Cation Chemistry Research Articles

Birch encroachment affects the base cation chemistry in a restored bog

ABSTRACTIn this study, we compared non‐forested and forested habitat types of a degraded bog in Western Germany with regard to the base cation chemistry of their pore waters. Peat profiles were sampled in 10‐cm intervals every month from April to July 2009 down to a maximal depth of 150 cm. Pore waters were analysed for Ca, Mg, K and Na concentrations. Additionally, electrical conductivity and pH were measured in surface pools. Both habitat types were sampled with four replicate plots, showing the same vegetation structure.Strong differences were found between the concentrations and distributions of base cations in the pore water profiles from the different habitat types. The forested sites revealed higher concentrations for all base cations, but especially for Ca and Mg. Seasonality had an effect on element distributions in pore waters, but its influence was particularly strong at the forested sites. Element distributions and seasonality were caused by several interacting biological and physicochemical processes, such as plant uptake and mineralization or evaporative enrichment and dilution by rainwater. Concludingly, we draw implications for bog restoration and for the use of element ratios as criterion of mineral influence on bog waters. Our study clearly demonstrates the enhancement of base cation supply by birch encroachment, which is posing an additional burden on successful bog restoration. Additionally, the importance of an intact buffer zone around restored peat bogs is underlined. Copyright © 2013 John Wiley & Sons, Ltd.

Microwave-assisted solution combustion synthesis of high aspect ratio calcium phosphate nanoparticles

Abstract

Unleashing radical sites in non-covalent complexes: The case of the protonatedS-nitrosocysteine/18-crown-6 complex

Introducing radicals onto gas-phase non-covalent complexes and studying their chemistry is a relatively unexplored frontier. In generating these radicals via bond homolysis reactions, it is important that the energy necessary for forming the radical does not exceed the energy required for dissociating the complex itself. Based on this consideration, new approaches for creating these radicals will probably have to involve incorporation of weak bonds that can easily undergo homolysis. The formation of a radical cation, via collision-induced dissociation, of protonated S-nitrosocysteine non-covalently bound to the crown ether 18-crown-6 is described here. The radical cation of this complex was isolated and subjected to collisional activation and ion-molecule reactions with allyl iodide. The results were compared with those of the radical cation of 'bare' cysteine. Collisional activation of the radical cation of the cysteine/crown complex led to fragmentation of cysteine as well as of the crown ether. Ion-molecule reactions of the radical cation of the complex with allyl iodide led to products arising from I and allyl abstraction. Isolation and CID of the former product ion led to the loss of iodocysteine. Cleavage of the weak S-NO bond has allowed the formation of a radical site onto a non-covalent complex. Ion-molecule reactions and collisional activation were utilized to probe the chemistry of this radical cation. The approach adopted here for incorporating a radical onto a cysteine/crown complex shows promise for the introduction of radical sites onto other biological non-covalent complexes.

Acetone cation chemistry under varying electron density conditions: from unimolecular decomposition to dissociative recombination processes

The chemistry of ionized acetone:Ar mixtures under varied ionizing electron density conditions has been studied using matrix-isolation techniques. Gaseous acetone diluted in excess argon gas was subjected to electron bombardment with 300 eV electrons at currents between 20 and 200 μA. Linear wire 'pin' and metal 'plate' electron collector geometries were employed, allowing a wide range of electron density conditions to be explored. The products of subsequent reaction processes were matrix isolated and analyzed by Fourier transform infrared absorption spectroscopy. Products included methane, ketene, 1-propen-2-ol (the enol isomer of acetone), CO, HCO, ethane, ethane, acetylene and CCCO. Product absolute and relative yields varied with acetone number density, the choice of anode geometry and the rate of electron bombardment. The overall chemistry observed is rationalized in terms of mechanistic steps involving unimolecular cation decomposition, ion-molecule reactions, radical-radical reactions and dissociative recombination processes.

The chemistry of amine radical cations produced by visible light photoredox catalysis

Amine radical cations are highly useful reactive intermediates in amine synthesis. They have displayed several modes of reactivity leading to some highly sought-after synthetic intermediates including iminium ions, α-amino radicals, and distonic ions. One appealing method to access amine radical cations is through one-electron oxidation of the corresponding amines under visible light photoredox conditions. This approach and subsequent chemistries are emerging as a powerful tool in amine synthesis. This article reviews synthetic applications of amine radical cations produced by visible light photocatalysis.

Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.

Development of Water Quality Index (WQI) model for the groundwater in Tirupur district, South India

Groundwater quality of the Tiruppur district in Tamil Nadu was investigated in this study to develop a Water Quality Index (WQI) model. Hydrochemical parameters showed tremendous variation in certain location over the seasons. Ionic chemistry of groundwater suggested that textile industries and rock-water interaction are major threats to the water quality. Analysis of Na and Ca concentration indicates that direct as well as the inverse cation exchange controls the natural cation chemistry. NO3 concentration shows that the pre-monsoon samples were affected by the fertilizer usage in agricultural fields. Na-Cl type of the water was dominant throughout the study area except few locations. WQI showed that 55% of the pre-monsoon samples and the 47% of the post monsoon samples were classified as poor/very poor/unsuitable for drinking category. Leaching of the textile waste and their transport to the downstream was well observed during the post-monsoon season. The specific contribution of river Noyyal in the transport of the solutes to the discharge zones was proved by the hydrochemistry of the samples.

Aging Effects on the Properties of Imidazolium-, Quaternary Ammonium-, Pyridinium-, and Pyrrolidinium-Based Ionic Liquids Used in Fuel and Energy Production

Ionic liquids (ILs) are often cited for their excellent thermal stability, a key property for their use as solvents and in the chemical processing of biofuels. However, there has been little supporting data on the long-term aging effect of the temperature on these materials. Imizadolium-, quaternary ammonium-, pyridinium-, and pyrrolidnium-based ILs with the bis(trifluoromethylsulfonyl)imide and bis(perfluoroethylsulfonyl)imide anions were aged for 2520 h (15 weeks) at 200 °C in air to determine the effects of an oxidizing environment on their chemical structure and thermal stability over time. It was found that the minor changes in the cation chemistry could greatly affect the properties of the ILs over time.

In Memoriam: Max Merle Mortland (1923–2013)

Max M. Mortland, retired Distinguished Professor of Soil Science and Geology at Michigan State University, passed away peacefully on July 29, 2013, at the age of 90. Max was recognized internationally for his pioneering studies of clay-mineral-intercalation chemistry. Using infrared spectroscopy and X-ray powder diffraction as his primary instrumental methods of analysis, he elucidated the acid–base chemistry of inorganic and organic exchange cations on the interlayer surfaces of smectite clays, particularly Wyoming montmorillonite, his ‘favorite’ clay. He was the first to report electron-transfer reactions between transition-metal cations ( e.g . Cu2+) and physically adsorbed aromatic molecules ( e.g . benzene) on montmorillonite clay surfaces. These fundamental studies provided the basis for understanding the role of clay minerals in soil fertility and the development of new materials for environmental protection and clean-up based on smectitic clays. In recognition of …

GIS-based Evaluation of Water Quality Index of groundwater resources around Tuticorin coastal city, south India

Groundwater is a vital source of water for industrial, domestic and agricultural activities in Tuticorin city due to lack of surface water resources; groundwater quality and its suitability for drinking usage were evaluated. A total of 72 groundwater samples were collected from open wells and boreholes during pre and post-monsoon period. Samples were analyzed for physico-chemical properties, major cation and major anions in the laboratory using the standard methods given by the American Public Health Association. The geographic information system-based spatial distribution map of different major elements has been prepared using ArcGIS 9.2. These maps are classified as desirable, maximum permissible and the values that exceed maximum permissible limit are termed as not permissible prescribed by the WHO (2004). From the Piper plot, which gives the cation chemistry, the concentration of the alkalies (Na+ and K+) exceeds the alkaline earths (Ca2+ and Mg2+) and those of strong acids exceeds weak acids. In the case of anions, during the two periods strong acid shows dominance over weak acid and HCO3 − and Cl− have influences almost equal to Na+, which indicate the saltwater intrusion into the freshwater aquifer of the study area. A Canadian Council of Ministers for the Environment Water Quality Index (CCME WQI) map was also generated with the GIS technique to better understand the water portability over space. The categories of water quality evaluated by CCME WQI values of major part of the study area fall under fair category during PRM and good category during the POM period. The CCME WQI is a very useful and an efficient tool to summarize and to report on the monitoring data to the decision makers in order to understand the status of the groundwater quality. Finally, the study concludes that the groundwater quality is impaired by man-made activities, and proper management plan is necessary to protect valuable groundwater resources in Tuticorin city.

Heavy Metals and Major Ionic Pollution Assessment in Waters of Midstream of the River Karatoa in Bangladesh

In a quantitative assessment of water collected from the midstream of Karatoa river in Bangladesh, 31 water samples were analyzed to assess heavy metals, major ionic constituents and suitability parameters for irrigation usage. The electrical conductivity of all collected samples were within the range of 450 to 1653 ?S cm-1 indicating medium to high salinity. Total dissolved solids ranged from 247 to 789 mg L-1 and the samples were rated as fresh water (<1000 mg L-1). The anion chemistry in the Karatoa river water was dominated by HCO3- and Cl-, which contributed 66 and 31%, respectively of the total anionic mass balance. On the other hand, the cation chemistry indicated that 8 samples showed dominance sequence as Ca > Mg > Na > K, 8 samples as Ca > K > Na > Mg, 7 samples as Ca > Mg > K > Na, 6 samples as Ca > Na > K > Mg and only 2 samples as Ca > K > Mg > Na. Among the studied heavy metals (Fe, Mn, Cu, Zn, Pb, Cr and Ni), the most dominant metal was Fe and Mn. The concentration of Mn in 13 water samples exceeded the surface water quality standard (0.10 mg L-1) indicating Mn toxicity. Considering hardness, 6 water samples were graded as moderately hard while the rest 25 samples were graded as hard. As regards to permeability index, 65% of the water samples collected from the midstream of Karatoa river belongs to the unsuitable category.DOI: http://dx.doi.org/10.3329/jesnr.v5i2.14806 J. Environ. Sci. & Natural Resources, 5(2): 149-160 2012

Ultralow Thermal Conductivity in Organoclay Nanolaminates Synthesized via Simple Self-Assembly

Because interfaces impede phonon transport of thermal energy, nanostructuring can transform fully dense solids into ultralow thermal conductivity materials. Here we report a simple self-assembly approach to synthesizing organoclay nanolaminates with cross-planar thermal conductivities below 0.10 W m(-1) K(-1)-a 5-fold decrease compared to unmodified clay. These organoclays are produced via alkylammonium cation exchange with colloidally dispersed montmorillonite clay sheets followed by solvent casting. Time-domain thermoreflectance (TDTR) is used to evaluate the thermal conductivity of the organoclay nanolaminates. Variations in both organic layer thickness and cation chemistry are investigated. At these interface densities (1.0-1.5 interfaces/nm), we demonstrate that thermal conductivity is relatively independent of nanolaminate spacing. A simple series resistance model describes the behavior and gives an interfacial thermal conductance value of ≈150 MW m(-2) K(-1) for the organic/clay interface, consistent with similar organic-inorganic interfaces. The wide range of compositional substitutions and structural variations possible in these materials, make organoclays a versatile new platform for investigating the underlying physics of nanolaminate structures.

Alkaline Stability and Ion Conductivity of Polysulfone Anion Exchange Membranes (AEMs) with Different Cation Chemistries

The use of several different NMR techniques (1H, 13C, 31P, 1H decoupled phosphorus, COSY, and 1H-X (X= 13C or 31P) HMQC) were employed to elucidate the chemical structure of degraded polysulfone (PSF) anion exchange membranes (AEMs) exposed to alkaline solutions. The NMR spectra revealed degradation products perpetrated by rearrangement reactions from ylide intermediates and direct nucleophilic attack for trimethylammonium (TMA+), 1,4-dimethylpiperazinium (DMP+), 1-methylimidazolium (1M+) and trimethylphosphonium (TMP+) cations. Stevens rearrangement was the only verified rearrangement reaction for the ammonium cations. Trimethylphosphonium PSF AEMs were observed to degrade through Somelet-Hauser rearrangement. The stability experiments demonstrated that the ylide mechanisms were more prevalent at lower concentrations of alkaline solutions (e.g. 1 M Na2CO3 and 1 M KOH) when compared to higher concentrations (e.g. 6 M KOH). Also, the NMR spectra provided evidence that the introduction of alkaline stable cation sites on PSF leads to ether hydrolysis of the backbone.

Investigation of Cation Degradation in Anion Exchange Membranes Using Multi-Dimensional NMR Spectroscopy

Low temperature anion exchange polymer electrolyte membrane (AEM) based fuel cells and electrolyzers have been successfully shown to convert hydrogen and oxygen to electricity (and vice-versa) with high efficiencies and energy densities with non-precious group metals. However, a significant challenge to realizing these technologies is the poor alkaline stability of the AEMs. In this work, we present the results of our multi-faceted approach to better understand AEM degradation in alkaline media. Several two-dimensional (2D) NMR techniques were applied to comprehensively elucidate cation degradation in polysulfone-based AEMs exposed to alkaline solutions. The 2D NMR tools utilized were: a) homonuclear correlation spectroscopy (COSY), b) 1H-X (X = 13C or 31P) heteronuclear multiple quantum correlation spectroscopy (HMQC), and c) 1H-13C heteronuclear multiple bond correlation spectroscopy (HMBC). Analysis of the 2D NMR spectra enabled precise identification of the degradation products for several different cation chemistries (quaternary ammonium, imidazolium, and phosphonium types). The observation of multiple degradation products highlighted the fact that the cation groups degraded through fundamentally different mechanisms. A clear understanding of the degradation mechanism is a critical requirement in the process of selecting or designing alternate cation chemistries for alkaline resilient AEMs.

ChemInform Abstract: A Photo Touch on Amines: New Synthetic Adventures of Nitrogen Radical Cations

AbstractReview: 67 refs.

ChemInform Abstract: Cationic Tricoordinate Boron Intermediates: Borenium Chemistry from the Organic Perspective

AbstractReview: 179 refs.

A Photo Touch on Amines: New Synthetic Adventures of Nitrogen Radical Cations

Amines have been used as sacrificial electron donors to reduce photoexcited Ru(II) or Ir(III) complexes, during which they are oxidized to nitrogen radical cations. Recently, the synthetic potential of these nitrogen radical cations have caught synthetic organic chemists' attention. They have been exploited in various transformations yielding a number of elegant methods for amine synthesis. This article highlights recent developments on nitrogen radical cation chemistry under visible-light photocatalysis.

ChemInform Abstract: Heteroditopic Receptors for Ion‐Pair Recognition.

AbstractReview: 46 refs.

ChemInform Abstract: Cooperativity and the Chelate, Macrocyclic and Cryptate Effects

AbstractReview: 99 refs.

ChemInform Abstract: Recent Photo‐ and Radiation Chemical Studies of Sulfur Radical Cations

AbstractReview: 249 refs.