Concurrent Reactions Research Articles

SPECIFIC NATURE OF ACID-BASE INTERACTION OF OCTA(4-TERT-BUTYLPHENYL)TETRAPYRAZINOPORPHYRAZINE WITH ORGANIC PROTON-ACCEPTOR MOLECULES IN BENZENE

The reaction of acid-base interaction of octa(4-tert-butylphenyl)tetrapyrazinophosphyrazine with pyridine, 2-methylpyridine, morhpoline, pipyridine, n-butylamine, tert-butylamine, diethylamine, triethylamine and dimethylsulfoxide in benzene was investigated. It is shown that the researched porphyrazine forms kinetically stable proton transfer complexes with pyridine, 2-methylpyridine, morpholine and dimethylsulfoxide. In benzene-base system an acid-base equilibrium between the molecular form of octa(4-tert-butylphenyl)tetrapyrazinoporphyrazine and its proton transfer complex was established. The interaction of substituted tetrapyrazinoporphyrazine with morpholine in benzene was revealed to be a kinetically controllable process which occurs with low reaction rate and high values of activation energy. Such values are not inherent to most of relatively simple liquid-phase acid-base systems. The kinetic equation of the process was found, and, based on the spectral changes accompanying the reaction, a cheme of two-stage process of proton transfer of NH-groups of octa(4-tert-butylphenyl)tetrapyrazinoporphyrazine to morpholine in benzene was proposed. A possible structure of proton transfer complex of octa(4-tert-butylphenyl)tetrapyrazinoporphyrazine with organic bases is shown. In these complexes the inner hydrogen atoms of the cycle, bonded with base molecules, lie under and above the plane of the molecule, and the proton transfer from acid to base is limited either by the H-complex or the ion-ion associates constituting an H-bonded ion pair. Depending on the proton accepting tendency of the base, the acid-base equilibrium can shift towards or away from the more or less polarized structure. It was revealed that in benzene - n-butylamine (tri-butylamine, diethylamine, triethylamine, pipyridine) system the acid-base interaction involving octa(4- tert-butylphenyl)tetrapyrazinoporphyrazine occurs incredibly fast, with rates not measurable by standard spectrophotography methods. The forming proton transfer complexes are highly labile due to concurrent proton reaction occurring, leading to the formation of dianion form of octa(4- tert-butylphenyl)tetrapyrazinoporphyrazine. This form undergoes spontaneous dissolution into low-molecular colorless products due to the lack of compensation of excess charge in the macrocycle.

Electrooxidation of urea and creatinine on nickel foam-based electrocatalysts

Electrooxidation of urea and creatinine is desirable for wastewater remediation and portable dialysis to remove the two solutes from aqueous waste streams. Urine concentrations of urea (330 mM) and creatinine (18 mM) are relevant for wastewater remediation, while portable dialysis must be able to remove blood serum concentrations of urea (10 mM) and creatinine (0.18 mM) from dialysate. Three nickel foam-based electrocatalysts (clean Ni foam, Ni hydroxide, and Ni hydroxide doped with 1 mol% iron) were examined as substrates for the simultaneous electrooxidation of urea and creatinine. Electrodes were hydrothermally fabricated and characterized by loading, scanning electron microscopy, and elemental mapping. Cyclic voltammetry and chronoamperometry were used to electrochemically evaluate the three catalysts. All electrochemical experiments were performed at room temperature and pH 14. The results indicate that creatinine in urea solutions suppresses the oxidation current relative to urea-only solutions on Ni foam and Ni hydroxide catalysts. On iron-doped Ni hydroxide, an enhanced oxidation current occurs in cyclic voltammetry of creatinine/urea solutions, with the effect greater for dialysate-relevant concentrations. In chronoamperometry measurements, a slight decrease in oxidation current is observed for urea/creatinine solutions as compared with urea alone. This behavior is attributed to concurrent reactions of urea and creatinine subject to site blocking by adsorbed creatinine fragments that becomes evident at long timescales.

Pru p 3 Sublingual Immunotherapy in Patients with Lipid Transfer Protein Syndrome: Is It Worth?

Background: Lipid transfer proteins (LTPs) syndrome is an important cause of multiple plant food allergy in the Mediterranean area. The effectiveness of sublingual immunotherapy (SLIT) with the LTP Pru p 3 extract has been little investigated in the real-world setting. This study aimed to investigate the outcome of Pru p 3 SLIT in real-life patients with LTP syndrome with/without concurrent reactions to peanut and/or nuts. Methods: This was a prospective real-life study including all patients diagnosed with LTP allergy and treated with Pru p 3 SLIT between 2011 and 2018 in a tertiary hospital in Spain. Patients underwent open oral food challenge (OFC) tests for unpeeled peach and nuts/peanuts 1 year after the treatment started to assess food tolerance. A control group of patients diagnosed with LTP allergy who refused treatment with immunotherapy were included. Severity of symptoms and diet avoidance was recorded in both groups. Results: Twenty-nine patients with a median age of 24.7 years (range 5.5–43.1) were included: 100% were allergic to fruit; 72%, to peanut and/or nuts; 19 had a history of severe systemic reactions. Seven patients discontinued therapy; 3 (10%), due to adverse events. One year after SLIT start, 16 (73%) patients had negative OFC to peach; 95%, after 2 years; 69% had negative OFC to nuts/peanuts. The control group included 13 patients: 53.8% experienced reactions with new foods; severity of symptoms increased significantly (p < 0.001), and diet restrictions were maintained in this group. Conclusions: SLIT with Pru p 3 shows a good safety profile, and avoid dietary restrictions in patients with LTP syndrome treated in the real-life setting.

How and Why to Investigate Multicomponent Reactions Mechanisms? A Critical Review.

We review the most innovative efforts and greatest challenges faced when elucidating multicomponent reactions (MCRs) mechanisms. When compared to traditional reactions, the often two or more concurrent reactions pathways and the greater number of possible intermediates in MCRs turn their mechanistic investigation both a harder and trickier task. The common approaches used to investigate reaction mechanisms are often unable to clarify MCRs mechanisms; hence few but clever approaches are currently used to determine these mechanisms and to depict their key transformations. Their complexity has required most innovative approaches and the use of a number of unique techniques that have shed light over the favored pathway selected from the myriad of alternatives theoretically available for MCRs. This review focuses on the most successful efforts applied by a few leading groups to perform these puzzlingly investigations.

Hydrogen peroxide formation in water during the VUV/UV irradiation process: Impacts and mechanisms of selected anions

Understanding the formation and transformation of radicals generated by a low pressure mercury lamp emitting both 254 nm ultraviolet (UV254) and 185 nm vacuum UV (VUV185) is currently challenging due to the complexity of concurrent redox reactions occurring in this complex system. Because hydrogen peroxide (H2O2) is a common product of both oxidizing and reducing radicals generated during the VUV irradiation process, monitoring the variations in H2O2 levels can help us better understand the presence and relative dominance of different radicals. In this study, we systematically evaluated the effects of several selected anions on the formation of H2O2 under a variety of pH and dissolved oxygen (DO) conditions. Results show that although addition of these anions inhibited the formation of H2O2, their H2O2-inhibition mechanisms are markedly different. At low concentrations (≤1.0 mg/L), chloride reduced the generation of H2O2 primarily by consuming hydroxyl radicals (•OH); however, in high concentrations (11.0 mg/L), its light-screening effect was dominant. In comparison, the presence of bromide (≤1.0 mg/L) inhibited H2O2 formation mainly by reacting rapidly with both •OH and H2O2. Carbonate and phosphorous species exerted influence mainly by consuming •OH. Along with irradiation, increasing pH significantly decreased H2O2 levels, confirming that H2O2 was formed mainly by •OH. In contrast, raising DO did not raise H2O2 maximum yields, confirming that reducing radicals like aqueous electrons (e-aq) and hydrogen atoms (•H) are not the key precursors of H2O2 in this process. Mathematically, the evolutions of H2O2 can be reliably modeled (R2 ≥ 0.80) using a kinetics model incorporating H2O2 formation and decomposition kinetics. The results of this study may contribute to better understanding the use of VUV technology in water/wastewater treatment.

Ultrathin Porous Carbon Nitride Bundles with an Adjustable Energy Band Structure toward Simultaneous Solar Photocatalytic Water Splitting and Selective Phenylcarbinol Oxidation

AbstractActiniae‐like carbon nitride (ACN) bundles were synthesized by the pyrolysis of an asymmetric supramolecular precursor prepared from L‐arginine (L‐Arg) and melamine. ACN has adjustable band gaps (2.25 eV–2.75 eV) and hollow microtubes with ultrathin pore walls, which enrich reaction sites, improve visible‐light absorption and enhance charge separation. In the presence of phenylcarbinol, ACN exhibited excellent water‐splitting ability (95.3 μmol h−1) and in the meanwhile phenylcarbinol was selectively oxidized to benzaldehyde (conversion of 90.9 %, selectivity of 99.7 %) under solar irradiation. For the concurrent reactions, 2D isotope labeling, separation, and detection were conducted to confirm that the proton source of released hydrogen is water. The mechanism of water splitting and phenylcarbinol oxidation was also investigated.

Allergens in Hand, Foot, and Hand-Foot Eczema: An Intercomparison by Patch Testing.

Background:Hand eczema (HE), foot eczema (FE), and hand–foot eczema (HFE) manifest on exposure to various agents in day-to-day life or in occupations or both.Objectives:The objectives of this study were to identify pattern of allergens causing HE, FE, and HFE and to identify multiple and concurrent contact allergies.Materials and Methods:A study was conducted from October 2013 to August 2015 which included 190 patients. Patch test was performed for 78.94% of patients (n = 150). The statistical tests used were descriptive, Cramer's V, and Chi-square tests. Results:The most commonly affected group was HFE (55.8%) followed by HE (22.1%) and FE (22.1%). Allergens showed positivity either singly 56.3% (n = 67) or in combination 43.69% (n = 52). Nickel (41.79%) was the most common allergen in all the three groups followed by potassium dichromate. Late reactions (after day 7) were observed in 17.64% of patients (n = 21). Nickel was observed in 42.85% (n = 9) and paraphenylenediamine was observed in 28.57% of patients (n = 6) with P values of <0.001 and 0.050, respectively. Multiple contact allergies were seen in 44% of patients (n = 52). Concurrent reactions (55.8% [n = 29]), polysensitization (34.6% [n = 18]), and mixed reactions (9.6% [n = 5]) (P value of <0.001) were observed.Conclusion:Significant multiple contact allergies including concurrent reactions with nickel sulfate, potassium dichromate, cobalt chloride, and polysensitization were observed. No significant differences in allergen pattern were observed in HE, FE, and HFE.Recommendation:Day 7 reading is recommended in HFE.

A glimpse into the black box of celiac disease complications: a case report with a rare presentation.

The purpose of this article is to report a case of celiac disease in a child with uncommon presentation and severe complications, and briefly review recent literature regarding celiac disease complications in children. We describe a case report of celiac disease in a child (to our knowledge, this is the first to be reported in its unique presentation in the Russian Federation) and precisely review its presenting complications with the exiting works of literature. Many cases of celiac disease in children who are not diagnosed and treated properly suffer from a plethora of complications due to malabsorption and concurrent autoimmune reactions that affect mainly but are not limited to the endocrine system. Complications of celiac disease in children should always be suspected, and evidence-based follow-up recommendations should be introduced as soon as possible because the burden of celiac disease complications in children is remarkable.

Dimethyl isosorbide via organocatalyst N-methyl pyrrolidine: scaling up, purification and concurrent reaction pathways

High-yielding methylation of isosorbide via DMC chemistry promoted by N-methyl pyrrolidine is herein reported. This study addresses: DMI purification, scale-up tests, insights on the catalyst role and on the reaction pathways leading to DMI.

Tunable Electronic Metal–Support Interactions on Ceria-Supported Noble-Metal Nanocatalysts in Controlling the Low-Temperature CO Oxidation Activity

A fundamental study on the metal-support interactions of supported metal catalysts is of great importance for developing heterogeneous catalysts with high performance, is still attracting and challenging in many heterogeneous catalytic reactions. In this work, we report the catalytic performances of CeO2-supported noble-metal catalysts among single atoms, subnanoclusters (∼1 nm), and nanoparticles (2.2-2.7 nm) upon low-temperature CO oxidation reaction between 50 and 250 °C. The subnanoclusters and nanoparticles of Ru, Rh, and Ir showed much higher activities than those of the single atoms, while a Pd single-atom catalyst was more active than Pd subnanoclusters and nanoparticles. According to the results of multiple ex situ and in situ characterizations, the much different activities of Ru, Rh, Ir, and Pd were derived from the alterable electronic metal-support interactions (EMSI), which determine the concurrent reaction pathway including the famous Mars van Krevelen mechanism and carbonate-intermediate route on the most active metal sites of Mδ+ (0 < δ < 1) for Ru, Rh, and Ir and Pd2+ for Pd. Also, the moderate EMSI of CeO2-supported Rh subnanoclusters furthest benefited activation of the adsorbed CO molecule and ensured it the highest activity among CeO2-supported Ru, Rh, and Ir catalysts with similar metal deposit sizes.

Food antigen-specific IgE in dogs with suspected food hypersensitivity

Knowledge of cross-reactions in food-sensitive dogs will influence the choice of elimination diets and the long-term management of those patients. The objective of this study was to evaluate food allergen-specific IgE tests of suspected allergic dogs for concurrent positive reactions as possible evidence for cross reactions between allergens. Results of serum IgE tests from 760 suspected allergic dogs submitted to 2 laboratories were evaluated statistically. After the tested allergens were grouped by their phylogenetic relationship, odds ratios as well as a sensitivity analysis of the odds ratios were performed to evaluate if concurrent positive IgE results to 2 allergens occurred more often than expected. Within related allergen pairs 27% (laboratory 1) and 72% (laboratory 2) of the pairs could be considered as associated. For the unrelated allergen pairs only 6.8% and 10.6% of the analyzed pairs were considered associated respectively. Strong correlations were shown in the group of ruminant allergens, especially beef and lamb, and grain allergens. High rates of concurrent reactions were also detected in the poultry group, especially between chicken and duck, as well as between pork and ruminant allergens, and soy and grain allergens. As our results showed not only correlations within related but also between non-related allergens, the possible relevance of carbohydrate moieties as well as panallergens for canine hypersensitivities warrants further study. Further investigations are necessary to distinguish co-sensitization from cross-reactions and determine the clinical relevance of food-specific IgE reactivity. Due to possible cross reactivity related allergens, especially beef and lamb as well as grain allergens, should not be used for an elimination diet to avoid false results.

A Detailed Kinetico-Mechanistic Investigation on the Palladium C-H Bond Activation in Azobenzenes and Their Monopalladated Derivatives.

Palladium C-H bond activation in azobenzenes with R1 and R2 at para positions of the phenyl rings (R1 = NMe2, R2 = H (L1); R1 = NMe2, R2 = Cl (L2); R1 = NMe2, R2 = I (L3); R1 = NMe2, R2 = NO2 (L4); R1 = H, R2 = H (L5)) and their monopalladated derivatives, using cis-[PdCl2(DMF)2], has been studied in detail by in situ 1H NMR spectroscopy in N,N-dimethylformamide-d7 (DMF-d7) at room temperature; the same processes have been monitored in parallel via time-resolved UV-vis spectroscopy in DMF at different temperatures and pressures. The final goal was to achieve, from a kinetico-mechanistic perspective, a complete insight into previously reported reactivity results. The results suggest the operation of an electrophilic concerted metalation-deprotonation mechanism for both the mono- and dipalladation reactions, occurring from the coordination compound and the monopalladated intermediates, respectively. The process involves deprotonation of the C-H bond assisted by the presence of a coordinated DMF molecule, which acts as a base. For the first time, NMR monitoring provides a direct evidence of all the intermediate stages: that is, (i) coordination of the azo ligand to the PdII center, (ii) formation of the monopalladated species, and (iii) coordination of the monopalladated species to another PdII unit, which finally result in the (iv) formation of the dipalladated product. All of these species have been identified as intermediates in the dipalladation of azobenzenes, evidenced also by UV-vis spectroscopy time-resolved monitoring. The data also confirm that the cyclopalladation of asymmetrically substituted azobenzenes occurs by two concurrent reaction paths. In order to identify the species observed by NMR and by UV-vis spectroscopy, the final products, intermediates, and the PdII precursor have been prepared and characterized by X-ray diffraction and IR and NMR spectroscopy. DFT calculations have also been used in order to explain the isomerism observed for the isolated complexes, as well to assign their NMR and IR spectra.

Prevalence, concomitant reactions, and factors associated with fragrance allergy in Thailand.

Fragrances are the most common cause of cosmetic contact allergy. Up-to-date information on contact allergy frequencies and relevance aids primary and secondary preventive measures. To determine the prevalence, associated factors, and concomitant reactions in fragrance allergy among Thais. This retrospective study collected data from 2012 to 2019. The patient characteristics of fragrance and nonfragrance allergy groups were compared. Concurrent positive reactions to fragrance allergens (fragrance mix [FM] I, FM II, Myroxylon pereirae resin and hydroxyisohexyl 3-cyclohexene carboxaldehyde) and other baseline-series allergens were analysed. Of 1032 patients, 175 (17.0%) had fragrance allergy, with 57.7% of clinical relevance. FM I showed the highest prevalence (9.4%). The associated factors were being elderly, lesions on the extremities, metal allergy history, and long dermatitis duration. Contact allergies to epoxy resin and Compositae plants were significantly associated with fragrance allergy with an odds ratio of 5.95 (95% confidence interval [CI]: 5.21-6.80) and an odds ratio of 4.42 (95% CI: 1.58-12.36), respectively. No significant associations between colophonium (previously proposed as a fragrance marker) and fragrance allergens were found. The prevalence of fragrance contact allergy remains high and should be considered in old patients presenting with long-standing eczema on the extremities. Unlike reports from other countries, varied, significant, concomitant reactions were observed.

Carbon Nitride Quantum Dots Enhancing the Anodic Electrochemiluminescence of Ruthenium(II) Tris(2,2'-bipyridyl) via Inhibiting the Oxygen Evolution Reaction.

Although electrochemiluminescence (ECL) has been developed significantly in the past few decades, ECL efficiency in aqueous solutions remains quite low. Determination of the energy losses and development of new ECL-enhancing strategies are still of great value. In this work, we discovered a detrimental nonradiation relaxation pathway by a concurrent oxygen evolution reaction (OER) process in a well-known ruthenium(II) tris(2,2'-bipyridyl) (Ru(bpy)32+) aqueous ECL system due to similar surface-sensitive characteristics, and for the first time, a chemical strategy was developed by which carbon nitride quantum dots (CNQDs) could inhibit the surface OER process, alleviate the energy losses by nonradiation relaxation, and enhance the anodic ECL of Ru(bpy)32+. In the Ru(bpy)32+/CNQD system, CNQDs could enhance the anodic ECL of Ru(bpy)32+ in a nitrogen stream (10-fold) and ambient air (161-fold). The luminous and nitrogen-rich CNQDs were also confirmed not to serve as ECL luminophores, anodic coreactants, or donor/acceptors in ECL. The coreactant-free Ru(bpy)32+/CNQD system possesses several advantages over the common coreactant ECL system, such as low dosage (100 μg/mL CNQDs), favorable regeneration capacity, etc. As an example, ECL on-off detection of dopamine utilizing the Ru(bpy)32+/CNQD system was also developed to show prospects in ECL sensing. Besides, CNQDs were introduced into the classical Ru(bpy)32+/C2O42- coreactant ECL system, leading to suppressed OER and improved ECL signal. Overall, the proposed new ECL-enhancing strategy is promising for applicable ECL sensing, could be extended to other ECL luminophores with high oxidation potential, and enables an in-depth understanding of the ECL process and mechanism.

Atomic scale mechanism of clay minerals dissolution revealed by ab initio simulations

Large-scale ab initio Meta-Dynamics simulations were applied to elucidate the molecular mechanism and reaction free energies of pyrophyllite dissolution at the (1 1 0) edge surface in pure water at close to neutral pH under far from equilibrium conditions. The simulation setup allows realistic representation of the clay mineral surface and explicit consideration of solvent dynamics at finite temperature. The simulation reveals that dissolution of a single tetrahedral or an octahedral unit from the clay mineral edge is a complex multi-step process with several reaction intermediates. Typically, each reaction step changes denticity of the reacting site in a step-by-step manner and leads, eventually, to the leaching of ions forming octahedral and tetrahedral sheets of the phyllosilicate. The solvent rearrangement and the proton transfer reactions in the first and the second coordination shell of the dissolving unit play a critical role in the stabilization of reaction intermediates and the net progress of the dissolution reactions. The overall reaction mechanism can be rationalized as sequence of concurrent and reversible elementary reaction events, which are:(1)the nucleophilic attack of H2O molecules or OH groups on the dissolving surface site.(2)ligand exchange reactions in the first coordination shell of the reacting sites leading to changes of its conformation and denticity at the mineral surface.(3)collective proton transfer reactions between the acidic and basic oxygen sites mediated via a chain of the hydrogen bonded molecules in the first and second coordination shell of the reacting site.The results obtained in this study are general and applicable to the group of 2:1 phyllosilicates in a wide range of chemical and thermodynamic conditions.

New Insight Into Catalytic Mechanism of Glucose-6-Phosphate Dehydrogenase Enzyme: A DFT Study

The glucose-6-phosphate dehydrogenase (G6PD) enzyme plays a vital role in converting glucose-6-phosphate (G6P) to 6-phosphogluconolactone, as well as in reducing NADP([Formula: see text]) to NADPH. The Asp/His moiety of G6PD acts as a catalytic dyad in the active site of G6PD. This catalytic mechanism describes erythrocyte protection from oxidative stress and prevention of hemolysis; hence their exact understanding is important in the normal functioning of red blood cells. Herein, computational investigations were carried out to describe a plausible mechanism of the G6PD enzyme by using a series of DFT theoretical calculations using the M06-2X/6-31G ([Formula: see text], [Formula: see text]) basis set and performed in the following three discrete steps: (i) Proton transfer from His309 to Asp246, (ii) A subsequent proton transfer from G6P to His309, and (iii) A rate-limiting hydride transfer that reduces NADP([Formula: see text]) to NADPH. The final overall mechanism, therefore, results in the production of phosphogluconolactone and NADPH. The DFT calculations indicate that, in the absence of the His/Asp dyad, the chemical reaction changes from a low-energy sequential mechanism to the proposed concurrent mechanism with a very high energy barrier ([Formula: see text][Formula: see text]kcal[Formula: see text]mol[Formula: see text]). These results show that the Asp246 residue is responsible for transforming a high energy concurrent reaction into a low energy multistep sequential reaction in the G6PD enzyme for the production of NADPH. This work supports the study and design of the mechanism-based inhibitors and provides a detailed understanding of the catalytic mechanism of the enzyme thereby opening new possibilities towards an understanding of controlling detoxification processes due to premature breaking in red blood cells.

Isotope exchange between mercuric [Hg(II)] chloride and Hg(II) bound to minerals and thiolate ligands: Implications for enriched isotope tracer studies

Enriched mercury (Hg) stable isotopes have been widely used as tracers in field and laboratory investigations of Hg(II) biogeochemical transformations such as methylation and demethylation. Few studies, however, have considered concurrent isotope exchange reactions between newly spiked and pre-existing Hg(II) in environmental matrices, which may alter redistribution and thus transformation of the spiked and pre-existing Hg(II). Using enriched 198Hg [as mercuric Hg(II) or HgCln species], this study investigated isotope exchange between 198Hg and pre-existing Hg(II) bound to metacinnabar (β-HgS), sediments, low-molecular-weight (LMW) thiols, and dissolved organic matter (DOM). The impact of isotope exchange on methylmercury production in the presence of organic ligands was also evaluated with an iron-reducing bacterium Geobacter sulfurreducens PCA in a phosphate buffered solution (pH 7.4). We found that spiked 198Hg readily exchanged with mineral-bound ambient Hg(II) despite concurrent Hg(II) adsorption and immobilization on the solids. Rapid exchange (<3 min) was also observed between spiked 198Hg and 200Hg pre-equilibrated with LMW thiols and DOM in solution. While the exchange did not cause net changes in Hg(II) chemical speciation, it resulted in redistribution of Hg(II) isotopes bound to the ligands and thus an apparently similar methylation rate and magnitude of the spiked 198Hg and pre-existing 200Hg by PCA cells when 198Hg and 200Hg were added at 1:1 ratio. These observations underscore the importance of isotope exchange when an enriched Hg isotope is applied in environmental matrices, as the exchange could potentially lead to biased rate calculations of Hg(II) transformation and bioaccumulation and thus risk assessments of new Hg(II) input to the natural ecosystems.

A ZIF-triggered rapid polymerization of dopamine renders Co/N-codoped cage-in-cage porous carbon for highly efficient oxygen reduction and evolution

The ability to develop highly-efficient bifunctional electrocatalysts via facile and cost-effective routes is of practical interest for enabling concurrent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we report a simple yet robust strategy via zeolitic imidazolate framework (ZIF)-triggered rapid polymerization of dopamine for crafting cage-in-cage hollow porous carbon codoped with Co and N for highly-efficient ORR and OER electrocatalysts. First, dopamine (DA) is expeditiously polymerized on ZIF-67 within 10 min at room temperature, yielding yolk-shelled [email protected]x (denoted [email protected]x) particles with tunable PDA thickness. This contrast sharply to the copious past works where alkaline compounds are needed for the polymerization of DA. More importantly, the ZIF-67-triggered polymerization of DA is substantiated to undergo a coordination-dissociation-polymerization mechanism rendered by the synergistic effect of Co2+ and 2-methylamidazole. Subsequent one-step pyrolysis of [email protected] yields Co and N codoped cage-in-cage porous carbon (denoted Co/N CCPC-x). The resulting Co/N CCPC pyrolyzed at 600 °C manifests a superior ORR with the onset and half-wave potentials comparable to Pt/C and limiting current density larger than Pt/C, OER with low overpotential and potential difference, and Zn-air performance with high open-circuit voltage, specific capacity, power density and remarkable charge-discharge reversibility. Such impressive ORR and OER performances of Co/N CCPC are a direct consequence of simultaneous compositional (i.e., Co and N codoping) and structural (i.e., cage-in-cage architecture with hierarchical porosity) tailoring enabled by judicious PDA coating.

Optimisation of accelerated biodiesel production under near infrared radiation from de-oiled mustard and sunflower cakes

ABSTRACT An energy-efficient intensification protocol for biodiesel (fatty acid ethyl ester (FAEE)) production from the mustard de-oiled cake (MDC) and sunflower de-oiled cake (SDC) through concurrent esterification-transesterification reactions has been disclosed employing near-infrared radiation retrofitted batch reactor. The triglycerides and free fatty acids of the de-oiled cake were converted to FAEE through a one-pot synthesis in the presence of ethanol and one of the co-solvents viz. acetone, dimethyl sulfoxide (DMSO), and n-hexane. The optimal condition (75:1 (w/w) ethanol to de-oiled cake ratio, 70°C infrared radiation temperature, 2.5 wt. % H2SO4 catalyst concentration, and 1000 rpm stirrer speed) for maximum FAEE yield was evaluated deploying Taguchi L9 orthogonal method. Higher FAEE yield was achieved under infrared radiation for both MDC (82.4 ± 0.01%) and SDC (81.7 ± 0.02%), in comparison with the conventionally heated reactor (MDC: 56.1 ± 0.02%; SDC: 54 ± 0.02%) employing identical process condition. This enlightened the energy-efficacy of the infrared radiation in accelerating the FAEE yield within a much shorter reaction time. The FAEE composition was assessed by FTIR and GC-MS analyses. The fuel properties of the product biodiesel conformed to EN standards. Thus, a feasible and efficient protocol for the conversion of de-oiled cakes to biodiesel could be explored.

α‐Cationic Phospholes: Synthesis and Applications as Ancillary Ligands

A series of structurally differentiated α‐cationic phospholes containing cyclopropenium, imidazolium, and iminium substituents has been synthesized by reaction of chlorophosphole 1 with the corresponding stable carbenes. Evaluation of the donor properties of these compounds reveals that their strong π‐acceptor character is heavily influenced by the nature of the cationic group. The coordination chemistry of these newly prepared ligands towards AuI centers is also described and their unique electronic properties exploited in catalysis. Interestingly, α‐cationic phosphole containing catalysts were not only able to accelerate model cycloisomerization reactions, but also to efficiently discriminate between concurrent reaction pathways, avoiding the formation of undesired product mixtures.