Search Results (52)

In 2019, carbamates derived from 3-hydroxypyridine were classified as nerve agents and subsequently included in the Annex on Chemicals by the Conference of the States Parties. Herein, we describe the preparation of a structural simulant of this class of compounds, 10-hydroxy-N,N-dimethyl-N-((3-(tosyloxy)pyridin-2-yl)methyl)decan-1-aminium bromide. The compound was synthesized via tosylation of 2-((N,N-dimethylamino)methyl)pyridin-3-ol with tosyl chloride in the presence of sodium hydride, followed by alkylation of the resulting ((N,N-dimethylamino)methyl)pyridin-3-yl 4-methylbenzenesulfonate with 10-bromodecan-1-ol. Full article

A technique has been proposed and experimentally tested for measuring the hydrogen concentration in an inert atmosphere within a closed system. This method utilizes a metal-oxide-semiconductor field-effect capacity-type (MOSFEC) sensor under harsh conditions such as exposure to inert gases, pressure fluctuations, and varying temperatures. The measurement is performed during the thermal decomposition of metal hydrides in a liquid sodium environment. The developed measurement technique for determining hydrogen concentration released from metal hydride samples in a system with a closed gas path is cost-effective compared to standardized, resource-intensive open-volume flow measurement methods. The use of the developed MOSFEC sensor technique allows for rapid and efficient investigation of the in situ real-time dynamics of gas release from various metal hydride materials differing in their hydrogen content within a small closed volume. Additionally, this approach enables precise determination of the specific gas release temperatures. Full article

Magnesium hydride (MgH₂) has attracted considerable interest due to a number of favourable characteristics for hydrogen production via hydrolysis. In this study, MgH₂-NaH composites with varying composition ratios were prepared by ball milling for different durations. The hydrogen production performances and enhancement mechanisms were subjected to meticulous investigation. The results revealed that the hydrogen production rate and kinetic properties of the composites were significantly improved with the rise in NaH content. For the MgH₂-10 wt% NaH composites, the hydrogen production rate exhibited an initial increase followed by a subsequent decrease with the prolongation of ball milling. It is noteworthy that the hydrolysis of the composites in deionised water exhibited a significant improvement in reaction kinetics even after a mere 1 h of ball milling, releasing 1119 mL g⁻¹ of hydrogen in 30 s, with a conversion rate of 69.2%. The highest hydrolysis hydrogen generation rate of the 10 h milled MgH₂-10 wt% NaH composite in deionised water at 30 °C was 1360 mL g⁻¹, with a hydrogen conversion rate of 83.7% and a hydrolysis activation energy of 17.79 kJ mol⁻¹. The notable improvement in the hydrolysis performance of the MgH₂-NaH composite is attributed to the rapid generation of high temperatures at the interface, resulting from the exothermic reaction of sodium hydride hydrolysis. Full article

The growing population and increasingly competitive economic climate have increased the demand for alternative fuel sources, with hydrogen being one of the more viable options. Many metal hydrides, including sodium borohydride, are capable of releasing hydrogen stored within chemical bonds when reacted with water, but the rate of generation is slow and therefore necessitates a catalyst. Silver nanoparticles, which were chosen due to their known catalytic activity, were synthesized from sodium citrate and were embedded in mesoporous carbon to form a nano-composite catalyst (Ag-MCM). This composite was characterized via Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Scanning Electron Microscopy/Energy-Dispersive X-ray Spectroscopy (SEM/EDS). Catalytic testing showed that the catalytic activity for the Ag-MCM catalyst increased with increasing NaBH₄ concentration, low pH, and high temperatures. The Ag-MCM catalyst resulted in the activation energy at 15.6 kJ mol⁻¹, making it one of the lowest seen activation energies for inorganic catalysts. Lastly, the Ag-MCM catalysts showed stability, producing, on average, 20.0 mL per trial for five consecutive trials. This catalytic ability along with the cheap, carbon-based backbone that is made from readily available corn starch, makes it a promising catalyst for the hydrolysis of NaBH₄. Full article

By reacting nitrilium derivative of the closo-dodecaborate anion, Bu₄N[B₁₂H₁₁N≡CR] (where R = Me, Et, nPr, iPr, p-tolyl), with lithium aluminum hydride (LiAlH₄), N-alkylammonium derivatives of the closo-dodecaborate anion, and Bu₄N[B₁₂H₁₁NH₂CH₂R], were obtained. The reduction reaction procedure was optimized, achieving yields close to quantitative (90–95%). The structure of the compound Bu₄N[B₁₂H₁₁NH₂CH₂CH₃] was determined using X-ray structural analysis. It was found that substituting lithium aluminum hydride (LiAlH₄) with sodium borohydride (NaBH₄) leads to the same products but only upon heating, while the reaction with LiAlH₄ proceeds at room temperature. Full article

This work focuses on the recovery of rare earth elements (REEs = La, Ce, Nd, Pr) from spent nickel–metal hydride batteries by hydrometallurgical processing. The REEs were precipitated in the form of sodium-lanthanide double sulfate salts by adding Na₂SO₄ to a leach liquor prepared from industrially processed spent batteries. The objectives were to better understand the parameters driving the purity of the product and to identify the phases involved, as well as their crystallographic structure. The methodology included experiments performed in a 2 L reactor, thermodynamic calculations and product characterization. We confirmed that high REE precipitation yields (>95%) can be achieved under a wide range of hydrodynamic conditions. Furthermore, we demonstrated and quantified how appropriately washing the product allows for a significant reduction in nickel losses while maintaining control over REE product purity. Finally, using X-ray Diffraction analyses, it was established that REEs form a solid solution with a chemical formula (Na_0.9K_0.1)(La_0.65Ce_0.24Pr_0.04Nd_0.07)(SO₄)₂·H₂O, which has not been reported so far. Full article

Back-scattered electron imaging and X-ray elemental mapping were combined in a tabletop scanning electron microscope (SEM) to investigate cross-sections of three AA-type (mignon) nickel–metal hydride (NiMH) batteries from different manufacturers. All batteries underwent 500–800 charge/discharge cycles and reached their end of lifetime after several years as they could no longer hold any significant electric charge (less than 20% of nominal charge capacity), but none showed any short-circuiting. The types of degradation observed in this field study included electrode swelling, metallic nickel formation and carbon incorporation into pores in the positive electrodes and, in the negative electrodes, metal alloy segregation of different elements such as nickel, lanthanum and, in one case, sodium, as well as grain break-up and pore formation. All these phenomena could readily be observed at rather small magnifications. This will be important for the improvement of NiMH batteries, for which new generations with nominally slightly increased charge capacities are being marketed all the time. Full article

This paper considers the features of determining the total tin content in waters with different salinity. Direct ICP-spectrometric analysis of sea waters with a salinity of more than 6‰ significantly reduced the analytical signal of tin by 70% (ICP-MS) and 30% (ICP-OES). The matrix effect of macrocomponents was eliminated by generating hydrides using 0.50 M sodium borohydride and 0.10 M hydrochloric acid. The effect of transition metals on the formation of tin hydrides was eliminated by applying L-cysteine at a concentration of 0.75 g/L. The total analyte concentrations, considering the content of organotin compounds, were determined after microwave digestion of sample with oxidizing mixtures based on nitric acid. The generation of hydrides with the ICP-spectrometric determination of tin leveled the influence of the sea water matrix and reduced its detection limit from 0.50 up to 0.05 µg/L for all digestion schemes. The developed analysis scheme made it possible to determine the total content of inorganic and organic forms of tin in sea waters. The total content of tin was determined in the waters of the Azov and Black seas at the levels of 0.17 and 0.24 µg/L, respectively. Full article

A new alkyne functionalized pterin derivative was synthesized through a reaction of 7-chloropterin with propargyl alcohol in the presence of sodium hydride. The purity and chemical structure of the compound was validated by NMR (¹H, ¹³C) spectroscopy, Mass (APCI source) spectrometry, elemental analysis, and X-ray crystallography. The title compound may be further functionalized by exploiting the yne moiety, for instance, using click chemistry. The novel pterin derivative, most notably, in contrast to typical pterin behavior, is now soluble or even well soluble in almost any solvent except water. Full article

The construction of duocarmycin-like compounds is often associated with lengthy synthetic routes. Presented herein is the development of a short and convenient synthesis of a type of duocarmycin prodrug. The 1,2,3,6-tetrahydropyrrolo[3,2-e]indole-containing core is here constructed from commercially available Boc-5-bromoindole in four steps and 23% overall yield, utilizing a Buchwald–Hartwig amination followed by a sodium hydride-induced regioselective bromination. In addition, protocols for selective mono- and di-halogenations of positions 3 and 4 were also developed, which could be useful for further exploration of this scaffold. Full article

Efficient ¹³C hyperpolarization of ketoisocaproate is demonstrated in natural isotopic abundance and [1-¹³C]enriched forms via SABRE-SHEATH (Signal Amplification By Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei). Parahydrogen, as the source of nuclear spin order, and ketoisocaproate undergo simultaneous chemical exchange with an Ir-IMes-based hexacoordinate complex in CD₃OD. SABRE-SHEATH enables spontaneous polarization transfer from parahydrogen-derived hydrides to the ¹³C nucleus of transiently bound ketoisocaproate. ¹³C polarization values of up to 18% are achieved at the 1-¹³C site in 1 min in the liquid state at 30 mM substrate concentration. The efficient polarization build-up becomes possible due to favorable relaxation dynamics. Specifically, the exponential build-up time constant (14.3 ± 0.6 s) is substantially lower than the corresponding polarization decay time constant (22.8 ± 1.2 s) at the optimum polarization transfer field (0.4 microtesla) and temperature (10 °C). The experiments with natural abundance ketoisocaproate revealed polarization level on the ¹³C-2 site of less than 1%—i.e., one order of magnitude lower than that of the 1-¹³C site—which is only partially due to more-efficient relaxation dynamics in sub-microtesla fields. We rationalize the overall much lower ¹³C-2 polarization efficiency in part by less favorable catalyst-binding dynamics of the C-2 site. Pilot SABRE experiments at pH 4.0 (acidified sample) versus pH 6.1 (unaltered sodium [1-¹³C]ketoisocaproate) reveal substantial modulation of SABRE-SHEATH processes by pH, warranting future systematic pH titration studies of ketoisocaproate, as well as other structurally similar ketocarboxylate motifs including pyruvate and alpha-ketoglutarate, with the overarching goal of maximizing ¹³C polarization levels in these potent molecular probes. Finally, we also report on the pilot post-mortem use of HP [1-¹³C]ketoisocaproate in a euthanized mouse, demonstrating that SABRE-hyperpolarized ¹³C contrast agents hold promise for future metabolic studies. Full article

Benzylic alcohols are among the most important intermediates in organic synthesis. Recently, the use of abundant metals has attracted significant attention due to the issues with the scarcity of platinum group metals. Herein, we report a sequential method for the synthesis of benzylic alcohols by a merger of iron catalyzed cross-coupling and highly chemoselective reduction of benzamides promoted by sodium dispersion in the presence of alcoholic donors. The method has been further extended to the synthesis of deuterated benzylic alcohols. The iron-catalyzed Kumada cross-coupling exploits the high stability of benzamide bonds, enabling challenging C(sp²)–C(sp³) cross-coupling with alkyl Grignard reagents that are prone to dimerization and β-hydride elimination. The subsequent sodium dispersion promoted reduction of carboxamides proceeds with full chemoselectivity for the C–N bond cleavage of the carbinolamine intermediate. The method provides access to valuable benzylic alcohols, including deuterium-labelled benzylic alcohols, which are widely used as synthetic intermediates and pharmacokinetic probes in organic synthesis and medicinal chemistry. The combination of two benign metals by complementary reaction mechanisms enables to exploit underexplored avenues for organic synthesis. Full article

Limonin is a natural compound which is rich in the fruit of various plants of the Rutaceae family and demonstrated to have a wide range of biological activities. In this work, seven limonin derivatives were successfully synthesized by hydrogenation of limonin, using different reducing agents (sodium cyanoborohydride, lithium aluminum hydride, and sodium borohydride). The chemical structure of the seven derivatives was characterized and identified by a series of techniques, including HR-ESI-MS, 1H-NMR, 13C-NMR, 2D-NMR, and IR. Among the seven limonin derivatives, six limonin derivatives were found to be new compounds which have not been previously reported. Then, the anti-inflammatory activities of the seven synthesized limonin derivatives, as well as the anti-inflammatory activities of eight known natural limonins, were evaluated and compared. Natural limonins, 30-O-Acetylhainangranatumin E and Xylogranatin A, presented significantly better anti-inflammatory activity. Xylogranatin A could inhibit LPS-induced RAW264.7 cell inflammatory factors, with a 90.0% inhibition ratio of TNF-α and 63.77% inhibition ratio of NO release in LPS-induced BV2 cells at 10 μM. Other natural limonins showed poor anti-inflammatory activity. In comparison, all the synthetic limonin derivatives showed decent anti-inflammatory activities, with the highest inhibition ratio of TNF-α of 37.8% and inhibition ratio of NO release of 12.5% in LPS-induced BV2 cells at 10 μM. Full article

Metal hydrides such as MgH₂ and NaBH₄ are among the materials for with the highest potential solid-state hydrogen storage. However, unlike gas and liquid storage, a dehydrogenation process has to be done prior to hydrogen utilization. In this context, the hydrolysis method is one of the possible methods to extract or generate hydrogen from the materials. However, problems like the MgH₂ passivation layer, high cost and sluggish self-hydrolysis of NaBH₄ are the known limiting factors for this process, but they can be overcome with the help of catalysts. In this works, selected studies have been reviewed on the performance of catalysts like chloride, oxide, fluoride, platinum, ruthenium, cobalt and nickel-based on the MgH₂ and NaBH₄ system. These studies show a significant enhancement in the amount of hydrogen released as compared to the hydrolysis of the pure MgH₂ and NaBH₄. Therefore, the addition of catalysts is proven as one of the options in improving hydrogen generation via the hydrolysis of MgH₂ and NaBH₄. Full article

We report on the design, synthesis, and characterization of the first silver hydride clusters solely protected and stabilized by dithiophosphonate ligands and their application for the in situ generation of silver nanoparticles towards the catalytic reduction of 4-nitrophenol in an aqueous system. The synthesis of the silver monohydride cluster involves the incorporation of an interstitial hydride using sodium borohydride. Poly-nuclear magnetic resonance and mass spectrometry were used to establish the structural properties. The structural properties were then confirmed with a single-crystal X-ray diffraction analysis, which showed a distorted tetracapped tetrahedron core with one hydride ion encapsulated within the core of the silver framework. Additionally, the synthesized heptanuclear silver hydride was utilized as a precursor for the in situ generation of silver nanoparticles, which simultaneously catalyzed the reduction of 4-nitrophenol. The mechanism of the catalytic activity was investigated by first synthesizing AgNPs, which was subsequently used as a catalyst. The kinetic study showed that the pseudo-first constant obtained using the cluster (2.43 × 10⁻² s⁻¹) was higher than that obtained using the synthesized AgNPs (2.43 × 10⁻² s⁻¹). This indicated that the silver monohydride cluster was more active owing to the release of the encapsulated hydride ion and greater reaction surface prior to aggregation. Full article