Quaternary Nitrogen Research Articles

Adsorption of a cationic surfactant, miramistin, from aqueous solutions on the surface of highly dispersed silica

The adsorption of a universal antiseptic agent, the cationic surfactant miramistin, on the surface of highly dispersed silica has been studied. It has been shown that, when miramistin is adsorbed from acidic premicellar solutions, the main contribution to miramistin binding with the surface is made by hydrogen bonding between amide groups of surfactant molecules and silanol groups of silica, which is, at higher pH values, accompanied by ionic interaction between positively charged quaternary nitrogen atoms of miramistin and negatively charged dissociated silanol groups. In the case of adsorption from a micellar solution, an increase in the surface concentration of miramistin is almost independent of solution pH, because the second layer is predominantly formed due to hydrophobic interactions.

Effect of heating rate on migration and transformation of N during pyrolysis of Shengli brown coal

The effects of heating rate on migration, transformation and occurring forms of nitrogen during pyrolysis of Shengli brown coals were studied in a fixed-bed/fluidised-bed quartz reactor. The results indicate that the yields of NH3 and HCN from the fast pyrolysis were much higher than those from the slow pyrolysis. The difference in the yields of NH3 and HCN between the fast and slow heating rates increases with the increasing pyrolysis temperature. The maximum productions of NH3 and HCN mostly occur at 973 K, which is attributed to the enhanced condensation and secondary reactions with the increasing pyrolysis temperature. The release rate of char-N is faster than the weight loss rate of char itself at fast heating rate. The results from X-ray photoelectron spectroscopy (XPS) analysis imply that the pyrolysis process has facilitated the transformation of pyrrolic (N-5) to quaternary type nitrogen (N-Q) and pyridinic (N-6). It seems that the fast heating rate favors the formation of N-6 while the content of N-Q in char is relatively high at the slow heating rate.

Analysis of forming process of nitrogen-doped carbon catalyst derived from Fe 1,10-phenanthroline compound and its oxygen reduction reaction activity

The pyrolysis behavior of iron 1,10-phenanthroline compound, the change of crystalline structure of iron in the iron 1,10-phenanthroline compound, and nitrogen chemical state of nitrogen doped carbon catalyst derived from iron 1,10-phenanthroline compound were investigated to clarify the process of improvement of oxygen reduction reaction (ORR) activity on nitrogen-doped carbon catalyst by TGA, EGA-MS, HT-XRD, XRD, and XPS technique. The ORR activity drastically improved at a synthesis temperature of 700 °C, and was the highest at a synthesis temperature of 800 °C. But the ORR activity significantly dropped at a synthesis temperature of 900 °C. This low ORR activity of NC-900 is probably due to the increase of quaternary nitrogen ratio with progression of excessive carbonization, and the quaternary nitrogen to pyridine-like nitrogen ratio might be an important factor for improvement of the ORR activity.

Formal Redox Potentials of Organic Molecules in Ionic Liquids on the Basis of Quaternary Nitrogen Cations as Adiabatic Electron Affinities

Formal redox potentials E°' involving neutral species R and radical anions R(•-) in ionic liquids (ILs) composed of ammonium, pyridinium, and imidazolium cations are discussed from the point of view of the adiabatic electron affinity as a molecular property. The dependence of the 1,4-benzoquinone (BQ)/BQ(•-) redox process in CH2Cl2 and CH3CN is primarily investigated over a wide concentration range of ILs as the supporting electrolyte. A logarithmic relationship involving a positive shift of E°' with increasing concentration is obtained when the concentration is changed from 0.01 to 1.0 M. The relationship of E°' at IL concentrations greater than 1.0 M gradually reaches a plateau and remains there even for the neat ILs. It is found that the E°' values in the neat ILs are not influenced by the measurement conditions, and that they remain considerably dependent on the nature and concentration of the electrolyte when measured using the traditional method involving molecular solvents combined with a supporting electrolyte (0.1-0.5 M). The difference in the E°' values observed in the ammonium and pyridinium ILs is only several millivolts. In addition, ESR and self-consistent isodensity polarized continuum model calculation results reveal that the potential shift toward positive values upon the transition from molecular solvents containing ILs to neat ILs is adequately accounted for by changes in the electrostatic interaction of R(•-) taken into the cavity composed of the solvent and IL. On the other hand, the first reduction waves of quinones, electron-accepting molecules, and polynuclear aromatic hydrocarbons are reversibly or quasi-reversibly observed in the ILs. The electrochemical stability of the ILs is exploited in the facile measurement of these quasi-reversible waves at quite negative potentials, such as for the naphthalene (NP)/NP(•-) couple. Notably, the E°' values obtained in the ammonium ILs correlate well with the calculated standard redox potentials and are linearly fitted with high correlation over all classes of compounds using a single regression equation based on Koopmans' theorem.

Room temperature thermotropic liquid crystalline phases of catanionic surfactants derived from quaternary ammonium surfactants and bis(2-ethylhexyl)sulfosuccinate

HypothesisProperties of catanionic surfactants can be tailored by the choice of appropriate headgroups and hydrocarbon tails. Thermal behavior of catanionic surfactants can be influenced by the length and number of alkyl chains. ExperimentsA series of eight catanionic surfactants were synthesized from quaternary ammonium surfactants as the cationic counterpart and bis(2-ethylhexyl)sulfosuccinate (AOT) as the anionic counterpart. The thermal properties and the liquid crystalline properties of these catanionic surfactants were studied by the following methods: Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Hot-Stage Polarized Light Microscopy (HSPLM), and X-ray Diffraction (XRD). FindingsThe results indicate that transition temperatures, enthalpies of transition, and mesophase structures vary with the length and number of chains attached to the quaternary nitrogen. These compounds exhibit room temperature liquid crystalline (LC) textures that are predominantly “fan-like,” as observed by HSPLM, and phases that are hexagonal columnar, as observed by XRD, with the exception of one compound which exists as a nematic liquid crystal at 25°C. Additionally, all of the surfactants also exhibit thermal stability in the range of 256–300°C.

Cationised O-acetyl galactoglucomannans: Synthesis and characterisation

Water-soluble O-acetyl-galactoglucomannans (GGMs) can be obtained from Norway spruce by hot-water-extraction of the wood or as a side product by ultrafiltration of mechanical pulping waters. Cationic and amphiphilic polysaccharides and their derivatives are of interest for a number of applications and thus quaternary nitrogen moieties with cationic charge were grafted onto GGMs in the heterogeneous reaction to render a cationic polyelectrolyte. The degree of substitution was measured by elemental analysis of nitrogen, by quantitative 13C NMR and interestingly also by polyelectrolyte titration and the results were congruent. NMR, matrix-assisted laser desorption/ionisation mass spectroscopy (MALDI-TOF-MS), and FT-IR analysis were used to characterise the product. THF or DMSO with water enhanced the reaction efficiency and decreased Mw reduction in comparison to plain water as a reaction media. Cationised GGM was also successfully acetylated. The cationic derivatives of hemicelluloses can potentially be utilised as polyelectrolyte layers in packaging and pharmaceutical applications.

Fluorinated Quaternary Ammonium Bromides: Studies on Their Tetrahydrofuran Hydrate Crystal Growth Inhibition and as Synergists with Polyvinylcaprolactam Kinetic Gas Hydrate Inhibitor

Fluorinated low-dosage hydrate inhibitors (LDHIs) have been investigated for the first time. Three novel quaternary ammonium salts with monofluorobutyl groups were synthesized and characterized, N-(4-fluorobutyl)-N,N-dipentylpentan-1-aminium bromide (2), N,N-bis(4-fluorobutyl)-N-pentylpentan-1-aminium bromide (3), and N,N,N-tris(4-fluorobutyl)pentan-1-aminium bromide (4). It was investigated whether these fluorinated ammonium salts, in which a fluorine atom replacing an end methyl group in the alkyl chains of tetra(n-pentyl)ammonium bromide (TPAB), would affect tetrahydrofuran (THF) hydrate crystal growth inhibition. We determined that the monofluoro ammonium salt N-(4-fluorobutyl)-N,N-dipentylpentan-1-aminium bromide (2) was the best THF hydrate crystal growth inhibitor, showing better performance than either TPAB or tetra(n-butyl)ammonium bromide (TBAB). However, THF hydrate crystal growth inhibition decreased as the number of fluorobutyl groups on the quaternary nitrogen atom was increased to two or three. In addition, we observed that the monofluoro ammonium salt (2) was a better kinetic hydrate inhibitor synergist than TPAB in combination with poly(N-vinyl caprolactam) (PVCap) under high-pressure rocking cell tests using a structure-II-forming natural gas mixture. The difluoro and trifluoro salts (3 and 4) were poorer synergists in keeping with the trend from the THF hydrate crystal growth experiments. A mechanism to explain these results is proposed.

Use of Pyrolyzed Iron Ethylenediaminetetraacetic Acid Modified Activated Carbon as Air–Cathode Catalyst in Microbial Fuel Cells

Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m(2), which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m(2)) and comparable to Pt cathodes (1550 ± 10 mW/m(2)). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC.

Separation of TiO2 particles from water and water/methanol mixtures by cationic dextran derivatives

Cationic polysaccharides with N-alkyl-N,N-dimethyl-N-(2-hydroxypropyl)ammonium chloride pendent groups attached to a dextran backbone were used to flocculate titanium dioxide (TiO2) particles suspended in water as well in water/methanol mixtures (90:10 and 50:50 v/v %). The investigations were performed with respect to the polycation dose, the suspension medium composition and the length of alkyl substituent at the quaternary nitrogen (alkyl=ethyl, octyl, dodecyl). The supernatant residual turbidity values were much lower for TiO2 particles dispersed in solvent mixtures than in water. This finding was explained by the solvent mixtures effect on the charges of both the particle surface and polyelectrolyte chains. The alkyl substituent length did not affect in a dramatic way the separation of TiO2 particles. The supernatant zeta potential dependence on the polycation dose when water/methanol mixtures were used as dispersion medium indicated a charge patch mechanism for the flocculation of TiO2 particles, which was supported by particle aggregates size measurements.

New quaternary ammonium camphor derivatives and their antiviral activity, genotoxic effects and cytotoxicity

The synthesis and biological evaluation of a novel series of dimeric camphor derivatives are described. The resulting compounds were studied for their antiviral activity, cyto- and genotoxicity. Compounds 3a and 3d in which the quaternary nitrogen atoms are separated by the C5H10 and С9H18 aliphatic chain, exhibited the highest efficiency as an agent inhibiting the reproduction of the influenza virus A(H1N1)pdm09. The cytotoxicity data of compounds 3 and 4 revealed their moderate activity against malignant cell lines; compound 3f had the highest activity for the CEM-13 cells. These results show close agreement with the data of independent studies on toxicity of these compounds, in particular that the toxicity of compounds strongly depends on spacer length.

Nitrogen plasma functionalization of carbon nanotubes for supercapacitor applications

Surface modification of carbon nanotubes with a simple and fast plasma treatment allows for the design of new nanomaterials with enhanced electrochemical properties. Both structural disorder and nitrogen concentration of the nanotubes increase after a nitrogen plasma treatment. The effect of plasma power and nitrogen pressure on the charge storage capability of the nanotubes has been investigated in detail. Depending on the plasma conditions, nitrogen functionalities such as quaternary nitrogen in the basal planes, and pyrrolic groups at the edges are introduced in the nanotubes structure. The potential difference between anodic and cathodic peaks of the Fe3+/Fe2+ redox couple decreases from 102 mV down to 75.7 mV after the nitrogen plasma treatment, which accounts for an increased reversibility of the electron transfer process between nanotubes and electrolyte. Moreover, the treated nanotubes show a significant increase in their specific capacitance from 22 up to 55 F g−1 at a scan rate of 10 mV s−1 in a 0.1 M Na2SO4 solution. Pyridinic and pyrrolic functionalities are found to play an important role in enhancing the reversibility and specific capacitance of the obtained electrodes.

Novel Conjugated Quinoline–Indoles Compromise Plasmodium falciparum Mitochondrial Function and Show Promising Antimalarial Activity

A novel class of antimalarial compounds, based on an indol-3-yl linked to the 2-position of a 4-aminoquinoline moiety, shows promising activity against the malaria parasite, Plasmodium falciparum . Compounds with a quaternary nitrogen on the quinoline show improved activity against the chloroquine-resistant K1 strain. Nonquaternerized 4-aminoquinolines retain significant potency but are relatively less active against the K1 strain. Alkylation of the 4-amino group preferentially improves the activity against the chloroquine-sensitive 3D7 strain. The quinoline-indoles show only weak activity as inhibitors of β-hematin formation, and their activities are only weakly antagonized by a hemoglobinase inhibitor. The compounds appear to dissipate mitochondrial potential as an early event in their antimalarial action and therefore may exert their activity by compromising Plasmodium mitochondrial function. Interestingly, we observed a structural relationship between our compounds and the anticancer and anthelminthic compound, pyrvinium pamoate, which has also been proposed to exert its action via compromising mitochondrial function.

A First-Principles Study of the Role of Quaternary-N Doping on the Oxygen Reduction Reaction Activity and Selectivity of Graphene Edge Sites

Density functional theory (DFT) was used to investigate O2 chemisorption on the edge sites of graphene doped with quaternary nitrogen (N-graphene). The location of the doped quaternary N within the graphene cluster was systematically varied to determine the effect of interior versus edge doping on the reactivity of the edge graphene sites. Model 1b, where a quaternary-N atom is at the zigzag edge of the graphene cluster, is found to be the most favored structure and strongly adsorbs O2 molecule via a “two feet” geometry. For this most stable O2 binding configuration, the potential-dependent free energy of reaction for the subsequent oxygen reduction reaction (ORR) steps was evaluated. The favored four electron-proton transfer mechanism passes through a dissociative O*+OH* state instead of an OOH* intermediate, followed by a series of reduction steps to produce water. At the equilibrium potential for ORR of 1.23 V-NHE, the protonation of O* and OH* both show uphill steps, but the production of O* is facile with a small overpotential. An applied potential of −0.15 V-NHE is required to facilitate the protonation of OH* to water, a larger overpotential than observed experimentally. While solvent effects may reduce this overpotential, our results suggest that the edge of the N-graphene is very active towards activation of O2 and production of O* and OH* but because of strong binding of the oxygen atom, the subsequent steps of the ORR reaction will be hindered. Mechanisms that have OH* formed at the edge site and then move to adjacent sites for more facile protonation will have to be explored in the future.

Complexes of carboxyl-containing polymer and monosubstituted bipyridinium salts

Semi-empirical PM3 method for the quantum calculations of molecular electronic structure based on NDDO integral approximation is used to investigate the complex formation of monosubstituted 4,4′-bipyridinium salts BpyR (Hal) containing a halide anion interacting with the quaternary nitrogen atom and carboxylic group of the two-units construct. Significant effect of the BpyR (Hal) electronic structure is unveiled that contributes in two different structures of these salts, namely, partial charge transfer complex and ion pair structure, both having stable energy minima. We demonstrate that (i) the structure of the N-substituent modulates the energy and electronic characteristics of monosubstituted salts BpyR with chlorine and bromine anions and (ii) the coulomb interactions between quaternary N-atom, halogen anion, and the proton of carboxylic group stimulate the transformation of the charge transfer complex into the ion pair structure. Results of calculations are compared with the experimental FTIR spectra of blends of BpyR(Hal) with Eudragit copolymer.

Porous nitrogen-doped carbon nanofibers as highly efficient metal-free electrocatalyst for oxygen reduction reaction

Three kinds of polymer blend of poly(methyl methacrylate) (PMMA)/polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP)/PAN and cellulose acetate (CA)/PAN were converted into nitrogen-doped carbon nanofibers (NCNFs) by electrospinning combined with acid oxidation and NH3 etching. The NCNFs showed excellent electrocatalytic performance for oxygen reduction reaction (ORR) in acid media, probably being attributed to the good hydrophilicity and wettability, porous fibrous structure, ultra thin diameter of less than 50nm, more exposed edge planes of pyrolytic graphitic carbons, and high proportion of pyridinic and quaternary nitrogen. The developed NCNFs show great potential as metal-free electrocatalyst for ORR in acid environment.

Paraquat-Induced Ultrastructural Changes and DNA Damage in the Nervous System Is Mediated via Oxidative-Stress-Induced Cytotoxicity in Drosophila melanogaster

Paraquat (PQ), a quaternary nitrogen herbicide, is commonly used as a pesticide despite of its high toxicity. Our study evaluated the effect of subchronic PQ exposure on the neuropathology, genotoxicity, and antioxidant activity on the nervous tissue of Drosophila melanogaster. We also explored the behavioral effect of PQ on D. melanogaster. Furthermore, we attempted to validate the mechanism by evaluating PQ-induced cytotoxicity on the D-Mel2 cell lines. The fruit fly D. melanogaster serves as a feasible model to understand the mechanism of neurodegenerative diseases. Our study shows a dose-dependent PQ-induced neuropathology in the brain tissue of D. melanogaster as evidenced by hematoxylin and eosin staining, silver nitrate staining, and transmission electron microscopy. Electron microscopic study of D. melanogaster brain tissue exhibited vacuolar degeneration and significant neuronal damage across the nervous tissue structure in comparison with control. Our findings also indicate a dose-dependent locomotor impairment and decreased superoxide dismutase (SOD) specific activity in PQ-treated D. melanogaster. These PQ-induced neuroanatomical changes and decreased SOD specific activity showed a significant association with oxidative DNA damage as observed by alkaline comet assay. Additionally, we show, for the first time, a dose-dependent PQ-induced cytotoxicity in the D-Mel2 cells suggesting loss of neuronal cell viability via cytotoxic damage. Our data suggest that PQ exposure results in neurodegeneration in D. melanogaster and that fruit fly is a suitable in vivo model for correlating the neuroanatomical changes with neurotoxic damages to nervous system.

Effects of ammonization on the surface physico-chemical properties of sludge-based activated carbon

In this paper, sludge-based activated carbon (SAC) was treated by HNO3 and NH3 in turns. Under the conditions of ammonization temperature and residence time, the surface physico-chemical characteristics of modified SAC were characterized by SEM, BET, FTIR and XPS. The research results show that modification of SAC leads to beneficial effect on the porous structure, the maximum surface area and micro-pore volume reached to 273m2/g and 0.082cm3/g at 750°C, respectively. After ammonization, NCH3 and CN groups were detected on the surfaces of all the modified SACs. Moreover, XPS study indicated that the nitrogen content increased from 1.65% in origin sample to a larger content range of 2.93–4.69% at different treatment conditions and found that lower ammonization temperature and longer residence time will produce higher nitrogen content. The nitrogen introduced mainly in the forms of amines, pyridine nitrogen (N-6), pyrrole nitrogen (N-5), quaternary nitrogen (N-Q) and N-pyridine oxide (N-Ox). The sample of SAC-650-90 obtained the highest content of N-6 with the value of 1.46%. The highest content of N-5, N-Q and N-Ox which obtained in the sample of SAC-750-120 in the same time were 1.22%, 0.98% and 1.21%, respectively. Compared to the ratios of five kinds of nitrogenous substance, the highest ratios of N-Ox, N-5, N-Q and N-6 obtained among different samples were 27.11%, 29.09%, 33.14% and 31.11%, respectively. And they can transform from one type to another.

Identifying the Active Site in Nitrogen-Doped Graphene for the VO2+/VO2+Redox Reaction

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.

Competition between substitution and elimination reaction channels from fragmentation ratios of diquaternary ammonium bromide and formate ion pairs

Fragmentation by collisionally induced dissociation in triple quadrupole mass spectrometer of pairs of six series of quaternary diamines (gemini surfactants) with two anions: formate and bromide has been studied. Amines included alkanediyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium bromide), alkanediyl-α,ω-bis-(N-hydroxyethyl-N-methyl-N-dodecyl ammonium bromide), oligo(oxa)ethyl-α,ω-bis-(N,N-dimethyl-N-dodecyl ammonium bromide) and three series of hexadecyl homologues. Range of atoms forming spacer varied from 2 to 23. It was confirmed that fragmentation occurs via either nucleophilic substitution or elimination reactions. All possible α-carbon atoms can be attacked in the substitution reaction, so can be all possible hydrogens of β-carbon in the elimination reaction. Additionally transferred to anion can be hydroxy group hydrogen. It leads together to eight different reaction paths. Depending on the spacer size and the kind of anion the ratio of fragmentation channels varies dramatically. For short spacers length ion pairs with formic anion dissociate through elimination, while bromide through substitution at spacer carbon. When spacer length is long enough to accommodate central anion between two quaternary nitrogens the substitution channel becomes the dominating one for both anions with exception when one of the substituents is hydroxyethyl. Then elimination is the only channel for ion pairs with formate anions, but for bromide anion division between substitution and elimination channels is not much affected. From the trends in channel ration and additional experiment with asymmetric geminis reveal it was concluded that the transition state is probably substantially different for long and short spacer geminis.

Cyclopolymerization protocol for the synthesis of a new poly(electrolyte-zwitterion) containing quaternary nitrogen, carboxylate, and sulfonate functionalities

A new zwitterionic monomer, N-carboethoxymethyl-3-(N,N-diallylamino)propanesulfonate, on cyclopolymerization in aqueous solution using tert-butyl hydroperoxide, afforded a polyzwitterion (PZ) which on acidic hydrolysis of the ester groups led to the corresponding polyzwitterionic acid (PZA). The pH-responsive PZA on treatment with sodium hydroxide gave a new poly(eletrolyte-zwitterion) (PEZ) in excellent yield. The solution properties of the salt-tolerant PZ, PZA and PEZ were studied in some detail. Unlike common polyzwitterions, PZ and PZA were found to be soluble in salt-free as well as salt-added water. The apparent basicity constants of the carboxyl group in PEZ have been determined in salt-free water and 0.1M NaCl. The poly(electrolyte-zwitterion) (PEZ), as the name implies, possesses dual type of structural character common to both conventional anionic polyelectrolytes and polyzwitterions, and its aqueous solution behavior is found to be similar to that observed for a typical alternating anionic–zwitterionic copolymer.