Presence Of Picolinic Acid Research Articles

Iron‐Catalyzed Epoxidation of Linear α‐Olefins with Hydrogen Peroxide

AbstractThe combination of Fe(OTf)2 with N‐methyl bis(picolylamine) (Me‐bpa) L7 enables epoxidation of linear olefins including terminal, internal, and cyclic ones, using hydrogen peroxide as terminal oxidant under mild conditions. In the presence of picolinic acid as additive improved yields of epoxides up to 75 % have been achieved.

Delineating the influence of picolinic acid on Eu(iii) sorption by γ-alumina.

The present study aims at understanding the sorption mechanism of Eu(iii) by γ-alumina in the presence of picolinic acid (PA), a decontaminating agent used in the nuclear industry, through batch sorption studies, spectroscopy and surface complexation modeling. PA is weakly sorbed by γ-alumina, with the sorption increasing with pH up to 4.5 and decreasing with further increase in pH. Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) measurements indicate that PA forms an inner sphere surface complex on γ-alumina. The presence of PA does not affect Eu(iii) sorption by γ-alumina at low [Eu(iii)], while it drastically reduces Eu(iii) sorption at high [Eu(iii)]. Similar Eu(iii) sorption profiles with different addition sequences of Eu(iii) and PA suggest identical Eu(iii) surface species for Eu(iii) sorption on γ-alumina in the presence of PA which has been validated by time resolved fluorescence spectroscopy (TRFS). TRFS measurements of Eu(iii) sorbed on γ-alumina in the absence (binary systems) and presence of PA (ternary systems) exhibited two components 1 & 2. The lifetime value of component 1 in ternary systems is enhanced compared to that in binary systems signifying the formation of new surface species containing Eu(iii), PA and the γ-alumina surface whereas the similarity of component 2 in both the binary and ternary systems reveals an almost identical coordination environment of Eu(iii) in the two types of system. Using the spectroscopic information obtained from TRFS, Eu(iii) sorption, at high [Eu(iii)], in ternary systems has been successfully modeled by considering Eu(iii) bridged PA surface species at both low and high affinity sites of γ-alumina. At low [Eu(iii)] both PA and Eu(iii) bridged ternary surface complexes only at high affinity sites of γ-alumina could describe the Eu(iii) sorption adequately.

Kinetic study for the oxidation of dl-mandelic acid by tripropylammonium fluorochromate in the absence and presence of picolinic acid and 1,10-phenanthroline

Kinetic study for the oxidation of dl-mandelic acid by tripropylammonium fluorochromate in the absence and presence of picolinic acid and 1,10-phenanthroline

An electrochemical study on interaction of copper ions with three isomers, picolinic, nicotinic and isonicotinic acids at physiological pH

The electrochemical behaviors of copper ions complexed with picolinic, nicotinic and isonicotinic acids (2-, 3- and 4-pyridinecarboxylic acids) in Britton–Robinson buffer (pH 7.4) was studied by polarographic and voltammetric techniques on a mercury electrode. This study showed that the reduction of complexed copper ions in the presence of nicotinic acid (NA) was carried out in two one-electron steps [Cu(II)/Cu(I) and Cu(I)/Cu(0)] whereas this cathodic process in the presence of picolinic acid (PA) or isonicotinic acid (INA) occurred in one two-electron step [Cu(II)/Cu(0)]. The stability of the Cu(I) complex can be sourced from the positions of carboxylate substituents on these isomeric ligands, binding to the copper center.

Monitoring of Silver Electrodeposition onto HOPG Electrodes in the Presence of Picolinic Acid by in Situ Surface-Enhanced Raman Spectra Measurements

In situ surface-enhanced Raman spectra (SERS) have been recorded during silver potentiodynamic electrodeposition onto HOPG electrodes from solutions containing silver perchlorate and picolinic acid (PA). Modification of the composition and pH of the electrolyte has allowed us to achieve an adequate control of the electroactive species distribution in solution. The adsorption behavior of different PA species on silver growing crystallites has been studied by using the potential dependence of SERS signals. Analysis of the vibrational bands from additive molecules has allowed us to establish that at pH > 3.0 the PA anion is the most stable species on the electrode surface, whereas the predominant species in solution is the zwitterion. At pH 0.3, adsorption of zwitterion and anion species onto the silver surface, even though the PA cation is predominant in the solution, has been evidenced. For all the SERS spectra it was possible to infer the adsorption geometry and the ClO4– ion coadsorption. Detection of in...

Electrodeposition of copper on glassy carbon electrodes in the presence of picolinic acid

The electrodeposition of copper on glassy carbon electrodes in the presence of picolinic acid (PA) was investigated by means of voltammetric, chronoamperometric and electrochemical impedance spectroscopy measurements complemented by UV–vis spectroscopy and SEM imaging. Voltammetry shows the appearance of two cathodic current peaks that are assigned to the electroreduction of copper ions and [Cu(PA) 2 ] 2+ soluble complex species. The anodic stripping of the metallic layer shows two electrochemical processes related to the formation of cupric ions that are produced from the electro-oxidation of both the deposited copper layer and the cuprous species that result from the chemical reaction between the metallic layer and cupric ions at the interface. This second contribution appears to be influenced by the initial conditions of the electrode surface and the presence of PA in solution. Voltammetry and potentiostatic current transients show that copper deposition occurs though a nucleation and growth process. From the analysis of the transients an instantaneous nucleation with 3D growth process under diffusion control is concluded, although a deviation in the curves from the model is observed. This deviation from the model, usually found in other systems, is explained in terms of the morphological characteristics of the particles depositing on the electrode surface. SEM images show the formation of nuclei on the glassy carbon surface and a change in the morphological characteristics of the deposit when the reaction occurs in the presence of PA. The Nyquist plots show a single capacitive constant at high frequencies, related to the charge transfer of copper ions, and a Warburg-type contribution at low frequencies, related to the diffusion of copper ions from the solution to the electrode surface. Values of the charge transfer resistance result lower in the presence of PA. The corresponding Bode plots show a good agreement between experimental and fitted data.

Nucleation and growth of silver nanostructures onto HOPG electrodes in the presence of picolinic acid

Fil: Vazquez, Cecilia Irene. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones en Fisico-quimica de Cordoba. Universidad Nacional de Cordoba. Facultad de Ciencias Quimicas. Instituto de Investigaciones en Fisico-quimica de Cordoba; Argentina

Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid**Project supported by the Center for Advanced Materials Processing (CAMP) at Clarkson University, the National Integrate Circuit Research Program of China (Grant No. 2009ZX02023-3), the National Basic Research Program of China (GrantNos. 2007CB935400, 2010CB934300 and 2006CB302700), the National High Technology Development Program of China

We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid. The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing. By using zeta potential analyzer, particle size analyzer, horizon profilometer, thermogravimetric analysis and Fourier transform infrared spectroscopy, the pre- and the post-polished wafer surfaces as well as the pre- and the post-used ceria-based slurries are compared. Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed.

C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion

Abstract C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion has been established performing the reaction of 1,2-bis(2-pyridylmethylthio)ethane(BPT1), 1,3-bis(2-pyridyl-methylthio)propane(BPT2) and 3,4-bis(2-pyridylmethylthio)-5-methyltoluene (BPT3) with Bu4N[ReOCl4] in dry alcoholoic medium. In case of BPT1 and BPT2, new 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3-(2-pyridylmethylthio)propane-1-thiol (L2H) ligand, respectively were formed in situ through cleavage of one C–S(thioether) bond, resulting in the neutral oxorhenium(V) complexes of formulation [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b); where as in case of BPT3, binary oxorhenium(V) complex of 3,4-dimercapto-toluene ligand (L3H2), formulated as Bu4N[ReO(L3)2] (1c) through cleavage of two C–S(thioether) bonds. The presence of picolinic acid, as by-product in the filtrates of the C–S bond cleavage reactions in dry alcohol, was detected by treatment of copper(II) salts and GC–MS techniques. But in hydrated alcoholic medium no C–S bond cleavage induced by ReO(V) ion occurred in any of the BPT systems rather the conversion of ReO(V) into perrhenate salt was observed; this reaction mixture, in turn on reaction with copper(II) nitrate trihydrate salt, produce [Cu(BPT)Cl]ReO4 (2) type complexes. The solid-state structures of complexes 1a and 2a were established by X-ray crystallography.

Attaining Control by Design over the Hydrolytic Stability of Fe-TAML Oxidation Catalysts

The iron(III) complexes of tetra amidato macrocyclic ligands (TAMLs) ([Fe{1-X1-2-X2C6H2-4,5-(NCOCMe2NCO)2CR2}(OH2)]- , 1: X1 = X2 = H, R2 = Me2 (a), R2 = (CH2)2 (b); X1 = X2 = Cl, R2 = F2 (c), etc.), which the proton is known to demetalate at pH < 3, are also subject to catalyzed demetalation by Brønsted acid buffer components at pH 4-9 such as H2PO4-, HSO3-, and CH3CO2H, HO2CCH2CO2-. Buffers based on pyridine (py) and tris(hydroxymethyl)aminomethane (TRIS) are catalytically inactive. Where reactions proceed, the products are demetalated TAMLs and iron species of variable composition. Pseudo-first-order rate constants for the demetalation (kobs) are linear functions of the acid concentrations, and the effective second-order rate constants k1,eff have a hyperbolic dependence on [H+] (k1,eff = a1[H+]/(b1+[H+]). The rate of demetalation of 1a in H2PO4-/HPO42- buffer is appreciable, but the kobs values for 1b and 1c are immeasurably low, showing that the rates are strongly affected by the CR2 or "tail" fragments, which are known to potently affect the TAML basicity. The reactivities of 1 depend insignificantly on the aromatic ring or "head" group of 1. The proposed mechanism involves precoordination of the acidic buffer species followed by hydrolysis. The demetalating abilities of buffer species depend on their structures and acidities. Thus, although pyridine-2-carboxylic (picolinic) acid catalyzes the demetalation, its 3- and 4-isomers (nicotinic and isonicotininc acids) are inactive. The difference is rationalized to result from the ability that only coordinated picolinic acid has to deliver a proton to an amidato nitrogen in an intramolecular manner. The reaction order in picolinic acid equals one for 1a and two for 1b. For 1b, "inactive" pyridine and nicotinic acid speed up the demetalation in the presence of picolinic acid, suggesting that the second order arises from the axial binding of two pyridine molecules, one of which must be picolinic acid. The binding of pyridine- and imidazole-type ligands was confirmed by UV/vis equilibrium measurements and X-ray crystallography. The implications of these mechanistic findings for designing superior Fe-TAML oxidation catalysts and catalyst formulations are discussed using the results of DFT calculations.

Mechanism of copper electrodeposition in the presence of picolinic acid

The influence of picolinic acid (PA) on copper deposition from a slightly acidic sodium sulphate electrolyte has been studied over a wide range of concentration and pH by cyclic voltammetry. The mechanism by which the copper electrodeposition process in the presence of PA takes place, depends on the chemistry and electrochemistry characteristics of the additive. Depending on the PA concentration and pH of the solution, five different cathodic current peaks are obtained, which are assigned to different steps involving copper deposition from free-Cu 2+ ions and [Cu(PA) n ] 2+ complex species as well as H + ions electroeduction. Fine-grained, highly adherent and bright copper deposits were obtained.

Micellar Effect on the Reaction of Chromium(VI) Oxidation of L‐Sorbose in the Presence and Absence of Picolinic Acid in Aqueous Acid Media: A Kinetic Study

AbstractThe kinetics and mechanism of chromic acid oxidation of L‐sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L‐sorbose]T » [PA]T » [Cr(VI)]T, at different temperatures. In the absence of PA, the monomeric chromic acid undergoes esterification with the substrate followed by the acid catalysed redox decomposition of the Cr(VI)‐substrate ester through glycol splitting to formaldehyde and the lactone of C5‐aldonic acid and Cr(IV) which subsequently participates in the faster reactions. In the presence of PA, the Cr(VI)‐PA complex produced in a pre‐equilibrium step experiences a nucleophilic attack by the substrate to produce a ternary complex which decomposes through glycol splitting giving rise to the organic products and Cr(IV)‐PA complex. Both the uncatalysed and PA‐catalysed paths show the first‐order dependence on [L‐sorbose]T and [Cr(VI)]T. The PA‐catalysed path is first‐order in [PA]T and it shows a fractional order in [H+]. The uncatalysed path shows a second‐order dependence on [H+]. In the presence of the surfactants like N‐cetylpyridinium chloride (CPC, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic sulfate), the reaction orders remain unchanged. CPC has been found to inhibit both the uncatalysed and PA‐catalysed paths while SDS shows the rate accelerating effect for both the uncatalysed and PA‐catalysed paths. The observed micellar effects have been rationalised by considering the distribution of the reactants between the micellar and aqueous phases in terms of the proposed reaction mechanism.

Minimization of Cu and Ni interferences in the determination of Sb by hydride generation atomic absorption spectrometry: the use of picolinic acid as masking agent and the influence of l-cysteine

The minimization of copper and nickel interference on the determination of antimony by hydride generation atomic absorption spectrometry using picolinic acid and l-cysteine as masking agents was studied. Concentrations up to 4000 and 1000 mg l −1 of nickel and copper respectively were found to be tolerable in the presence of picolinic acid. The simultaneous presence of both transition metals could be tolerated by using a mixture of picolinic acid and l-cysteine. In the analysis of a nickel oxide certified reference material good agreement between the recommended and found values was verified. A detection limit (3 s, n=10) of 0.1 μg Sb g −1 in the original sample was estimated.

Drug Targeting to the Brain: Transfer of Picolinic Acid Along the Olfactory Pathways

Picolinic acid (PA) protects against quinolinic acid- and kainic acid-induced neurotoxicity in the brain. To study the uptake of PA to the brain, we administered [3 H]PA via a unilateral nasal instillation or iv injection to mice. Autoradiography demonstrated a rapid uptake of radioactivity in the olfactory nerve layer and in the ipsilateral olfactory bulb (OB) following nasal instillation of [3 H]PA. After 4 h, there was a high level of radioactivity in the central parts of the ipsilateral OB and olfactory peduncle. Moreover, iv injection of [3 H]PA demonstrated a selective uptake and retention of radioactivity in the OB. Gas chromatography-mass spectrometry (GC-MS) demonstrated the presence of PA and PA-glycine conjugate in the OB. In mice with reduced peripheral olfactory innervations there was a decreased uptake of [3 H]PA in the OB as compared to controls suggesting that an intact olfactory neuroepithelium is a prerequisite for an uptake of PA to the OB. There is an increased interest in brain targeting of drugs with limited ability to pass the blood-brain barrier. The present results demonstrate that PA fulfils structural requirements for a transfer along the olfactory pathways to the brain.

Electrodialysis of Vanadium(III) and Iron(II) Ions from a Simulated Decontamination Solution

The transport of vanadium(III) and iron(II) ions through the Nafion 117 cation-exchange membrane in the presence of picolinic acid was investigated by simulating the equilibrium distribution of ionic species as a function of pH, and by electrodialyzing the simulated waste solution. From distribution calculations of the model reaction systems it could be predicted that at pH 1.6 most vanadium ions exist predominantly in the form of the VIII(Pic−)2 + complex, and this form of complex permeates across the cation-exchange membrane during electrodialysis. The experimental results, including variations in the color and cation concentrations of the catholyte, confirm the existence of the vanadium(III) picolinate complex. Iron ions permeated into the catholyte were converted to their hydroxide precipitates, which could be formed at the high pH condition resulting from the reduction of hydrogen ions and the production of OH− ions by water electrolysis at the cathode. It was also found that the in-situ precipitation of iron in the electrodialyzer could be self-modulated by shifting the catholyte pH from the acidic state to the alkaline state during electrodialysis operation.

Kinetics and Mechanism of the Chromium(VI) Oxidation of Formic Acid in the Presence of Picolinic Acid and in the Presence and Absence of Surfactants

The kinetics and mechanism of picolinic acid (PA)- catalysed oxidation of formic acid have been studied in aqueous HClO4 media under the experimental conditions, 103[Cr(VI)]T = 0.67-2.67 mol dm-3, [PA]T = 0.01-0.12 mol dm-3, [HCO2H]T = 0.1-0.8 mol dm-3, [H+] = 0.35-1.5 mol dm-3,1 = 1.5 mol dm-3 in the temperature range 25-40° C. The kinetic parameters of the catalysed path have been compared with those of the relatively slower uncatalysed path which proceed parallelly with the catalysed path. In the catalysed path, Cr(VI)-PA cyclic complex formed at the pre-equilibrium step receives a nucleophilic attack at the Cr(VI) centre by the substrate leading to a ternary complex with the release of a proton in a reversible path. Then the ternary complex experiences the redox decomposition at the rate-determining step giving rise to Cr(IV)-PA complex and CO2. Then the Cr(IV)-PA complex reacts faster ultimately giving rise to Cr(III)-PA complex. The anionic surfactant sodium dodecyl sulfate (SDS) catalyses both the uncatalysed and catalysed paths in aqueous HClO4 media while the cationic surfactant cetyl pyridinium chloride (CPC) inhibits the reactions in aqueous H2SO4 media. In the presence of the surfactants, applicability of the Piszkiewicz model has been tested for the ΡΑ-catalysed path. Micellar effects are in conformity with the proposed mechanism.

The selective functionalization of saturated hydrocarbons. Part 47. Investigation of the size of the reagent involved in the Fe II–Fe IV manifold

Competition experiments between cyclohexane and various aromatic substrates have been carried out in pyridine-acetonitrile in order to ascertain the steric requirements of the Fe II-H 2O 2 reagent in comparison with the Fe III-H 2O 2 reagent already studied. The latter is distinctly larger and much less reactive than the former. Although these results might indicate that the Fe II-H 2O 2 reagent is simply the hydroxyl radical, the chemistry observed is strictly dependent on the presence of picolinic acid. Without the latter, no significant oxidation of any substrate is observed. Hydroxyl radical formation (Fenton Chemistry) is not considered to be ligand dependent in preceding investigations.

Characteristic of the Ag(II)/Ag(I) system in the presence of picolinic acid in water

Using IR spectrophotometry, potentiometry, and quantitative analysis, it was ascertained that the process of complexing Ag(I) ions with picolinic acid (Hpic) results in the formation of complexes such as AgH(pic)2 (pH<4) and Ag(pic)2− (pH≌7). Complex Ag(II) occurs in the form Ag(pic)2o independently of the medium. The values of conditional complex stability constants (μ=0.1) for Ag(pic)o and Ag(pic)2− found by potentiometry are as follows: β01=3.4×103 and β02=1.2×106. Redox systems formed in solutions were described and their formal potentials were determined by chronovoltamperometry: $$\begin{gathered} Ag(pic)_{2 }^o + e \rightleftarrows Ag (pic)_2^ - {\rm E}_f^o = 1.388 V vs. NHE \hfill \\ Ag(pic)_{2 }^o + e \rightleftarrows Ag (pic)^o + pic^ - {\rm E}_f^o = 1.240 V vs. NHE. \hfill \\ \end{gathered} $$

Sorption of magnesium–picolinate complexes on a macroporous styrene–divinylbenzene copolymer containing immobilized 8-hydroxyquinoline and on the copolymer itself

The sorbent XAD-OXINE was prepared by covalently binding 8-hydroxyquinoline onto the surface of the macroporous copolymer Amberlite XAD-2 to give about 20% surface coverage. Sorption, onto both XAD-2 and XAD-OXINE, of the magnesium-containing species that are present in solutions of magnesium ion and picolinic acid was studied by the column equilibration/atomic absorption technique at solution pH of 6.00 and 7.50 and ionic strength of 0.25. By using solutions containing various amounts of added magnesium and picolinic acid, in which the ratio of the two metal–ligand complex species, MgP+/MgP2, varied greatly (P− is the ligand picolinate), it was shown that neither the species Mg2+ nor the species MgP+ sorb to an appreciable extent onto the parent polymer XAD-2, but the neutral species MgP2 sorbs strongly and exhibits a linear isotherm. Then, by measuring the sorption isotherm of the species Mg2+ on XAD-OXINE in the absence of picolinic acid, by measuring the overall sorption of magnesium-containing species on XAD-OXINE in the presence of picolinic acid, and by assuming that the sorption of the species MgP2 onto XAD-OXINE was about the same as it was on XAD-2, it was possible to show that the species MgP+ sorbs strongly onto XAD-OXINE, and exhibits linear sorption isotherms. Thus, XAD-OXINE sorbs all three species Mg2+, MgP+, and MgP2. Keywords: Amberlite XAD-2, immobilized oxine, magnesium ion.

Characterization and Quantitation of a Zinc-Binding Ligand in Human Milk

Summary: A low-molecular-weight zinc-binding ligand from human milk has been isolated and characterized. The ligand was isolated by chromatography on Dowex 50, Dowex 1, and Sephadex G-15 equilibrated with 0.153 mM Zn(NO3)2. Mass spectroscopy, thin-layer chromatography, and infrared spectroscopy proved that the zinc-binding ligand isolated by this method from human milk is pyridine-2-carboxylic acid, commonly known as picolinic acid. The concentration of picolinic acid in human milk was 308 μM, the concentration in one brand of processed cow's milk was 20 μM, but picolinic acid was undetectable in a second brand of cow's milk and in four different infant formulas. Weanling rats fed supplemental picolinic acid absorbed significantly more dietary zinc and gained significantly more weight than rats fed an unsupplemented diet. The results suggest that the high bioavailability of zinc in human milk results from the presence of picolinic acid, a bidentate chelating ligand which facilitates zinc absorption from the intestine. Speculation: The high bioavailability of zinc in human milk results from the presence of picolinic acid, a bidentate chelating ligand which facilitates zinc absorption from the intestine.