of aryl-substituted heteroaromati...
335 citations
TL;DR: The self-consistent spectrophotometric acidity scale of neutral Brønsted acids in acetonitrile (AN) spanning 24 orders of magnitude of acidities is reported, and the structure-acidity relations are discussed.
Abstract: For the first time, the self-consistent spectrophotometric acidity scale of neutral Bronsted acids in acetonitrile (AN) spanning 24 orders of magnitude of acidities is reported. The scale ranges from pKa 3.7 to 28.1 in AN. The scale includes 93 acids that are interconnected by 203 relative acidity measurements (ΔpKa measurements) and contains compounds with gradually changing acidities, including representatives from all of the conventional families of OH (alcohols, phenols, carboxylic acids, sulfonic acids), NH (anilines, diphenylamines, disulfonimides), and CH acids (fluorenes, diphenylacetonitriles, phenylmalononitriles). The CH acids were particularly useful in constructing the scale because they do not undergo homo- or heteroconjugation processes and their acidities are rather insensitive to traces of water in the medium. The scale has been fully cross-validated: the relative acidity of any two acids on the scale can be found by combining at least two independent sets of ΔpKa measurements. The consi...
301 citations
TL;DR: In this paper, the kinetics of acetic acid esterification with methanol were investigated using a commercial Nafion/silica nanocomposite catalyst (SAC-13) and H 2 SO 4, respectively.
270 citations
TL;DR: In this article, chemical functionalised single-walled carbon nanotubes were formed using sonication in a mixture of concentrated sulphuric and nitric acids for varying lengths of time which resulted in carboxylic acid group functionalisation, predominantly at the ends.
264 citations
TL;DR: IR spectroscopy of transition metal-amino acid complexes in combination with DFT calculations is a very powerful structural tool, readily applicable to biomimetic systems that model, for example, the reaction centers of proteins in the solvent-free environment.
Abstract: Infrared multiple-photon dissociation (IR-MPD) spectroscopy has been applied to singly-charged complexes involving the transition metals Ag+ and Zn2+ with the aromatic amino acid phenylalanine. These studies are complemented by DFT calculations. For [Phe+Ag]+ the calculations favor a tridentate charge solvation N/O/ring structure. The experimental spectrum strongly supports this as the predominant binding geometry and, in particular, rules out a significant presence of the salt-bridge conformation. Zn2+ forms a deprotonated dimer complex with Phe, [Zn+Phe2−H]+, in which the +2 oxidation state serves as a useful biomimetic model for zinc protein sites. A number of low-energy conformations were located, of which the lowest-energy conformer predicted by the calculations involves a Phe ligand deprotonated on the carboxylic acid, while the other Phe ligand is in the tridentate charge solvation conformation. The calculated IR spectrum of this conformer gives a close fit to the experimental spectrum, strongly su...
222 citations
TL;DR: The results from DFT calculations and ab initio molecular-dynamics simulations of formic acid adsorption onto TiO2 are compared and match well with the experimental IR measurements, supporting the bridge-binding geometry of carboxylic-acid adsorb strongly to the surfaces in a bridge-coordinating mode.
220 citations
TL;DR: In this article, the impact of carboxylic acid chain length on the kinetics of liquid-phase acid-catalyzed esterification was investigated, and the reaction rate decreased as the number of carbons in the linear alkyl chain increased for both H 2 SO 4 and SAC-13.
213 citations
TL;DR: Co- and terpolyesters based on succinic acid and isosorbide in combination with other renewable monomers such as 2,3-butanediol, 1, 3-propanediol, and citric acid proved to be suitable materials for coating applications with respect to solvent resistance, impact resistance, and hardness.
193 citations
Patent•
27 Jun 2006TL;DR: In this paper, the authors provided electrically conducting polymer compositions comprising an electrically conductive polymer or copolymer and an organic solvent wettable fluorinated acid polymer, which can be used in organic electronic devices.
Abstract: There are provided electrically conducting polymer compositions comprising an electrically conductive polymer or copolymer and an organic solvent wettable fluorinated acid polymer. Electrically conductive polymer materials are derived from thiophene, pyrrole, aniline and polycyclic heteroaromatic precursor monomers. Non-conductive polymers derived from alkenyl, alkynyl, arylene, and heteroarylene precursor monomers. The organic-solvent wettable fluorinated acid polymer is fluorinated or highly fluorinated and may be colloid-forming. Acidic groups include carboxylic acid groups, sulfonic acid groups, sulfonimide groups, phosphoric acid groups, phosphonic acid groups, and combinations thereof. The compositions can be used in organic electronic devices.
189 citations
TL;DR: The broad scope of this method with respect to the alpha-olefin, carboxylic acid, and aryl boronic acid enables the rapid assembly of densely functionalized fragments for complex molecule synthesis from cheap, abundant hydrocarbon starting materials.
Abstract: A Pd(II)/sulfoxide-catalyzed sequential allylic C−H oxidation/vinylic C−H arylation of α-olefins to furnish E-arylated allylic esters in high regio- and E:Z selectivities (>20:1) is reported. The broad scope of this method with respect to the α-olefin, carboxylic acid, and aryl boronic acid enables the rapid assembly of densely functionalized fragments for complex molecule synthesis from cheap, abundant hydrocarbon starting materials. The Pd(II)/sulfoxide-catalyzed vinylic C−H arylation of electronically unbiased olefins with aryl boronic acids proceeds under oxidative, acidic conditions and mild temperatures (room temperature to 45 °C).
TL;DR: In this study, citric acid or acetic acid at higher concentrations had the greatest improvement of Pb(2+) desorption, followed by malic acid; and the smallest was oxalic acid.
TL;DR: In this paper, Takanabe et al. established a bifunctional mechanism for steam reforming of acetic acid, where both Pt and ZrO2 participate in the reaction.
TL;DR: In this article, the Eley-Rideal pathway of liquid phase esterification of C3 and C4 alcohols on acetic acid was investigated over zeolites Hβ, HY and HZSM5.
Abstract: Kinetic studies on the liquid phase esterification of C3 and C4 alcohols on acetic acid were carried out over zeolites Hβ, HY and HZSM5. The aims of this study were to arrive at the reaction mechanism from the kinetic data and to investigate the effects of the type of alcohol and zeolite type on the reaction mechanism. Zeolite Hβ was found to be the most active for this reaction. The acidity of zeolite determines the extent of the esterification reaction. The esterification reaction was found to follow the Eley–Rideal pathway. Acetic acid is activated by adsorption on the zeolite acid site, which then reacts with the alcohol in the bulk to form the corresponding acetate.
TL;DR: In this article, the effects of the crosslinker degree on the morphology and the loading capacity of the carboxylic acid group of the resultant polymer microspheres were investigated.
TL;DR: From the structure–antioxidant activity relationship studies performed it may be concluded that the number of phenolic groups and the type of the alkyl spacer between the carboxylic acid and the aromatic ring strongly influence the antioxidant activity.
Abstract: Eight structurally similar dihydroxy and trihydroxyphenolic acids (protocatechuic acid, 3,4-dihydroxyphenylacetic acid, hydrocaffeic acid, caffeic acid, gallic acid, 3,4,5-trihydroxyphenylacetic acid, 3-(3,4,5-trihydroxyphenyl)propanoic acid and 3-(3,4,5-trihydroxyphenyl)propenoic acid) were examined for their total antioxidant capacity (TAC). Furthermore, their ability to scavenge peroxyl radicals, generated by AAPH in liposomes, was determined. The antioxidant/pro-oxidant activity of the compounds was screened using the 2'-deoxyguanosine assay. All compounds behave as radical scavengers, with 3,4,5-trihydroxyphenylacetic acid being the most potent. Nevertheless, in the lipid peroxidation assay an inverse ranking order was observed, 3,4-dihydroxyphenylacetic acid being the most effective compound. All the dihydroxylated compounds showed a pro-oxidant behaviour leading to an increase of 50% in 8-OH-dG induction. From the structure-antioxidant activity relationship studies performed it may be concluded that the number of phenolic groups and the type of the alkyl spacer between the carboxylic acid and the aromatic ring strongly influence the antioxidant activity.
TL;DR: In the presence of chloroacetic acids, the photocatalytic hydrogen evolution and decomposition of the pollutants over Pt/TiO2 have been investigated and the effect of the concentration of monochloro ACetic acid and dichloroACetic acid on the hydrogen generation rate is consistent with a Langmuir-Hinshelwood kinetic model.
TL;DR: The position of the carboxylic acid group on the pyrrolidine ring directs the stereoselection of the catalyzed reaction, providing either syn- or anti-Mannich products.
Abstract: We report the development of direct catalytic, enantioselective, anti-selective Mannich-type reactions between unmodified ketones and α-imino esters under mild conditions. The reactions were performed using 5−10 mol % of (R)-3-pyrrolidinecarboxylic or (R)-β-proline as catalyst in an environmentally benign solvent, 2-PrOH, at room temperature. The anti-Mannich products were obtained in good yields with high diastereo- and enantioselectivities (up to anti/syn >99:1, 99% ee). While (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid is an excellent catalyst for the anti-Mannich-type reactions of aldehydes, it did not efficiently catalyze the corresponding Mannich-type reactions of ketones; (R)-3-pyrrolidinecarboxylic acid did efficiently catalyze the Mannich-type reactions of ketones. (S)-Proline or (S)-2-pyrrolidinecarboxylic acid has been reported to catalyze the Mannich-type reactions of ketones to afford the syn-products. Thus, the position of the carboxylic acid group on the pyrrolidine ring directs the stere...
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) was used to quantify the concentrations of hydroxyl, carboxylic acid, and carbonyl groups on carbonaceous surfaces, specifically black carbons.
Abstract: X-ray photoelectron spectroscopy (XPS) in conjunction with chemical derivatization has been developed to quantify the concentrations of hydroxyl, carboxylic acid, and carbonyl groups on carbonaceous surfaces, specifically black carbons (BCs). Control studies on polymers and graphite were performed to establish the selectivity and stoichiometry of each derivatization reaction toward the targeted oxide. Hydroxyl groups were successfully derivatized with trifluoroacetic anhydride. Derivatization strategies using trifluoroethanol, however, had to be modified from protocols used in polymer studies in order to effectively derivatize carboxylic acid groups on BCs. Derivatizing agents previously used to target carbonyl groups on polymers were found unsuitable for BC materials because of nonspecific adsorption interactions between the phenyl ring of the derivatizing agent and the extended graphene sheets of the BCs. These complications were overcome by employing trifluoroethyl hydrazine as a new derivatizing agent...
TL;DR: In this article, the authors used a capillary GC and GC-MS method to study the urban aerosol samples collected from the Hong Kong roadside atmosphere during winter and summer of 2003.
TL;DR: A simple method is presented for further optimization of initial hits by combining the mutational changes obtained from two different libraries in the combinatorial active-site saturation test.
Abstract: In a previous paper, the combinatorial active-site saturation test (CAST) was introduced as an effective strategy for the directed evolution of enzymes toward broader substrate acceptance. CASTing comprises the systematic design and screening of focused libraries around the complete binding pocket, but it is only the first step of an evolutionary process because only the initial libraries of mutants are considered. In the present study, a simple method is presented for further optimization of initial hits by combining the mutational changes obtained from two different libraries. Combined lipase mutants were screened for hydrolytic activity against six notoriously difficult substrates (bulky carboxylic acid esters) and improved mutants showing significantly higher activity were identified. The enantioselectivity of the mutants in the hydrolytic kinetic resolution of two substrates was also studied, with the best mutant-substrate combination resulting in a selectivity factor of E=49. Finally, the catalytic profile of the evolved mutants in the hydrolysis of simple nonbranched carboxylic acid esters, ranging from acetate to palmitate, was studied for theoretical reasons.
TL;DR: In this paper, a metal oxide catalyst, MgO has been developed and its effectiveness in catalyzing decarboxylation reactions involving carboxylic acid compounds such as naphthoic acid has been determined based on the formation of CO 2 and the conversion of acid.
Abstract: Naphthenic acid (NA) has been recognized as one of the major sources of corrosion in oil production and refining. In this study, catalytic decarboxylation of carboxylic acid model compounds and naphthenic acid removal from crude oil were investigated. A metal oxide catalyst, MgO has been developed and its effectiveness in catalyzing decarboxylation reactions involving carboxylic acid compounds such as naphthoic acid has been determined based on the formation of CO 2 and the conversion of acid. The major reaction takes place in the temperature range of 150–300 °C. The role of MgO in the system is considered to be multiple. It has the ability to adsorb acidic compounds via acid–base neutralization and it can also promote reactions such as decarboxylation and hydrocarbon cracking at the increased temperature. Direct application of MgO to crude oil results in significant naphthenic acid removal and lower total acidity of the oil as evidenced by a decrease in RC OOH concentration as determined by FT-IR and a lower total acid number (TAN).
TL;DR: Structural modifications to the original screening hit yielded compounds with a 100-fold increase in potency at the human GPR40 receptor and pEC(50)s in the low nanomolar range that may prove useful in unraveling the therapeutic potential of this receptor for the treatment of Type 2 diabetes.
TL;DR: The palladium acetate-catalyzed coupling reaction of aryl boronic acid with carboxylic anhydride or acyl chloride was carried out smoothly in water in the presence of poly(ethylene glycol) or 1-butyl-3-methylimidazolium hexafluorophosphate to give high yields of ketones without the use of phosphine ligands.
Abstract: The palladium acetate-catalyzed coupling reaction of aryl boronic acid with carboxylic anhydride or acyl chloride was carried out smoothly in water in the presence of poly(ethylene glycol) (PEG) or 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) to give high yields of ketones without the use of phosphine ligands. The Pd(OAc)2−H2O−[bmim][PF6] catalytic system can be recovered and reused eight times with high efficiency for both carboxylic anhydride and acyl chloride.
TL;DR: An overview of the results of organotin-NSAIDs interactions is given in this paper, where several organotin complexes with NSAIDs, derivatives of the carboxylic acid family and oxicam family have been synthesized and characterized by spectroscopy and X-ray crystallography at the University of Ioannina.
TL;DR: The carboxylic acid catalyzed three-component aza-Friedel-Crafts reactions of aldehydes, primary amines, and indoles in water have been developed and offers a novel efficient method for the synthesis of 3-substituted indoles.
TL;DR: A combination of crossover experiments and theoretical calculations has revealed that the rate- and selectivity-determining step is ring closure, not betaine formation as was the case for phenyl-stabilized ylides.
Abstract: The reactions of a range of amide-stabilized sulfur ylides derived from readily available camphor-derived sulfonium salts for the synthesis of glycidic amides have been studied. Primary, secondary, and tertiary amides were tested, and it was found that the highest enantioselectivities were observed with tertiary amides, which provided glycidic amides in good to excellent yields, exclusive trans selectivity, and excellent enantioselectivities. The reaction was general for aromatic aldehydes, but aliphatic aldehydes gave more variable enantioselectivities. The epoxy amides could be converted cleanly into epoxy ketones by treatment with organolithium reagents. We were also able to effect selective ring opening of the epoxy amides with a variety of nucleophiles, followed by hydrolysis of the amide to yield the corresponding carboxylic acid. This methodology was applied to the total synthesis of the target compound SK&F 104353. A combination of crossover experiments and theoretical calculations has revealed that the rate- and selectivity-determining step is ring closure, not betaine formation as was the case for phenyl-stabilized ylides.
TL;DR: Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO(2-x)N(x) surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes.
Abstract: We report the photooxidation of toluene over nitrogen doped TiO2 (TiO2−xNx) under visible light irradiation. The photocatalytic oxidation of toluene in air over TiO2−xNx powders was studied using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), gas chromatography (GC), ion chromatography (IC), and gas chromatography mass spectrometry (GC-MS), focusing on the photocatalytic decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the catalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO2−xNx surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. No gaseous intermediates were detected during the photooxidation. Major intermediates adsorbed at the catalyst surface were oxalic acid, (COOH)2, acetic acid, CH3COOH, formic acid, HCOOH, and pyruvic acid, CH3COCOOH, whereas more complicated carboxylic species, including propionic acid, CH3CH2COOH, isovaleric acid, (CH3)2CHCH2COOH, and succinic acid, (CH2COOH)2, were also found in the early stage of the photooxidation. These intermediate products were gradually photodegraded to CO2 and H2O under visible light irradiation.
TL;DR: In this paper, a redox-responsive hydrogel system was constructed by combining β-cyclodextrin (β-CD), dodecyl-modified poly(acrylic acid), and fenocenecarboxylic acid (FCA).
Abstract: We have successfully constructed a redox-responsible hydrogel system by combination of β-cyclodextrin (β-CD), dodecyl-modified poly(acrylic acid) [p(AA/ C 12 )], and a redox-responsive guest, fenocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel-like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.
TL;DR: The tetrabutylammonium-induced liquid-liquid-phase separation in alkyl carboxylic acid vesicular solutions for the extraction of organic compounds prior to liquid chromatography was examined for the first time and the coacervates were compatible with the chromatographic determination of analytes following UV or MS detection.
Abstract: The potential of the tetrabutylammonium-induced liquid−liquid-phase separation in alkyl carboxylic acid vesicular solutions for the extraction of organic compounds prior to liquid chromatography was examined for the first time. The behavior of the coacervates yielded from octanoic to oleic acids as a function of the pH and salts was investigated. The time required for phase separation depended on the length of the carboxylic acid alkyl chain and the experimental procedure (i.e., standing, sonication, centrifugation, stirring, etc.). Theoretical preconcentration factors were a function of both surfactant concentration and the length of the alkyl chain, and they greatly surpassed those obtained with other surfactant-mediated separations (e.g., surfactant-rich phases from dodecanesulfonic acid or Triton X-114). Parameters affecting the extraction efficiency were assessed. Analytes in a wide polarity/charge range, (e.g., PAHs, surfactants, chlorophenols, bisphenols, phthalates, herbicides, amines, dyes, and p...