Carboxylic Acid Functional Groups Research Articles

Impact of Carboxyl Groups in Graphene Oxide on Chemoselective Alcohol Oxidation with Ultra-Low Carbocatalyst Loading

A highly efficient and simple chemoselective aerobic oxidation of primary alcohols to either aldehydes or carboxylic acids in the presence of nitric acid was developed, utilising 5 wt% graphene oxide as a carbocatalyst under ambient reaction conditions. Carboxylic acid functional groups on graphene oxides played a vital role in carbocatalyst activity, greatly influencing both the reactivity and selectivity. We also applied this protocol to a variant of the Knoevenagel condensation for primary alcohols and malonates with a secondary amine co-catalyst via cooperative catalysis.

Bifunctional Cage-Type Cubic Mesoporous Silica SBA-1 Nanoparticles for Selective Adsorption of Dyes.

Bifunctional SBA-1 mesoporous silica nanoparticles (MSNs) with carboxylic acid and amino groups (denoted as CNS-10-10) have been successfully synthesized, characterized, and employed as adsorbents for dye removal. Adsorbent CNS-10-10 shows high affinity towards cationic and anionic dyes in a wide pH range, and exhibits selective dye removal of a two-dye mixture system of cationic methylene blue and anionic eosin Y. By changing the pH of the medium, the selectivity of the adsorption behavior can be easily modulated. For comparison purposes, the counterparts, that is, pure silica SBA-1 MSNs (CS-0) and those with either carboxylic acid or amino functional groups (denoted as CS-10 and NS-10, respectively) were also prepared to evaluate their dye-adsorption behaviors. As revealed by the zeta-potential measurements, the electrostatic interaction between the adsorbent surface and the dye molecule plays an important role in the adsorption mechanism. Adsorbent CNS-10-10 can be easily regenerated and reused, and maintains its adsorption efficiency up to 80 % after four cycles.

Chromium adsorption using waste tire and conditions optimization by response surface methodology

Chromium adsorption was investigated using waste tire adsorbent (WTA) and the process variables (pH, adsorbent dosage, Cr ions initial concentration, contact time) were optimized through response surface methodology. Initial metal ions concentration (20–820mg/L), pH (1.0–9.0 for Cr(VI) and 1.0–5.0 for Cr(III)), contact time (288–1440min) and adsorbent dose (0.1–2.1g/100mL) were selected and optimized as experimental variables, which affected the Cr adsorption significantly. The optimum conditions for maximum Cr(VI) adsorption were found as; 336.63mg/L initial concentration, pH 4.8, contact time 882.5min, whereas for Cr(III), the optimum levels of process variables were 1.2g/100mL and 337mg/L, 3.0, 910.18min and 1.3g/100mL solution, respectively. The sorption capacities were 105.84 and 174.55mg/g for Cr(VI) and Cr(III), respectively. At optimized conditions, 79.6% (214.72mg/g) Cr was sequestered from tannery effluents. The Langmuir isotherm and pseudo-first order kinetic model fitted well to the Cr adsorption data. The FTIR study revealed the involvement of hydroxyl, amino and carboxylic acid functional groups in the adsorption of Cr ions.

Modeling rates of DOC degradation using DOM composition and hydroclimatic variables

AbstractThe fluvial fluxes of dissolved organic carbon (DOC) from peatlands form an important part of that ecosystem's carbon cycle, contributing approximately 35% of the overall peatland carbon budget. The in‐stream processes acting on the DOC, such as photodegradation and biodegradation, can lead to DOC loss and thus contribute CO2 to the atmosphere. The aim of this study was to understand what controls the rates of DOC degradation. Water samples from a headwater, peat‐covered catchment, were collected over a 23 month period and analyzed for the DOC degradation rate and dissolved organic matter (DOM) composition in the context of hydroclimatic monitoring. Measures of DOM composition included 13C solid‐state nuclear magnetic resonance spectroscopy, bomb calorimetry, and elemental analysis. Regression analysis showed that there was a significant role for the composition of the DOM in controlling degradation with degradation rates significantly increasing with the proportion of aldehyde and carboxylic acid functional groups but decreasing with the proportion of N‐alkyl functional groups. The highest rates of DOC degradation occurred when aldehyde functionality was at its greatest and this occurred on the recession limb of storm hydrographs. Including this knowledge into models of fluvial carbon fate for an 818 km2 catchment gave an annual average DOC removal rate of 67% and 50% for total organic carbon, slightly lower than previously predicted. The compositional controls suggest that DOM is primarily being used as a ready energy source to the aquatic ecosystem rather than as a nutrient source.

Waterborne polyurethane molecular structure designed and its acetic acid and ammonia absorption efficiency

In this study, waterborne polyurethane (WPU) resins consisted of carboxylic acid and side-chained EO (ethylene oxide) functional groups were prepared via a prepolymer ion-hybrid reaction process. After dipping the WPU on fabrics, the dipped fabrics showed promising deodorization properties for both basic and acidic odors and also showed good wash durability because of the presence of those characteristic groups. Basic odors were neutralized via carboxylic acid groups on the WPU, whereas acidic odors were absorbed by the EO groups through hydrogen bonding. Fourier transform infrared spectroscopy (FT-IR) was used to examine the functional groups of carboxylic acid and EO groups, before and after dipping the WPU on the fabrics. The deodorization properties of the dipped fabrics were associated with the content of the functional groups existing on the WPU molecular chain. Scanning electron microscope (SEM) analysis also revealed that the dipped fabrics had a promising wash durability and deodorization properties after 5 times of laundering because WPU particles were still strongly adhered to the fabrics. More side-chain EO groups, more acetic acid molecules were absorbed; while more-COOH groups in polymer chain, more ammonium molecules were absorbed. Table 2 shows that the synthesized WPU’s possess very highly washed durability.

Synthesis and Bioactivity Evaluation of Novel 2-Salicyloylbenzofurans as Antibacterial Agents.

In order to discover new antibacterial agents, series of 2-salicyloylbenzofuran derivatives were designed, synthesized and evaluated for their antibacterial activities against three Gram-(+) strains (methicillin-sensitive Staphylococcus aureus (MSSA) ATCC 29213, methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, and Streptococcus faecalis (S. faecalis) ATCC 29212) and one Gram-(−) strain (Escherichia coli (E. coli) ATCC 25922). The 2-salicyloylbenzofuran heterocycles were generated by Rap–Stoermer condensation of salicylaldehydes with phenacyl bromides and then converted to diverse O-ether derivatives by Williamson synthesis. The targeted products were screened for in vitro qualitative (zone of inhibition) and quantitative (MIC) antibacterial activities by agar well diffusion assay and agar dilution method. Amongst the compounds, those bearing carboxylic acid functional group were found to exhibit reasonable activity against Gram-(+) bacterial strains including S. faecalis, MSSA and MRSA with the most potent antibacterial agent 8h (MICs = 0.06–0.12 mM). Besides, the 2-salicyloylbenzofurans partly displayed inhibitory activity against MRSA with the best MICs = 0.14 mM (8f) and 0.12 mM (8h). Finally, the antibacterial results preliminarily suggested that the substituent bearing carboxylic acid group at salicyloyl-C2 and the bromine atoms on the benzofuran moiety seem to be the functionality necessary for antibacterial activities.

Energetic Effect of the Carboxylic Acid Functional Group in Indole Derivatives.

The standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, yielding -(222.2 ± 3.5) kJ·mol-1 and -(234.1 ± 2.1) kJ·mol-1 for indole-3-carboxylic acid and 1-methylindole-3-carboxylic acid, respectively. Computational studies, at the G3(MP2) composite level, were conducted for indole-3-carboxylic acid and 1-methylindole-3-carboxylic acid as a complement of the experimental work, and they were also extended to the remaining isomers, indole-2-carboxylic acid, 1-methylindole-2-carboxylic acid, 3-methylindole-2-carboxylic acid, and 2-methylindole-3-carboxylic acid, to provide reliable estimates of the corresponding thermochemical parameters. The agreement of the estimates of the standard gas-phase enthalpy of formation so obtained, indole-2-carboxylic acid -(223.6 ± 0.8) kJ·mol-1, 1-methylindole-2-carboxylic acid -(223.7 ± 0.8) kJ·mol-1, 3-methylindole-2-carboxylic acid -(251.6 ± 1.0) kJ·mol-1, indole-3-carboxylic acid -(227.1 ± 1.1) kJ·mol-1, 1-methylindole-3-carboxylic acid -(238.0 ± 1.0) kJ·mol-1, and 2-methylindole-3-carboxylic acid -(267.2 ± 1.0) kJ·mol-1, with the available experimental data gives us additional confidence for the situations not studied experimentally. The enthalpic effect resulting from the entrance of the carboxyl group into the indole ring was discussed, and an enthalpic stabilization was found for indole and pyrrole derivatives when compared with other similar systems.

Cinnamic Acid Derivatives as α-Glucosidase Inhibitor Agents

This paper reviews biological activity of some cinnamic acid derivative compounds which are isolated from natural materials and synthesized from the chemical compounds as an agent of α-glucosidase inhibitors for the antidiabetic drug. Aegeline, anhydroaegeline and aeglinoside B are natural products isolated compounds that have potential as an α-glucosidase inhibitor. Meanwhile, α-glucosidase inhibitor class of derivatives of cinnamic acid synthesized compounds are p-methoxy cinnamic acid and p-methoxyethyl cinnamate. Chemically, cinnamic acid has three main functional groups: first is the substitution of the phenyl group, second is the additive reaction into the α-β unsaturated, and third is the chemical reaction with carboxylic acid functional groups. The synthesis and modification of the structure of cinnamic acid are very influential in inhibitory activity against α-glucosidase.

Poly(perylene‐alt‐phenyleneethynylene)s with multiple pendant ester groups in various lengths: Synthesis, photophysics and selective hydrolysis

ABSTRACTFive fluorescence polymers with poly(perylene‐alt‐phenyleneethynylene)s (PPPEs) backbone and multiple side chains containing ester‐groups were synthesized via Sonogashira coupling reaction. These polymers were soluble in common organic solvents to form red‐orange solution. The polymer powders had dark red color. The absorption/emission spectra of these polymers were similar, with absorption bands between 300 and 600 nm and an emission peak between 520 and 700 nm. Furthermore, the ester groups of the side chains were partially or completely hydrolyzed, resulting in the fluorescence PPPEs with tunable density of carboxylic acid functional groups on the polymer chains as interaction/reaction sites for further applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1880–1886

Fully bio-based aliphatic thermoset polyesters via self-catalyzed self-condensation of multifunctional epoxy monomers directly extracted from natural sources

The use of bio-based raw material is regarded as a sustainable way to address environmental concerns. A naturally occurring monomer, 9,10-epoxy-18-hydroxyoctadecanoic acid (EFA), was retrieved from outer birch bark. A series of model experiments revealing relative reaction rates for epoxide, carboxylic acid, and alcohol functional groups was investigated. Real-time Fourier transform infrared spectroscopy and nuclear magnetic resonance were used to follow the different model experiments. The results on the model systems were then compared to the thermoset formation of thermally cured EFA. Finally, the adhesive properties of crosslinked EFA on different substrates were evaluated.

Stability of Trithiocarbonate RAFT Agents Containing Both a Cyano and a Carboxylic Acid Functional Group.

The hydrolytic degradation of widely used cyano-containing, acid-bearing trithiocarbonate reversible addition-fragmentation chain-transfer (RAFT) agents has been identified and shown to effect the RAFT polymerization and end-group fidelity of PMMA polymers. The hydrolysis occurred when the RAFT agents were stored under the recommended conditions. Degradation was identified in both commercially available and popular synthetic RAFT agents. 1H and 13C NMR as well as mass spectroscopy show that the cyano functionality hydrolyzes to the amide adduct. Doping of this amide degradation product into RAFT polymerizations of MMA results in increased dispersities and changes in expected end-group fidelities. The ability to identify this degradation product and remove it from the RAFT agent before use will allow better control over polymer properties and postmodification processes commonly used in complex polymer systems, nanomedicines, and bioconjugates.

Nonconventional trans‐Platinum Complexes Functionalized with RDG Peptides: Chemical and Cytototoxicity Studies

In order for platinum complexes to target cancer cells, trans‐PtII or trans‐PtIV complexes were bioconjugated to the cyclic peptide cRGDfK (cRGD), which has an affinity for αvβ3‐integrin receptors, through its 4‐picolinic acid spectator ligands. To tackle this goal, the PtII and PtIV precursors were activated at their carboxylic acid functional group, and futher treated with the cRGDfK peptide, to afford the bioconjugates PtII–cRGD and PtIV–cRGD, respectively. PtII–cRGD was studied by 195Pt NMR spectroscopy, which confirmed the presence of the PtII center. In contrast, the characterization of PtIV–cRGD was not possible, due to the tendency of this complex to undergo reduction to PtII in solution. Thus, only the PtII–cRGD complex was used for further biological studies, and it exhibited some cytotoxic activity against the HUVEC (human umbilical vein endothelial cells) cell line, which has the highest levels of αvβ3 expression. However, no improved effects were observed with respect to the PtII–pic precursor. Studies by ICP‐MS showed enhanced intracellular accumulation for PtII–cRGD, with respect to PtII–pic in cancer cells. Overall, these results show that, while PtII bioconjugation enhances the uptake of the compound, it did not translate into increased cytotoxicity.

The Immobilization of Fructose Dehydrogenase on Nanoporous Gold Electrodes for the Detection of Fructose

AbstractNanoporous gold electrodes were utilized as a support for the detection of d‐fructose. The immobilization of fructose dehydrogenase was achieved by adsorption on thiol‐ and diazonium‐bound carboxylic acid functional groups and subsequent crosslinking through cabodiimide‐initiated amide bond formation. The biosensor showed a linear response in the range 0.05–0.3 mM of d‐fructose with a sensitivity of 3.7±0.2 μA cm−2 mM−1 and a limit of detection of 1.2 μM. The response of the biosensor in a range of natural sweeteners and beverages compared very favorably to the results obtained by a commercially available kit. Accurate readings were obtainable after a very fast response time of less than 5 seconds. The biosensor showed high specificity towards d‐fructose in the presence of interfering sugars.

A reinvestigation of a colorimetric method aimed at quantifying minute amounts of carboxylic acids present in polystyrene and poly(n‐alkyl methacrylate)s

ABSTRACTA reinvestigation of a method (Christoff, M.; Yamaki, S. B.; de Oliveira, M. G.; Atvars, T. D. Z. J. Appl. Polym. Sci. 2004, 92, 830–838) aimed at quantitatively determining trace amounts of residual carboxylic acid functional groups in polymethacrylates and polystyrene has been carried out. The original technique was based on the monitoring of an absorption band in the UV–visible region (610 nm) that appears after known amounts of polymer are added to a benzene solution containing the basic form of the Nile Blue A dye. It is shown here that the assumption upon which the methodology is based, that is, the occurrence of a 1:1 stoichiometric and complete proton transfer of the carboxylic acid to the dye, is invalid and yields greatly underestimated values for the COOH contents, possibly by 2–3 orders of magnitude. In addition, temperature strongly influences the equilibrium constant for the acid‐base reaction. Lastly, preparation and storage of the analytical solution was found to be problematic, supporting earlier claims that hydrolysis of Nile Blue A base does occur when preparing the benzene solution and/or over storage, yielding Nile Red dye whose absorption in the visible part of the spectrum significantly overlaps. Based on the above results, further use of this technique, at least in its quantitative version, should be discouraged. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44931.

Hydrogen bond-directed assembly of silsesquioxanes cubes: synthesis of carboxylic acid POSS derivatives and the solid state structure of octa[2-(p-carboxyphenyl)ethyl] silsesquioxane

The octa[2-(p-carboxyphenyl)ethyl] and octa[2-(4-carboxy-1,1′-biphenyl)ethyl] silsesquioxane were synthesised under mild reaction conditions upon hydrogenolysis of the corresponding benzyl-ester derivatives. The octa[2-(p-carboxyphenyl)ethyl] silsesquioxane was shown to self-assemble upon formation of carboxylic acid dimers. The presence of eight carboxylic acid functional groups allowed to obtain an ordered silsesquioxane hybrid network. The X-ray crystal structures of the octa-ester and of the octa-acid were determined. The three-dimensional conformation of the ester provided an interpenetrated compact packing of the molecular building blocks without any specific supramolecular interaction. The two-dimensional character of the acid and the directionality of the hydrogen bond pattern of a dimer of acid led to the formation of hydrogen-bonded ribbons. It showed that functionalized silsesquioxane precursors capable of hydrogen bonding are of interest to generate nanostructured materials through self-organization processes. Moreover, the use of carboxylic acid groups is interesting not only because of their ability to form carboxyl dimer structures by hydrogen bonding but also because of their ability to form metal carboxylate derivatives that may lead to new organised hybrid metal organic silica frameworks.

A Comparative Anaylsis of Aspirin from Various Analgesic Formulations Using Titrimetry, Spectroscopic and Hypenated Chromatographic Techniques

Aspirin, acetyl salicylic acid or 2-acetoxybenzoic acid, has the carboxylic acid functional group hence easier to quantify using a strong alkali like NaOH. In most analgesic drug formulations in tablets form, aspirin is generally bind or compounded with other excipients or substituents which are acidic in nature and has acidic groups thus reacts easily with NaOH, hence making sodium hydroxide not a suitable reagent for quantifying aspirin in multicomponent aspirin tablet formulation. Six different tablets from reputable drug manufacturing company containing aspirin as an active substance were taken. Methods using sodium hydroxide as the main reagent in quantification involves a lot of stoichiometric mathematical manipulations as in case of titrimetric method while UV-VIS spectroscopy via multivariate calibration gave values at lower limit or outside the lower limits of US & BP pharmacopeia with respect to label claims, while the hyphenated chromatographic techniques such as, GC-MS and HPLC gave a very good resolution and very precise results within the pharmacopeia limits.

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

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

Preparation, characterization and drug delivery study of a novel nanobiopolymeric multidrug delivery system

New nanocarrier for codelivery of curcumin and doxorubicin as the anticancer drugs was synthesized using biocompatible and biodegradable materials. Firstly, an inclusion complex of amylose (Am) and curcumin (CUR) was formed through entrapment of curcumin into the amylose helices. Then the surface of amylose-curcumin (Am-CUR) complex was modified by polycaprolactone (PCL) via esterification reaction between hydroxyl functional groups of amylose and carbonyl groups of PCL. Finally, poly citric acid (PCA) reacted with terminal hydroxyl groups of PCL by esterification reaction. Then, doxorubicin (DOX) reacted with the surface carboxylic acid functional groups of Am-CUR-PCL-PCA through noncovalent interactions to form Am-CUR-PCL-PCA-DOX as a multidrug delivery system. These new synthesized nanomaterials were characterized by spectroscopic measurement methods such as IR spectroscopy, UV–vis spectroscopy, NMR spectroscopy, and scanning electron microscopy. FE-SEM analyses and DLS measurements showed that the hydrodynamic dimensions of Am-Cur-PCL-PCA were about 50nm. Due to the presence of ester bonds, the synthesized nanomaterials are pH sensitive. Furthermore, the resulting copolymer was completely water soluble because of the hydrophilic nature of poly citric acid part of copolymer and therefore successfully can be utilized in biomedical applications.

Systematic investigation of the excited-state properties of anthracene-dicarboxylic acids

Abstract We report the photophysical properties of three anthracene-dicarboxylic acids – 1,4-anthracene dicarboxylic acid (1,4-ADCA), 2,6-anthracene dicarboxylic acid (2,6-ADCA) and 9,10-anthracene dicarboxylic acid (9,10-ADCA) – in a series of polar aprotic solvents using steady-state absorption spectroscopy, steady-state emission spectroscopy and time-correlated single photon counting emission lifetime spectroscopy. The addition of carboxylic acid functional groups on the anthracene ring perturbs the electronic transitions oriented along the longitudinal and transverse axes to varying degrees, resulting in differences in the photophysical properties. The three anthracene derivatives exhibit very different excited-state properties in basic solution compared to acidic and neutral solutions. Density functional theory (DFT) calculations reveal that the lowest-energy ground-state structures of both 2,6-ADCA and 1,4-ADCA have dihedral angles between the carboxylic acids and aromatic planes of θ = 0°. For 9,10-ADCA, the same dihedral angle increases to θ = 56.6°. Time-dependent DFT calculations suggest that the carboxyl groups of 1,4-ADCA and 2,6-ADCA remain coplanar with the anthracene ring system in the excited state. In contrast, the calculations reveal significant changes between the ground and excited geometries for 9,10-ADCA as the dihedrals decrease from 56.6° to 27.7° in the first excited state, and puckering of the anthracene moiety of 9,10-ADCA is observed.

Synthesis of Carboxylic Functionalized Multi Wall Carbon Nanotubes and Their Application for Static Charge Dissipative Fibers

In the present study, multi wall carbon nanotubes (CNTs) were chemically functionalized by concentrated nitric acid refluxing for 8 hours to form acid functionalized CNTs (FCNTs). Fourier transformed infrared spectra reveal the formation of carboxylic acid (-COOH) functional groups on the surface of chemically treated CNTs.