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Showing papers on "Carboxylic acid published in 2009"


Journal ArticleDOI
TL;DR: The photolysis of S(2)O(8)(2-) was studied for the removal of acetic acid in aqueous solution and compared with the H2O(2)/UV system, suggesting that above this pH, competitive reactions with the carbon mineralized inhibit the reaction of the solute with SO(4)(-) and also ()OH radicals.

270 citations


Journal ArticleDOI
TL;DR: It is demonstrated for the first time that the ESDPT reaction can take place between 2AP and all of these acids due to the formation of the intermolecular double hydrogen bonds.
Abstract: In the present work, the excited-state double proton transfer (ESDPT) in 2-aminopyridine (2AP)/acid systems has been reconsidered using the combined experimental and theoretical methods. The steady-state absorption and fluorescence spectra of 2AP in different acids, such as formic acid, acetic acid, propionic acid, etc. have been measured. We demonstrated for the first time that the ESDPT reaction can take place between 2AP and all of these acids due to the formation of the intermolecular double hydrogen bonds. Furthermore, the vitally important role of the intermolecular double hydrogen bonds between 2AP and acids for ESDPT reaction has also been confirmed by the disappearance of ESDPT when we add the polar acetonitrile to the 2AP/acids systems. This may be due to that the respective polar solvation of 2AP and acids by the acetonitrile solvent disrupts the formation of intermolecular double hydrogen bonds between 2AP and acids. Moreover, the intermolecular double hydrogen bonds are demonstrated to be significantly strengthened in the electronic excited state of 2AP/acid systems using the time-dependent density functional theory (TDDFT) method. The ESDPT reaction is facilitated by the electronic excited-state hydrogen bond strengthening. In addition, potential energy curves of the electronic excited state along the proton transfer coordinate are also calculated by the TDDFT method. The stepwise mechanism of the ESDPT reaction in the 2AP/acid systems is theoretically reconfirmed, and the concerted mechanism is theoretically excluded. At the same time, the sequence of the double proton transfers is theoretically clarified for the first time using the potential energy curves calculated by TDDFT method.

204 citations


Journal ArticleDOI
TL;DR: Increased carboxylic acid content within NA structures of higher MW decreases hydrophobicity and, consequently, offers a plausible explanation as to why lower MW NAs in oil sands process-affected water are more toxic than the greaterMW NAs.
Abstract: Fractions of methylated naphthenic acids (NAs) isolated from oil sands process-affected water were collected utilizing Kugelrohr distillation and analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. 1H NMR analysis revealed that the ratio of methyl ester hydrogen atoms to remaining aliphatic hydrogen atoms increased from 0.130 to 0.214, from the lowest to the greatest molecular weight (MW) fractions, respectively, indicating that the carboxylic acid content increased with greater MW. Acute toxicity assays with exposure to monocarboxyl NA-like surrogates demonstrated that toxicity increased with increasing MW (D. magna LC50 values of 10 ± 1.3 mM and 0.59 ± 0.20 mM for the respective lowest and highest MW NA-like surrogates); however, with the addition of a second carboxylic acid moiety, the toxicity was significantly reduced (D. magna LC50 values of 10 ± 1.3 mM and 27 ± 2.2 mM for the respective monocarboxyl and dicarboxyl NA-like surrogates of similar MW). Increased carboxylic acid content...

192 citations


Journal ArticleDOI
TL;DR: In this paper, reaction kinetics studies were carried out using hexanoic acid, as a representative carboxylic acid, in the presence of 1-pentanol and 2-butanone, as representative biomass-derived alcohol and ketone species.

180 citations


Journal ArticleDOI
TL;DR: The present coupling procedure is applicable to the synthesis of other various heteroarenes possessing di-, tri-, and tetracyclic cores and some of the products exhibit intense fluorescence in the solid state.
Abstract: The selective synthesis of 1,2,3,4-tetrasubstituted carbazoles can be performed effectively through the palladium-catalyzed oxidative coupling reactions of N-substituted indoles or their carboxylic acid derivatives with alkynes. Unsymmetrically octasubstituted carbazoles can also be obtained by the stepwise couplings of 1-methylpyrrole-2-carboxylic acid with two different alkynes. In addition, the present coupling procedure is applicable to the synthesis of other various heteroarenes possessing di-, tri-, and tetracyclic cores. Some of the products exhibit intense fluorescence in the solid state.

177 citations


Journal ArticleDOI
TL;DR: The direct oxidative coupling of 2-amino- and 2-hydroxybenzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding 8-substituted isocoumarin derivatives, some of which exhibit solid-state fluorescence.
Abstract: The direct oxidative coupling of 2-amino- and 2-hydroxybenzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding 8-substituted isocoumarin derivatives, some of which exhibit solid-state fluorescence. Depending on conditions, 4-ethenylcarbazoles can be synthesized selectively from 2-(arylamino)benzoic acids. The oxidative coupling reactions of heteroarene carboxylic acids as well as aromatic diacids with an alkyne are also described.

171 citations


Journal ArticleDOI
01 Apr 2009-Langmuir
TL;DR: A novel set of amphiphilic dipeptide-based carboxylic acids capable of efficiently gelating organic solvents with pH responsiveness was reported, which was aptly utilized for the pH-dependent phase-selective gelation of either solvent in a biphasic mixture of oil and water.
Abstract: The search for efficient low-molecular-weight gelators (LMWGs) with possible structure−activity correlation is on the rise The present work reports a novel set of amphiphilic dipeptide-based carboxylic acids capable of efficiently gelating organic solvents More interestingly, their sodium salts showed enhanced efficiency in organogelation with the additional ability to gelate water Electrostatic interactions present in the aggregation of the sodium carboxylates of amphiphilic dipeptides seem to be important because some of the nongelator carboxylic acids turned out to be excellent gelators upon salt formation The combinations and sequence of the amino acids in the dipeptide moiety were systematically altered to understand the collective importance of the nonpolar aliphatic/aromatic substitution in amino acids in the self-assembling behavior of amphiphiles Almost a 20-fold enhancement in the gelation ability was observed on reversing the sequence of the amino acid residues, and in some cases, nongelat

167 citations


Journal ArticleDOI
TL;DR: In this article, a review of the conversion of lactic acid to other important commodity chemicals, such as poly L•lactic acid, acrylic acid, 2, 3•pentanedione, pyruvic acid, propanoic acid, 1, 2•propanediol, acetaldehyde, ethyl lactate, using chemical or biological catalysts, and the economy analysis of conversions are depicted.
Abstract: Owning to its biobased organic acid, low cost and multiple reactive functionalities as it contains both one carboxylic acid group and hydroxyl group, lactic acid has been described as a commodity chemical sleeping giant. In this review, the conversion of lactic acid to other important commodity chemicals, such as, poly L‐lactic acid, acrylic acid, 2, 3‐pentanedione, pyruvic acid, propanoic acid, 1, 2‐propanediol, acetaldehyde, ethyl lactate, using chemical or biological catalysts, and the economy analysis of conversions are depicted. The conversion would provide a new way for the solution of the present oil crisis.

167 citations


Journal ArticleDOI
TL;DR: In this article, 13 new multicomponent crystals (cocrystals and salts) of an anticonvulsant drug gabapentin with various carboxylic acid coformers have been discovered using the reaction crystallization method.
Abstract: Thirteen new multicomponent crystals (cocrystals and salts) of an anticonvulsant drug gabapentin with various carboxylic acid coformers have been discovered using the reaction crystallization method (RCM). These new forms are characterized by X-ray powder diffraction (XRPD), Raman and infrared spectroscopy, and differential scanning calorimetry (DSC). Crystal structures with 3-hydroxybenzoic acid (3HBA) 1, 4-hydroxybenzoic acid (4HBA) 2, salicylic acid 3, 1-hydroxy-2-napthoic acid (1H2NA) 4, and RS-mandelic acid 5 are also determined. While there is proton transfer from coformer to gabapentin in crystals 3−5, no proton transfer occurs in 1. Partial proton transfer is observed in crystal structure 2. Multicomponent crystals 1−5 are thermodynamically stable and do not transform to gabapentin hydrate in water suggesting that the multicomponent phases have equal or lower solubility than the components. pH has been shown to be an important variable in controlling solubility and stability. A mathematical model ...

160 citations


Journal ArticleDOI
TL;DR: 33 carboxylic acid derivatives were tested and caffeic acid derivatives such as chlorogenic acid and curcumin were found to be highly potent compared to sodium butyrate, which is a well-known HDAC inhibitor.

154 citations


Journal ArticleDOI
TL;DR: It was found that even after exhaustive washing with aqueous base the purified SWNTs contain carboxylic acid groups in sufficient quantity to prepare high quality soluble SWNT materials by covalent functionalization with octadecylamine.
Abstract: We report an investigation of the nature and chemical functionalization of nitric acid treated single-walled carbon nanotubes (SWNTs). SWNTs washed with diluted sodium hydroxide solutions were characterized by near-IR, mid-IR, and Raman spectroscopy as well as TEM, and the remaining carboxylic acid content was determined to assess the effect of base washing on the removal of carboxylated carbon fractions, which are generated by the nitric acid treatment. It was found that even after exhaustive washing with aqueous base the purified SWNTs contain carboxylic acid groups in sufficient quantity to prepare high quality soluble SWNT materials by covalent functionalization with octadecylamine.

Journal ArticleDOI
11 Mar 2009-Langmuir
TL;DR: Correlations of these LMOG structures (as well as with those that lack a hydroxyl group along the n-alkyl chain, a headgroup at its end, or both) with the properties of their gels, coupled with the unusual theological properties of these systems, point to new directions for designing LMOGs and organogels.
Abstract: Thirteen members of a new class of low molecular-mass organogelators (LMOGs), amides, and amines based on (R)-12-hydroxystearic acid (HSA; i.e., (R)-12-hydroxyoctadecanoic acid) and the properties of their gels have been investigated by a variety of structural and thermal techniques. The abilities of these LMOGs, molecules with primary and secondary amide and amine groups and the ammonium carbamate salt of 1-aminooctadecan-12-ol, to gelate a wide range of organic liquids have been ascertained. Their gelating efficiencies are compared with those of HSA and the corresponding nitrogen-containing molecules derived from stearic acid (i.e., HSA that lacks a 12-hydroxyl group). Several of the HSA-derived molecules are exceedingly efficient LMOGs, with much less than 1 wt % being necessary to gelate several organic liquids at room temperature. Generally, the self-assembled fibrillar networks of the gels consist of spherulitic objects whose dimensions depend on the protocol employed to cool the precursor sol phase...

Journal ArticleDOI
TL;DR: An effective protocol has been developed that allows the smooth protodecarboxylation of diversely functionalized aromatic carboxylic acids within 5-15 min.
Abstract: An effective protocol has been developed that allows the smooth protodecarboxylation of diversely functionalized aromatic carboxylic acids within 5−15 min. In the presence of at most 5 mol % of an inexpensive catalyst generated in situ from copper(I) oxide and 1,10-phenanthroline, even nonactivated benzoates were converted in high yields and with great preparative ease.

Journal ArticleDOI
TL;DR: In this paper, the authors used magnetic hyperthermia to kill Staphyloccocus aureus using three carboxylic acid functionalised organic ligands (tiopronin, oxamic acid and succinic acid) using a co-precipitation method.
Abstract: Iron oxide nanoparticles were made in the presence of three carboxylic acid functionalised organic ligands (tiopronin, oxamic acid and succinic acid) using a co-precipitation method The iron oxide was a mixture of magnetite and maghemite with an average crystallite size less than 10 nm The samples were all dialysed prior to analysis to ensure high purity Without the presence of a carboxylic acid, the dialysis purification stage invoked complete precipitation and the sample was completely intractable The carboxylic acid stabilised particles could be dissolved in water to form a stable solution The samples prepared with tiopronin and succinic acid were close to neutral pH and were suitable for magnetic fluid hyperthermia testing on Staphyloccocus aureus Iron oxide produced with tiopronin was able to achieve a 107-fold reduction in the viable count of the organism using a 2 × 2 minute exposure to an AC magnetic field and this bactericidal effect could still be achieved using the same batch of particles one week later Oxidation of the samples did occur with aging or sonication and made the heating response less effective after one month The tiopronin stabilised nanoparticles were able to achieve substantial kills of bacteria at concentrations between 625–50 mg/ml This is, to our knowledge, the first time magnetic hyperthermia has been used to kill bacteria The heating rates obtained from using an external magnetic alternating field on the iron oxide nanoparticle solutions were four times greater than the best commercially available material This novel method of killing bacteria could form the basis of a new approach to the treatment of a variety of infectious diseases

Journal ArticleDOI
TL;DR: In this paper, the deoxygenation experiments of different reactants, i.e., pure palmitic acid, stearic acid and a technical grade stearric acid containing a mixture of 59% of palmitics and 40% of stearics, were successfully performed over 4 wt% Pd/C mesoporous catalyst at 300 °C under 17 bar of 5% H2 in argon.
Abstract: The deoxygenation experiments of different reactants, ie, pure palmitic acid, stearic acid, and a technical grade stearic acid containing a mixture of 59% of palmitic and 40% of stearic acid were successfully performed over 4 wt% Pd/C mesoporous catalyst at 300 °C under 17 bar of 5% H2 in argon The main product in catalytic deoxygenation of saturated fatty acids, C16 and C18, were aliphatic chain length hydrocarbons containing one less carbon than the corresponding acid Additionally it was found that the deoxygenation rates of different reactant were independent on carbon chain length of its fatty acids

Journal ArticleDOI
TL;DR: It is argued, using density functional theory predictions and XPS of slid track, that when the molecular backbone of unsaturated fatty acids are tilted and pressed strongly by a probe, in tribological contact, the high charge density of the double bond region of the backbone allows coupling with the steel substrate.

Journal ArticleDOI
TL;DR: Evidence in several spectral regions indicates that K(+) exhibits stronger ionic binding affinity to the carboxylate anion relative to Na(+) and that various degrees of deprotonation are initiated by the introduction of Na(+) and K(+).
Abstract: Ionic binding of alkali ions Na+ and K+ to the carboxylic acid headgroups of fatty acid monolayers is studied as a proxy toward understanding the fundamental chemistry in cell biology. In this study, we used broad-bandwidth sum frequency generation (BBSFG) vibrational spectroscopy to investigate the ionic binding event that leads to deprotonation and complex formation of fatty acid headgroups. Palmitic acid (C15H31COOH) exists as a monolayer on aqueous surfaces. Surface vibrational stretch modes of palmitic acid from 1400 cm−1 to 3700 cm−1 were observed (νs-COO−, ν-C═O, ν-C—H, ν-O—H of —COOH, free OH). Palmitic acid is mostly protonated at the aqueous surface at neutral pH (∼6). However, various degrees of deprotonation are initiated by the introduction of Na+ and K+ that results in the complexation of K+:COO− and solvent separated Na+:COO−. Evidence in several spectral regions indicates that K+ exhibits stronger ionic binding affinity to the carboxylate anion relative to Na+.

Journal ArticleDOI
Walt Partenheimer1
TL;DR: The authors showed that the presence of phenolic functionality on an aromatic ring does inhibit the rate of reaction but that the alkyl group on the ring still does oxidize to the carboxylic acid, and that the masking of phenol by acetylation occurs at a reasonable rate in acetic acid.
Abstract: Roughly 30% of all woody plants is composed of lignin. Five different lignin samples from wood and bagasse, were oxidized in air with a cobalt/ manganese/zirconium/bromide (Co/Mn/Zr/Br) catalyst in acetic acid as a function of time, temperature, pressure, and lignin and catalyst concentrations. 18 products were identified via gas chromatographymass spectrometry (GC/MS). The most valuable products from lignin were 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzaldehyde (vanillin), 4-hydroxy-3-methoxybenzoic acid (vanillic acid), 4-hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde) and 4-hydroxy-3,5-dimethoxybenzoic acid (syringic acid). 10.9wt% of the lignin was converted to the aromatic products. By the use of model compounds we demonstrate that 1) the presence of the phenolic functionality on an aromatic ring does inhibit the rate of reaction but that the alkyl group on the ring still does oxidize to the carboxylic acid, 2) that the masking of phenol by acetylation occurs at a reasonable rate in acetic acid, 3) that the alkyl group of the masked phenol does very readily oxidize, 4) that an acetic anhydride/acetic acid mixture is a good oxidation solvent and 5) that a two-step acetylation/oxidation to the carboxylic acid is feasible.

Journal ArticleDOI
TL;DR: In this article, structural isomers of aromatic carboxylic acids with additional hydrogen-bonding functional groups (i.e., hydroxy group) were screened for cocrystal formation, and nine new solid phases involving caffeine were identified using single-crystal X-ray diffraction and FT-IR spectroscopy.
Abstract: Caffeine, a pharmaceutical model compound, generally forms cocrystals with carboxylic acids that involve an O−H···N hydrogen bond between the carboxylic acid group of the acid and the caffeine imidazole moiety. Such solids are typically based on a single heterosynthon. To examine the facility of introducing additional supramolecular heterosynthons to the caffeine-carboxylic-acid cocrystal system, structural isomers of aromatic carboxylic acids (i.e., hydroxy- and dihydroxybenzoic acids) with additional hydrogen-bonding functional groups (i.e., hydroxy group) were screened for cocrystal formation. For this purpose, a highly efficient screening method based on thermodynamically driven solution-mediated phase transformation was utilized. This method enabled the rapid discovery of nine new solid phases involving caffeine. These caffeine phases were identified using single-crystal X-ray diffraction and FT-IR spectroscopy as cocrystals based on 2-, 3-, 4-hydroxybenzoic- and 2,3-, 2,4-, 2,5-, 3,4-, and 3,5-dihyd...

Journal ArticleDOI
TL;DR: In this paper, a series of catalysts containing 5-30-wt% of 12-tungstophosphoric acid (TPA) supported on niobia were prepared and their catalytic activity was evaluated for esterification of free fatty acids with methanol.
Abstract: A series of catalysts containing 5–30 wt% of 12-tungstophosphoric acid (TPA) supported on niobia were prepared and their catalytic activity was evaluated for esterification of free fatty acids with methanol. The catalysts were characterized by FT-infrared spectroscopy, X-ray diffraction and temperature programmed desorption of ammonia. The esterification activity depends on the content of TPA on niobia; the catalyst with 25 wt% of TPA exhibited highest activity. The best catalyst was subjected to different calcination temperatures to study the structural changes. We observed that esterification activity depends upon the structural variations of the catalyst. The effects of reaction variables such as catalyst loading, methanol to acid ratio, reaction time and temperature on the conversion of fatty acid were studied. The esterification activity of the catalysts is correlated with the characteristics of the catalysts.

Journal ArticleDOI
TL;DR: A convenient and clean procedure of esterification is reported by direct condensation of equimolar amounts of carboxylic acids with alcohols catalyzed by an easy to prepare catalyst system of perchloric acid immobilized on silica gel.
Abstract: A convenient and clean procedure of esterification is reported by direct condensation of equimolar amounts of carboxylic acids with alcohols catalyzed by an easy to prepare catalyst system of perchloric acid immobilized on silica gel (HClO4−SiO2). The direct condensation of aryl, heteroaryl, styryl, aryl alkyl, alkyl, cycloalkyl, and long-chain aliphatic carboxylic acids with primary/secondary alkyl/cycloalkyl, allyl, propargyl, and long-chain aliphatic alcohols has been achieved to afford the corresponding esters in excellent yields. Chiral alcohol and N-t-Boc protected chiral amino acid also resulted in ester formation with the representative carboxylic acid or alcohol without competitive N-t-Boc deprotection and detrimental effect on the optical purity of the product demonstrating the mildness and chemoselectivity of the procedure. The esters of long-chain (>C10) acids and alcohols are obtained in high yields. The catalyst is recovered and recycled without significant loss of activity. The industrial a...

Journal ArticleDOI
TL;DR: The results show that carboxylic acids play an essential role in the host-seeking behavior of An.
Abstract: The role of aliphatic carboxylic acids in host-seeking response of the malaria mosquito Anopheles gambiae sensu stricto was examined both in a dual-choice olfactometer and with indoor traps. A basic attractive blend of ammonia + lactic acid served as internal standard odor. Single carboxylic acids were tested in a tripartite blend with ammonia + lactic acid. Four different airflow stream rates (0.5, 5, 50, and 100 ml/min) carrying the compounds were tested for their effect on trap entry response in the olfactometer. In the olfactometer, propanoic acid, butanoic acid, 3-methylbutanoic acid, pentanoic acid, heptanoic acid, octanoic acid, and tetradecanoic acid increased attraction relative to the basic blend. While several carboxylic acids were attractive only at one or two flow rates, tetradecanoic acid was attractive at all flow rates tested. Heptanoic acid was attractive at the lowest flow rate (0.5 ml/min), but repellent at 5 and 50 ml/min. Mixing the air stream laden with these 7 carboxylic acids together with the headspace of the basic blend increased attraction in two quantitative compositions. Subtraction of single acids from the most attractive blend revealed that 3-methylbutanoic acid had a negative effect on trap entry response. In the absence of tetradecanoic acid, the blend was repellent. In assays with MM-X traps, both a blend of 7 carboxylic acids + ammonia + lactic acid (all applied from low density polyethylene-sachets) and a simple blend of ammonia + lactic acid + tetradecanoic acid were attractive. The results show that carboxylic acids play an essential role in the host-seeking behavior of An. gambiae, and that the contribution to blend attractiveness depends on the specific compound studied.

Journal ArticleDOI
TL;DR: In this paper, the water tolerance properties of SBA-15 materials were investigated in detail, and the results showed that the functionalized mesoporous materials demonstrated a comparable site activity to H2SO4 in acetic acid esterification proving its potential for application.
Abstract: Esterification of acetic acid with methanol, which was used as a model reaction in the stabilization of bio-oil, was tested over propylsulfonic acid-functionalized SBA-15 materials. Due to the significant amount of water content in bio-oil, the water tolerance properties of the materials were also investigated in detail. The results showed that the functionalized mesoporous materials demonstrated a comparable site activity to H2SO4 in acetic acid esterification proving its potential for application. The effect of propylsulfonic acid loading showed that the intrinsic per site activity increased with the number of acid sites, which suggested the presence of acidic site cooperativity. Water tolerance experiments showed that SO3H-SBA-15 exhibited less reaction inhibition due to water than did H2SO4, which was at least partially ascribed to the hydrophobic propyl groups bonded to sulfonic acid groups. Further functionalization of SO3H-SBA-15 with hydrophobic propyl groups further increased the water tolerance property of the catalyst in the esterification reaction. The reusability of the catalyst was also investigated and showed multiple cycle stability for acetic acid esterification without significant loss of activity.

Journal ArticleDOI
TL;DR: The synthesis and the detailed structure-activity relationship of the quinolone carboxylic acids are shown as a novel monoketo acid class of integrase inhibitors and Elvitegravir 49 was chosen as a candidate for further studies and is currently in phase 3 clinical trials.
Abstract: Human immunodeficiency virus type 1 (HIV-1) integrase is a crucial target for antiretroviral drugs, and several keto-enol acid class (often referred to as diketo acid class) inhibitors have clinically exhibited marked antiretroviral activity. Here, we show the synthesis and the detailed structure-activity relationship of the quinolone carboxylic acids as a novel monoketo acid class of integrase inhibitors. 6-(3-Chloro-2-fluorobenzyl)-1-((2S)-1-hydroxy-3,3-dimethylbutan-2-yl)-7-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 51, which showed an IC50 of 5.8 nM in the strand transfer assay and an ED50 of 0.6 nM in the antiviral assay, and 6-(3-chloro-2-fluorobenzyl)-1-((2S)-1-hydroxy-3-methylbutan-2-yl)-7-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 49, which had an IC50 of 7.2 nM and an ED50 of 0.9 nM, were the most potent compounds in this class. The monoketo acid 49 was much more potent at inhibiting integrase-catalyzed strand transfer processes than 3'-processing reactions, as is the case with the keto-enol acids. Elvitegravir 49 was chosen as a candidate for further studies and is currently in phase 3 clinical trials.

Journal ArticleDOI
TL;DR: Chitosan-TGA/oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.

Journal ArticleDOI
TL;DR: In this paper, an effective catalytic system comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) functionalized imidazolium salt, a carboxylic acid substituted IMIDAZOLium salt ([Imim-COOH] + X - ), and sodium nitrite (NaNO 2 ) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to >
Abstract: An effective catalytic system comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) functionalized imidazolium salt ([Imim-TEMPO] + X - ), a carboxylic acid substituted imidazolium salt ([Imim-COOH] + X - ), and sodium nitrite (NaNO 2 ) was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with excellent selectivity up to > 99%, even at ambient conditions. Notably, the catalyst system could preferentially oxidize a primary alcohol to the aldehyde rather than a secondary alcohol to the ketone. Moreover, the reaction rate is greatly enhanced when a proper amount of water is present. And a high turnover number (TON 5000) is achieved in the present transition metal-free aerobic catalytic system. Additionally, the functionalized imidazolium salts are successfully reused at least four times. This process thus represents a greener pathway for the aerobic oxidation of alcohols into carbonyl compounds by using the present task-specific ionic liquids in place of the toxic and volatile additive, such as hydrogen bromide, bromine, or hydrogen chloride (HBr, Br 2 or HCl), which is commonly required for the transition metal-free aerobic oxidation of alcohols.

Journal ArticleDOI
TL;DR: In this research, gliadin, soyprotein, and zein fibers have been crosslinked with malic acid, citric acid, and butanetetracarboxylic acid to improve the tenacity of the fibers without using high temperatures and phosphorus‐containing catalysts.
Abstract: We report the development of a new method of alkali-catalyzed low temperature wet crosslinking of plant proteins to improve their breaking tenacity without using high temperatures or phosphorus-containing catalysts used in conventional poly(carboxylic acid) crosslinking of cellulose and proteins. Carboxylic acids are preferred over aldehyde-containing crosslinkers for crosslinking proteins and cellulose because of their low toxicity and cost and ability to improve the desired properties of the materials. However, current knowledge in carboxylic acid crosslinking of proteins and cellulose requires the use of carboxylic acids with at least three carboxylic groups, toxic phosphorous-containing catalysts and curing at high temperatures (150-185 degrees C). The use of high temperatures and low pH in conventional carboxylic acid crosslinking has been reported to cause substantial strength loss and/or undesired changes in the properties of the crosslinked materials. In this research, gliadin, soy protein, and zein fibers have been crosslinked with malic acid, citric acid, and butanetetracarboxylic acid to improve the tenacity of the fibers without using high temperatures and phosphorus-containing catalysts. The new method of wet crosslinking using carboxylic acids containing two or more carboxylic groups will be useful to crosslink proteins for various industrial applications.

Journal ArticleDOI
TL;DR: It was found that there is a slight increase in the amount of B-N dative bonding on going from a tertiary to a secondary to a primary amine group, but that solvent insertion dominates in all cases of the boronate esters.
Abstract: This work investigates the interplay between the intramolecular B-N dative bonding and solvent insertion in various ortho-methylamino arylboronic acids in protic media. (11)B NMR experiments were conducted to study the effect that the degree of substitution of the amine group has on B-N bonding versus solvent insertion. It was found that there is a slight increase in the amount of B-N dative bonding on going from a tertiary to a secondary to a primary amine group, but that solvent insertion dominates in all cases of the boronate esters. A X-ray crystal structure gives further insight into the structure of the solvent-inserted boronate esters, showing that the inserted solvent has its hydrogen primarily on the amine. Lastly, studies of the use of boronate esters as receptors for simple alcohols and carboxylic acids are described.

Journal ArticleDOI
TL;DR: Compound 9d with an alkene linker was found to be both more metabolically stable and more potent than compound 3, with a minimum inhibitory concentration of 0.2 microM against replicating and nonreplicating Mycobaterium tuberculosis.
Abstract: Both in vitro and in vivo metabolism studies suggested that 5-(2,8-bis(trifluoromethyl)quinolin-4-yloxymethyl)isoxazole-3-carboxylic acid ethyl ester (compound 3) with previously reported antituberculosis activity is rapidly converted to two metabolites 3a and 3b. In order to improve the metabolic stability of this series, chemistry efforts were focused on the modification of the oxymethylene linker of compound 3 in the present study. Compound 9d with an alkene linker was found to be both more metabolically stable and more potent than compound 3, with a minimum inhibitory concentration (MIC) of 0.2 microM and 2.6 microM against replicating and nonreplicating Mycobaterium tuberculosis, respectively. These attributes make 9d an interesting lead compound. A number of modifications were made to the structure of 9d, and a series of active compounds were discovered. Although some neurotoxicity was observed at a high dosage, this new series was endowed with both improved in vitro anti-TB activity and metabolic stability in comparison to compound 3.

Journal ArticleDOI
TL;DR: Mesoporous TiO2 photocatalysts have been synthesized in acetic acid aqueous solutions by using the amphiphilic triblock copolymer (Pluronic P123) template as discussed by the authors.