Pyridine In Aqueous Solution Research Articles

Probing the Fermi resonance of pyridine surrounded by hydrogen bonding network by density functional theory

The Fermi resonance (FR) occurs between the ring breathing vibrational (ν1) and the triangular stretching (ν12) mode of pyridine in aqueous pyridine solution was studied using Raman spectroscopy combined with density functional theory (DFT) calculations. The effect of H-Bond on the FR in the mixture was performed by MD analysis. Combined with the FR parameters, it was found that due to the H-Bond effect the FR coupling changed significantly when the pyridine mole fractions were near 0.7 and 0.5, respectively. The water H-Bond network structure is most favorable for pyridine molecule bonding at a pyridine mole concentration around 0.5, and water preferentially affinity to the pyridine molecule at x = 0.7. In addition, we analyzed the OH vibrational region at different mole fractions and theoretically calculated Py associated OH in specific molecular bonds.

Ultra-sensitive detection of pyridine in water using zinc porphyrin incorporated in a transparent hydrophobic film

In this study, we investigated the axial coordination reaction between pyridine and zinc meso-tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) incorporated in a transparent layered double hydroxide (LDH) film modified with 1-decanesulfonate (C10S) in an aqueous solution. The apparent equilibrium constant ({K}_{11}) of the axial coordination reaction between pyridine and ZnTPPS incorporated in the transparent ZnTPPS/C10S/LDH film was approximately 260 times that of the corresponding reaction in an aqueous solution. The hydrophobisation of the LDH interlayer space by C10S, which led to the elimination of water molecules surrounding ZnTPPS and enabled the accumulation of pyridine molecules, was responsible for such a significant increase in the apparent {K}_{11} value. The developed film can detect pyridine in aqueous solutions with ultra-high sensitivity in the order of 10−5 mol/L through changes in the colour tone, which is comparable to the molecular detection ability of insect antennae. The sensing response was also observed at pyridine concentrations as low as 10−9 mol/L.

Soft X-ray Absorption Spectroscopy of Liquids for Understanding Chemical Processes in Solution.

Soft X-ray absorption spectroscopy (XAS) involving excitation processes of a core electron to unoccupied states is an effective method to study local structures around excited C, N, and O atoms in liquid samples. Since soft X-rays are strongly absorbed by air and liquid itself, we have developed transmission-type liquid flow cells, where the absorbance of liquid samples can be easily reduced and optimized by controlling the liquid thickness. By using the transmission-mode XAS techniques, we have investigated local structures of several liquid samples such as concentration dependence of aqueous pyridine solutions and unexpected temperature-dependent structural changes in liquid benzene from the precise energy shift measurements in XAS spectra with the help of molecular dynamics simulation and inner-shell calculations. These XAS techniques are also applied to in situ/operando observation of chemical processes in solutions such as catalytic and electrochemical reactions.

Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes.

The fully polarizable Quantum Mechanics/Molecular Mechanics (QM/MM) approach based on fluctuating charges and fluctuating dipoles, named QM/FQFμ [T. Giovannini et al., J. Chem. Theory Comput. 15, 2233 (2019)], is extended to the calculation of vertical excitation energies of solvated molecular systems. Excitation energies are defined within two different solvation regimes, i.e., linear response (LR), where the response of the MM portion is adjusted to the QM transition density, and corrected-Linear Response (cLR) in which the MM response is adjusted to the relaxed QM density, thus being able to account for charge equilibration in the excited state. The model, which is specified in terms of three physical parameters (electronegativity, chemical hardness, and polarizability) is applied to vacuo-to-water solvatochromic shifts of aqueous solutions of para-nitroaniline, pyridine, and pyrimidine. The results show a good agreement with their experimental counterparts, thus highlighting the potentialities of this approach.

Study of pre-treatment of quinoline in aqueous solution using activated carbon made from low-cost agricultural waste (walnut shells) modified with ammonium persulfate.

Activated carbon made from agricultural waste (walnut shells) was investigated as a suitable adsorbent for effectively removing quinoline from industrial wastewater. The activated carbon was treated with phosphoric acid and oxidized by ammonium persulfate and its ability to adsorb pyridine and quinoline in aqueous solution was investigated. Kinetic parameters for the adsorption process were determined through pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion models. Equilibrium experiments and adsorption isotherms were analyzed using Langmuir and Freundlich adsorption isotherms. After reaching equilibrium, the activated carbon adsorbed quinoline in preference to pyridine: the equilibrium adsorptions from individual aqueous solutions (200 μL L-1) of quinoline and pyridine were 166.907 mg g-1 and 72.165 mg g-1, respectively. Thermodynamic studies of quinoline adsorption were conducted at different temperatures and indicated that quinoline adsorption was an endothermic and spontaneous process. The column-adsorption of quinoline and pyridine was consistent with the Thomas model and the Yoon-Nelson model. The removal efficiency of quinoline reached more than 97% for a velocity of 6 mL min-1 at the initial adsorption stage.

Intermolecular Interactions of Pyridine in Liquid Phase and Aqueous Solution Studied by Soft X-ray Absorption Spectroscopy

Abstract Intermolecular interactions of pyridine in liquid and in aqueous solution are studied by using soft X-ray absorption spectroscopy (XAS) at the C, N, and O K-edges. XAS of liquid pyridine shows that the N 1s→π* peak is blue shifted and the C 1s→π* peak of the meta and para sites is red shifted, respectively, as compared with XAS of pyridine gas. These shifts in liquid are smaller than those in clusters, indicating that the intermolecular interaction of liquid pyridine is weaker than that of pyridine cluster, as supported by the combination of quantum chemical calculations of the core excitation and molecular dynamics simulations of the liquid structure. On the other hand, XAS spectra of aqueous pyridine solutions (C5H5N)x(H2O)1−x measured at different molar fractions show that in the pyridine rich region, x>0.7, the C and N 1s→π* peak energies are not so different from pure liquid pyridine (x=1.0). In this region, antiparallel displaced structures of pyridine molecules are dominant as in pure pyridine liquid. In the O K-edge XAS, the pre-edge peaks sensitive to the hydrogen bond (HB) network of water molecules show the red shift of −0.15 eV from that of bulk water, indicating that small water clusters with no large-scale HB network are formed in the gap space of structured pyridine molecules. In the water rich region, 0.7>x, the N 1s→π* peaks and the O 1s pre-edge peaks are blue shifted, and the C 1s→π* peaks of the meta and para sites are red-shifted by increasing molar fraction of water. The HB network of bulk water is dominant, but quantum chemical calculations indicate that small pyridine clusters with the HB interaction between the H atom in water and the N atom in pyridine are still existent even in very dilute pyridine solutions.

Molecular Dynamics and Neutron Scattering Studies of Mixed Solutions of Caffeine and Pyridine in Water.

Insight into the molecular interactions of homotactic and heterotactic association of caffeine and pyridine in aqueous solution is given on the basis of both experimental and simulation studies. Caffeine is about 5 times more soluble in a 3 m aqueous pyridine solution than it is in pure water (an increase from ∼0.1 m to 0.5 m). At this elevated concentration the system becomes suitable for neutron scattering study. Caffeine-pyridine interactions were studied by neutron scattering and molecular dynamics simulations, allowing a detailed characterization of the spatial and orientational structure of the solution. It was found that while pyridine-caffeine interactions are not as strong as caffeine-caffeine interactions, the pyridine-caffeine interactions still significantly disrupted caffeine-caffeine stacking. The alteration of the caffeine-caffeine stacking, occasioned by the presence of pyridine molecules in solution and the consequent formation of heterotactic interactions, leads to the experimentally detected increase in caffeine solubility.

Hydroxyl multi-walled carbon nanotube-modified nanocrystalline PbO2 anode for removal of pyridine from wastewater

We prepared a hydroxyl multi-wall carbon nanotube-modified nanocrystalline PbO2 anode (MWCNTs-OH-PbO2) featuring high oxygen evolution potential, large effective area, and excellent electrocatalytic performance. The oxygen evolution potential and effective area of the MWCNTs-OH-PbO2 electrode were 1.5 and 3.7-fold higher than the traditional PbO2 electrode. Electrochemical degradation of pyridine in aqueous solution was investigated by using the MWCNTs-OH-PbO2 anode. Based on pyridine decay rate (93.8%), total organic carbon reduction (84.6%), and energy consumption (78.8WhL−1order−1) under the optimal conditions, the MWCNTs-OH-PbO2 electrode modified with MWCNTs-OH concentration of 1.0gL−1 exhibited higher electrochemical oxidation ability than the traditional PbO2 electrode. The intermediate, hydroxypyridine, was found at the first stage of electrolysis. The primary mineralization product, NO3−, was detected in aqueous solution after electrolysis. A possible electrochemical mineralization mechanism including two potential routes, i.e., via formation of small organic molecules by ring cleavage reaction and direct mineralization to CO2 and NO3−, was proposed. The results demonstrated that the MWCNTs-OH-PbO2 electrode exhibited high efficiency for pyridine mineralization in aqueous solution under mild conditions.

Catalytic performance of hierarchical metal oxides for per-oxidative degradation of pyridine in aqueous solution

In present study, we have proposed a generalized template free hydrothermal approach for the synthesis of hierarchical metal oxides (Mn3O4, Co3O4 and NiO) and further used as a catalysts for the degradation of highly toxic heterocyclic compound pyridine from aqueous solution by using the catalytic peroxidation (CPO) method in presence of hydrogen peroxide as an oxidant. The synthesized hierarchical metal oxides (HMOs) catalysts have been characterized by various characterization techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD), field–emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and N2 adsorption–desorption pore size distribution analysis. Characterization results shows that HMOs have higher surface properties and tunable porosity (BET surface area: 233.3–186.4m2g−1, pore volume: 0.88–0.65cm3g−1 and pore size: 6.8–7.4nm). The effects of different operating parameters such as dose of catalysts, H2O2 concentration, initial pyridine concentration, solution pH, and treatment temperature have been studied and optimized the CPO method for pyridine removal. More than 90–95% pyridine and 85–90% total organic carbon (TOC) were removed at the optimum condition. The qualitative and quantitative analysis of intermediates byproducts formation and their final products generation was determine by high performance liquid chromatography (HPLC), gas chromatography–mass spectrometry (GC–MS), ion chromatography (IC) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). A plausible degradation pathway has been proposed on the basis of the results of analysis. Synthesized HMOs presented the stable performance throughout the reuse for five cycles with negligible metals leaching. Kinetics and thermodynamic study of the parameters have also been evaluated.

Chemiresistors based on ultrathin gold nanowires for sensing halides, pyridine and dopamine

Two distinctively different approaches to the deposition of the ultrathin gold nanowires (NWs) on chips for the development of the chemiresistor sensors are studied. The first approach is the deposition of the pre-synthesized NWs on a chip using a microfluidic technique, and the second is the direct synthesis of the NWs on chips. It is shown that the 2nd approach ensures a better contact between the NWs and electrodes, lower resistance of the NW sensor device, and a longer life time of the devices. The current-voltage dependencies obtained for the chips with the NWs in contact with air, and aqueous solutions of NaF, NaCl, NaBr, NaI, pyridine, and dopamine indicate significant changes of the NWs resistance caused by sorption of halides, pyridine and dopamine on the NWs surface. This change of the NWs resistance can be used for quantification of Cl− over a concentration range of 10−5–10−3M and dopamine over a concentration range of 10−8–10−5M. Tentatively, it is concluded that the data obtained can be explained in terms of the Langmuir adsorption isotherm.

Development and application of in situ/operando soft X-ray transmission cells to aqueous solutions and catalytic and electrochemical reactions

In this review, we have demonstrated several applications of newly-developed in situ/operando liquid flow cells for the transmission XAS (X-ray absorption spectroscopy) measurement in the soft X-ray undulator beamline BL3U dedicated to the chemical application of UVSOR-III Synchrotron. The liquid layer is sandwiched between two thin membranes and its thickness is easily controllable to optimize the absorbance. Liquid samples are exchangeable in situ. Molecular spectra in liquid and gas phases are simultaneously measureable and it makes the energy calibration rather easy. By using a standard version of the liquid cells, we have investigated local structures of several aqueous solutions of alkali halides, methanol, pyridine, and acetonitrile. To observe catalytic and electrochemical reactions under realistic conditions, we have developed in situ/operando versions of the liquid cells. We have investigated local structures of the catalytic hydration reaction of cyanopyrazine under the temperature control and the electrochemical reaction of aqueous iron sulfate solutions using the built-in electrodes under the same scan rate as in cyclic voltammetry. We have discussed future perspectives of our in situ/operando liquid flow cells applied to XAS in the soft X-ray region.

Application of Ultraviolet and Ultrasound Irradiation for the Degradation of Pyridine in Wastewater: A Comparative Study

The photochemical and sonochemical degradation of aqueous solutions of pyridine, a common refractory pollutant in wastewater effluents, have been investigated by means of ultraviolet (UV), ultrasound (US), UV/H 2 O 2 , and US/H 2 O 2 irradiation processes. The pure photochemical process were demonstrated to be efficient for degradation of low initial concentrations of pyridine (10 ppm). Sonochemical degradation proceeded very slowly, leading to less than 53% of pyridine removal after 200 min. The degradation efficiency was increased with increasing H 2 O 2 concentration; however, the marginal benefit became decreasing with further increasing of H 2 O 2 due to the scavenging effect of excess H 2 O 2 . The kinetics of photochemical and sonochemical degradation of pyridine were found to follow a first-order rate law. A possible degradation pathway for pyridine was also proposed.

Self-association of sulfo derivatives of cobalt phthalocyanine in aqueous solution

Sulfo derivatives of cobalt phthalocyanine containing naphthalene fragments have been synthesized, and their self-association and molecular complexation with pyridine in aqueous solution have been studied by spectrophotometry. The dissociation constants of the dimeric associates have been determined. The effects of the number of functional groups in the peripheral substituents and of the axial ligand on the phthalocyanine dimerization process have been revealed.

Successive advanced oxidation of pyridine by ultrasonic irradiation: effect of additives and kinetic study

Pyridine has received considerable attention from environmental scientists and engineers, due to its undesirable effect in the water environment. Pyridine contaminated wastewater presents a great threat on water resources safety. In this research, the degradation and advanced oxidation of pyridine in aqueous solution by ultrasonic waves were studied under various process variables including different initial concentration, H2O2, NaCl, and Fenton reagent. The results show that the degradation efficiency of pyridine decreases with the increasing of the initial concentration of pyridine. The removal rates of pyridine decreased from 52 to 15% with increasing the initial concentration from 10 to 100 mg/L. In the concentration range studied, the amount of H2O2 and NaCl added has positive contribution on the degradation of pyridine. The removal effect of ultrasound and Fenton is better than ultrasound or H2O2 alone acting on pyridine. A possible degradation pathway for pyridine was also proposed. In the end, it could be proposed that ultrasonic irradiation was an effective method for the removal of pyridine from wastewater.

ChemInform Abstract: Oxidation of Alcohols and Pyridines by a Water‐Soluble Polyoxometalate with Hydrogen Peroxide.

AbstractK8[β‐SiW11O39]·14 H2O is used as catalyst for the oxidation of alcohols and pyridines in aqueous solution using hydrogen peroxide as the oxidant.

A new structural technique for examining ion-neutral association in aqueous solution

The method of intramolecular coordination number concentration invariance (ICNCI) is used on neutron diffraction with isotopic substitution (NDIS) measurements of aqueous solutions to separate the intra- and intermolecular contributions to the total intensities. Molecular dynamics simulations of corresponding systems are then used to interpret the ICNCI function. It is found that the ICNCI function (characterized by two concentration measurements) is sensitive specifically to intermolecular association and that the molecular dynamics can successfully replicate this function in the cases of the neutral species xylose and pyridine in aqueous solution. ICNCI functions can also be obtained by the addition of a cosolute (such as adding GdmCl or Gdm2SO4 to pyridine solutions). In that case it is found that molecular dynamics can replicate the ICNCI function for the addition of GdmCl to pyridine, but fails to successfully replicate the same function for the addition of Gdm2SO4. This result implies that the interaction of pyridine with guanidinium sulfate is over-estimated in these MD simulations, and is of significant importance to the use of molecular dynamics simulations to elucidate an atomic level understanding of the Hofmeister series.

Water-induced aggregation and hydrophobic hydration in aqueous solutions of N-methylpiperidine

Liquid system N-methylpiperidine–water shows a miscibility gap with a lower critical solution temperature of 316.7 K. The phase separation is most likely due to the aggregation of N-methylpiperidine–water complexes, evident in the intensity of the small-angle neutron scattering at temperatures much lower than the LCST. Such complexes arise because the attraction forces between unlike molecules are stronger than the water–water ones, and aggregation is possible through the O–H⋯O bonds involving the hydration water molecules. The aggregates are dynamic structures with nanoseconds-order relaxation times, as it was estimated by the ultrasonic absorption experiment. While hydrophilic aggregation prevails at relatively high concentrations of the amine, the hydrophobic hydration is possible at low concentrations, likely consisting of the formation of structures resembling those in the sH clathrates observed in the solid state. The hydrophobic hydration of N-methylpiperidine is manifested in the minima of the partial volume isotherms at the amine mole fraction close to 0.01 and in the limiting partial molar compression approximately equal to zero. Essential similarity of the N-methylpiperidine–water system to aqueous solutions of pyridine and its methyl derivatives studied previously, suggests that those amines are potential clathrate hydrate promoters.

A comparative study of the volumetric properties of aqueous solutions of pyridine and piperidine derivatives

The objective of this research was to carry out a comparative study of the volumetric properties of 2-pyridinemethanol, 3-pyridinemethanol, 2-(hydroxymethyl)piperidine, and 3-(hydroxymethyl)piperidine in aqueous media. The density and excess volumes of mixing as a function of temperature (T=293.15–318.15K) over the entire concentration range are examined for aqueous solutions of 2,3-pyridinemethanols, and the density and partial molar volumes of aqueous solutions are investigated for the corresponding 2,3-(hydroxymethyl)piperidines. The minimum values of the excess molar volumes, vE, are observed, −0.59cm3mol−1 for 2-pyridinemethanol–water solutions and −0.47 for 3-pyridinemethanol–water solutions. These are about 0.61% and 0.49% respectively, of the molar volume. The thermal expansion coefficients αT at 298.15K calculated from the density data, exhibited significant positive deviations, (about 30%) from ideality for 2-pyridinemethanol–water mixtures, and 3-pyridinemethanol–water mixtures. The partial molar volume of 2,3-(hydroxymethyl)piperidines in water at selected temperatures was evaluated by extrapolating the apparent molar volume versus molality plots to m=0. In addition, the partial molar expansivity, E0, the isobaric coefficient of thermal expansion, αT, the interaction coefficient, Sv, and the Hepler's constant have also been computed. The data are interpreted in terms of the effect of the primary alcohol functional group on the inter/intramolecular and additional hydrophilic interactions between the molecules.

Plasmon Waveguide Resonance Raman Spectroscopy

Raman spectra were collected from a 1.25 M aqueous pyridine solution, 100-nm polystyrene film or a trimethyl(phenyl)silane monolayer at a plasmon waveguide interface under total internal reflection (TIR). The plasmon waveguide resonance (PWR) interface consisted of a sapphire prism/49 to 50 nm Au/548 to 630 nm SiO(2) and a monolayer, thin film or aqueous analyte. The Raman peak area as a function of incident angle was measured using a 785-nm excitation wavelength, and was compared to the Raman peak area obtained at a sapphire or sapphire/50 nm Au interface. In contrast to measurements at a bare sapphire prism, increased surface sensitivity and signal were obtained from the PWR interface. In contrast to measurements at a bare Au film where only p-polarized incident light generates an enhanced interfacial electric field, plasmon waveguide interfaces enable excitation with orthogonal polarizations using s- or p-polarized incident light. The Raman scatter from a monolayer was recorded at the PWR interface with a signal-to-noise ratio of 5.6 when averaging 3 accumulations with 3 min acquisition times using nonresonant excitation, whereas no signal was recorded from a monolayer at the sapphire interface. The reflected light from the interface enabled the identification of the incident angle where the maximum Raman scatter was produced, and the Raman signal generated at the plasmon waveguide interface was modeled by the enhanced interfacial mean square electric field relative to the incident field. In comparison to the techniques on which this work was based (i.e., PWR spectroscopy, TIR Raman spectroscopy at the prism interface, and surface plasmon resonance (SPR) Raman spectroscopy at the prism/Au interface), chemical specificity was added to PWR spectroscopy, a signal enhancement mechanism was introduced for TIR Raman spectroscopy, and polarization control of the interfacial electric field was added to SPR Raman spectroscopy.

Catena-bis(aqua(3-oxy-2-pyridono)copper(II))μ-pyrazine diperchlorate: a perchlorate-bridged magnetic ladder

Reaction of Cu(ClO4)2 · 6H2O with pyrazine (pz) and 2,3-dihydroxy pyridine in aqueous solution generates bis(aqua(3-oxy-2-pyridono)copper(II))μ-pyrazine diperchlorate. The compound crystallizes in the triclinic space group P 1. The aqua(3-oxy-2-pyridono)copper(II) units are bridged by pyrazine to form a dimer. These dimers are further bridged by perchlorate to form a structural ladder parallel to the b-axis. Hydrogen bonding interactions and π-stacking of the pyridone rings also provide structural stability to the lattice and provide potential magnetic superexchange pathways. Temperature-dependent magnetic susceptibility data reveal a maximum in χ near 6 K and exhibit a rapid drop in χ at lower temperatures, in agreement with a singlet ground state. The use of several models for fitting the magnetic data gave values of approximately −10 K for the dimer interaction and approximately +1.5 K for the interdimer interaction.