Dechlorination of beta-methylallyl chloride by electrogenerated [Co(I)(bipyridine)3]+: an electrochemical study in the presence of cationic surfactants

We have investigated the electrocatalytic dehalogenation of beta-methylallyl chloride (beta-mAC), widely used in the polymer industry, using [Co(I)(bpy)3]+ (where bpy=2,2'-bipyridine) electrochemically generated in situ from [Co(II)(bpy)3]2+ at a glassy carbon electrode in the presence of three different cationic surfactants in aqueous solution. Cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TDTAB), and cetylbenzyldimethylammonium chloride (CBDAC) were employed in the present investigation. The [Co(II)(bpy)3]2+-cationic surfactant systems show excellent electrocatalytic activity toward dehalogenation of beta-mAC. The dependence of the catalytic current, the corresponding potential, and the current function on the potential scan rate has been analyzed to assess the nature of the catalytic reaction. The second-order rate constant, kchem, for the reaction between the beta-mAC substrate and the electrogenerated-micelle stabilized-Co(I) complex has been calculated by a cyclic voltammetry technique. The reduction products after 3 h of bulk electrolysis have been identified by GC/MS to be one nonchloro compound (2-methyl-1,5-hexadiene (IV)) and two chloro compounds (1-chloro-2,5-dimethyl-2,5-hexadiene (V) and spiro[1.2]cylopropyl-6-chloro-5-methyl-hex-4-ene (VI)). Based on the electrochemical results and the mass spectral data, a reaction scheme involving all the reduction products has been proposed. Finally, a good correlation between the catalytic efficiency and the structural features of the surfactant molecules is demonstrated. The present study emphasizes the need for further optimization work to achieve maximum yield of nonchloro compound (IV) to employ the present [Co(II)(bpy)3]2+-cationic surfactant systems with a high catalytic efficiency as promising for possible applications.     

Facile immobilization of potassium-copper hexacyanoferrate nanoparticles using a room-temperature ionic liquid as an ionic binder and its application towards BHA determination

In this paper, a facile immobilization of copper hexacyanoferrate nanoparticles (CuHCFNP) on a paraffin wax-impregnated graphite electrode (PIGE) was carried out using the room-temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄) as an ionic binder. The characteristics of the CuHCFNP/EMIMBF₄ gel-modified electrode were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, and the modified electrode morphology was also characterized using field emission scanning electron microscopy (FESEM). The electrocatalytic behavior of butylated hydroxyl anisole (BHA) at the modified electrode has been investigated in 0.1 M KNO₃ in static and dynamic conditions. Under the optimum conditions, the oxidation peak current was proportional to the BHA concentration in the range from 1.5 to 1000 μM with a detection limit of 0.5 μM (S/N = 3). The proposed method was applied to determine BHA content in real samples with satisfactory results.

Open image in new window

Graphical abstract ?

     

Purification and biochemical characterization of two major thermophilic xylanase isoforms (T70 and T90) from xerophytic Opuntia vulgaris plant spp.

Thermostable xylanase isoforms T₇₀ and T₉₀ were purified and characterized from the xerophytic Opuntia vulgaris plant species. The enzyme was purified to homogeneity employing three consecutive steps. The purified T₇₀ and T₉₀ isoforms yielded a final specific activity 134.0 and 150.8 U mg^?1 protein, respectively. The molecular mass of these isoforms was determined to be 27 kDa. The optimum pH for the T₇₀ and T₉₀ xylanase isoforms was 5.0 and the temperature for optimal activity was 70 and 90 °C, respectively. The Km value of T₇₀ and T₉₀ enzyme isoforms was 3.49, 2.1 mg ml^?1, respectively when oat spelt xylan was used as a substrate. The T₇₀ had a Vmax of 10.4 μmol min^?1 mg^?1, and T₉₀ had a Vmax of 8.9 μmol min^?1 mg^?1, respectively. In the presence of 10 mM Co²⁺, and Mn²⁺ the activity of T₇₀ and T₉₀ isoforms increased, where as 90 % inhibition was noted with of the use 10 mM Hg²⁺, Cd²⁺, Cu²⁺, Zn²⁺ while partial inhibition was observed in the presence of Fe³⁺, Ni²⁺, Ca²⁺and Mg²⁺. The T₇₀ and T₉₀ isoforms retained nearly 50 % activity in the presence of 2.0 M urea, while use of 40 mM SDS lowered the activity nearly 38–41 %. The substrate specificity of both T₇₀ and T₉₀ isoforms showed maximum activity for oat spelt xylan. Western blot, immunodiffusion, and in vitro inhibition assays confirmed reactivity of the T₉₀ isoform with polyclonal anti-T₉₀ antibody raised in rabbit, as well as cross-reactivity of the antibody with the T₇₀ xylanase isoform.     

New rhodium(II) catalyzed synthesis of 1,4-dicarbonyl compounds from α-diazo ketones using vinyl ethers as two-carbon synthons

Rhodium(II) acetate catalyzed reactions of various α-diazo ketones, and vinyl ethers afforded γ-ketoaldehydes or 1,4-diketones in a facile manner. In this process, oxycyclopropanes are formed as intermediates, and are subsequently ring opened in the presence of the rhodium(II) acetate catalyst to furnish the corresponding 1,4-dicarbonyl compounds. The scope of this protocol has been demonstrated with the synthesis of a serotonin antagonist.     

Hypervelocity impact resistance of reinforced carbon-carbon/carbon-foam thermal protection systems

Common aero vehicles (CAVs) are aerodynamically designed, (from orbit) re-entry, un-powered military vehicles planned to be used for deployment of the desired munitions with increased accuracy and range. In one of the currently considered designs of the CAVs, their outer skin is planned to be constructed from two-ply panels. The outer play is made of a carbon-carbon composite while the inner ply is constructed from a carbon-based foam. In the present work a transient non-linear-dynamics-based analysis is carried out in order to predict the extent of damage and the probability for failure of the carbon-carbon/carbon-foam CAV panels during potential hypervelocity impact of space debris with the outer surface of the CAVs. The results obtained show that the extent of damage scales with the normal component of the momentum associated with the debris particles just before the impact. In addition, it is found that despite its relatively low strength, the carbon-foam can provide a major increase in the resistance of the CAV panels towards penetration of the hypervelocity debris particles. This finding has been linked with an attendant consolidation of the foam, the process that is capable of absorbing a substantial amount of kinetic energy carried by the debris particles.     

Effect of NiO/Ni(OH)2 nanostructures in graphene/CNT nanocomposites on their interfacial charge transport kinetics for high-performance supercapacitors

Journal of Solid State Electrochemistry - Graphene sheet/multiwall carbon nanotube (GMC) and its composites with NiO and Ni(OH)2 are synthesized by microwave-assisted technique for the application...     

Ocimum basilicum L. Methanol Extract Enhances Mitochondrial Efficiency and Decreases Adipokine Levels in Maturing Adipocytes Which Regulate Macrophage Systemic Inflammation

Excessive storage of lipids in visceral or ectopic sites stimulates adipokine production, which attracts macrophages. This process determines the pro- and anti-inflammatory response regulation in adipose tissue during obesity-associated systemic inflammation. The present study aimed to identify the composition of Ocimum basilicum L. (basil) seed extract and to determine its bio-efficacy on adipocyte thermogenesis or fatty acid oxidation and inhibition of lipid accumulation and adipokine secretion. Ocimum basilicum L. seed methanol extract (BSME) was utilized to analyze the cytotoxicity vs. control; lipid accumulation assay (oil red O and Nile red staining), adipogenesis and mitochondrial-thermogenesis-related gene expression vs. vehicle control were analyzed by PCR assay. In addition, vehicle control and BSME-treated adipocytes condition media were collected and treated with lipopolysaccharide (LPS)-induced macrophage to identify the macrophage polarization. The results shown that the active components present in BSME did not produce significant cytotoxicity in preadipocytes or macrophages in the MTT assay. Furthermore, oil red O and Nile red staining assay confirmed that 80 and 160 μg/dL concentrations of BSME effectively arrested lipid accumulation and inhibited adipocyte maturation, when compared with tea polyphenols. Gene expression level of adipocyte hyperplasia (CEBPα, PPARγ) and lipogenesis (LPL)-related genes have been significantly (p ≤ 0.05) downregulated, and mitochondrial-thermogenesis-associated genes (PPARγc1α, UCP-1, prdm16) have been significantly (p ≤ 0.001) upregulated. The BSME-treated, maturing, adipocyte-secreted proteins were detected with a decreased protein level of leptin, TNF-α, IL-6 and STAT-6, which are associated with insulin resistance and macrophage recruitment. The “LPS-stimulated macrophage” treated with “BSME-treated adipocytes condition media”, shown with significant (p ≤ 0.001) decrease in metabolic-inflammation-related proteins—such as PGE-2, MCP-1, TNF-α and NF-κB—were majorly associated with the development of foam cell formation and progression of atherosclerotic lesion. The present findings concluded that the availability of active principles in basil seed effectively inhibit adipocyte hypertrophy, macrophage polarization, and the inflammation associated with insulin resistance and thrombosis development. Ocimum basilicum L. seed may be useful as a dietary supplement to enhance fatty acid oxidation, which aids in overcoming metabolic complications.     

Effect of reaction parameters on the growth of MWCNTs using mesoporous Sb/MCM-41 by chemical vapour deposition

Mesoporous Si-MCM-41 molecular sieve was synthesized hydrothermally and different wt.% of Sb (1.0, 2.0, 3.0, 5.0, 10.0, 15.0 and 20.0) was loaded on it by wet impregnation method. The Sb/MCM-41 materials were characterized by various physico-chemical techniques such as XRD, TGA and TEM. The TEM image showed a honeycomb structure of the host material. They were used as catalytic templates for the growth of MWCNTs by CVD method with different temperatures at 700, 800, 900 and 1000 °C using acetylene as a carbon precursor. The reaction temperature was optimized for the better formation of MWCNTs and they were purified and then characterized by XRD, SEM, HR-TEM and Raman spectroscopy techniques. The formation of MWCNTs with diameter in the range of 4−6 nm was observed from HR-TEM. The good thermal stability and high productivity of catalyst observed in this study revealed that the 2 wt.% Sb loaded MCM-41 could be a promising support for the catalytic synthesis of MWCNTs at 800 °C by CVD method.     

Fabrication of multiwalled carbon nanotubes in the channels of iron loaded three dimensional mesoporous material by catalytic chemical vapour deposition technique

The growth of multiwalled carbon nanotubes (MWNTs) was successfully achieved in the channels of three dimensional (3D) iron loaded mesoporous matrices (KIT-6) by employing catalytic chemical vapour deposition (CCVD) technique. The synthesised MWNTs, which were characterised by SEM, TEM and Raman spectroscopy, consist of thick graphene layers of about 10 nm composed of 29 graphene sheets with inner and outer diameter of ∼17 nm and ∼37 nm, respectively. The Raman spectrum showed the formation of well-graphitised MWNTs with significantly higher I_G/I_D ratio of 1.47 compared to commercial MWNTs. Comparatively, 2 wt% Fe loaded KIT-6 material produced a better yield of 91%, which is also highest compared with the report of MWNTs synthesis using mesoporous materials reported so far.