Kinds Of Reactions Research Articles

Spontaneous synthesis of a homogeneous thermoresponsive polymer network composed of polymers with a narrow molecular weight distribution

We have developed a method to obtain a polymer gel consisting of a relatively homogeneous network structure composed of polymers with a narrow molecular weight simply by mixing the necessary compounds. In this method, a radical chain polymerization reaction with a fast reaction rate is combined with a radical addition cross-linking reaction that has a sufficiently slow reaction rate compared with the polymerization reaction. For the polymerization reaction, a multifunctional initiator with a strictly controlled number of polymerization initiation sites was used to prepare a star polymer with a chain number and length determined by living radical polymerization. In the cross-linking reaction, a multifunctional terminating agent was used to prepare a star polymer from a polymer with a narrow molecular weight via living radical polymerization followed by coupling with multiple polymer chains using a termination reaction. As a result, two kinds of reactions with greatly different kinetics occurred sequentially only when all of the compounds were mixed and allowed to stand at a constant temperature, and a relatively homogeneous network structure comprising cross-linked polymers with a low molecular weight distribution was inherently constructed.

Alkyl Radical Generation by an Intramolecular Homolytic Substitution Reaction between Iron(II) and Trialkylsulfonium Groups.

Intramolecular, homolytic substitution reactions between iron(II) species and various trialkylsulfonium groups were directly observed in the gas phase upon collision-induced dissociation. In spite of the notoriously low reduction potential of trialkylsulfonium species and the mismatched oxidation potential of iron(II), the reactions proceed at moderate collision energies, forming an alkyl radical as well as a thioether coordinated to the iron. In contrast to classical homolytic substitutions, the attacking radical is a "metalloradical", namely iron(II) that is oxidized to iron(III) during the reaction. With this process we demonstrate that the conceptually analogous, putative radical generation step in radical S-adenosyl methionine (SAM) enzymes is possible and plausible. Further, we show that this kind of reaction only occurs in constrained systems with a defined geometry. Combining experimental measurements with DFT studies and NBO analyses allowed us to gain insights into the reactivity and transition states of these systems. Based on our findings, we challenge the notion of a collinear transition state in the radical generation step of radical SAM enzymes and propose it to be bent instead.

Enzymatic Study of Linoleic and Alpha-Linolenic Acids Biohydrogenation by Chloramphenicol-Treated Mixed Rumen Bacterial Species.

In the rumen, dietary polyunsaturated fatty acids (PUFA) are reduced by a multistage reaction called biohydrogenation (BH). BH leads to a high proportion of saturated fat in ruminant products, but also products some potential bioactive intermediates like conjugated linoleic and linolenic acids. BH is composed of two kinds of reactions: first an isomerization of PUFA followed by reductions (two for linoleic acid, C18:2n-6; three for α-linolenic acid, C18:3n-3). There is little knowledge about BH enzymes as BH bacterial species are the subject of a lot of studies. Nevertheless, both aspects must be explored to control BH and enhance the fatty acids profile of ruminant products. In the present study, an alternative approach was developed to study the enzymes produced in vivo by mixed ruminal bacteria, using inactivation of bacteria by chloramphenicol, an inhibitor of protein synthesis in prokaryotes, before in vitro incubation. To study C18:2n-6 and C18:3n-3 BH several experiments were used: (1) with different incubation durations (0 to 3) to estimate average rates and efficiencies of all BH reactions, and intermediates production; and (2) with different initial quantities of PUFA (0.25 to 2 mg) to estimate Michaelis–Menten enzymatic parameters, Km and Vmax. A last experiment explored the effect of pH buffer and donor cow diet on C18:2n-6 isomerization pathways. Concerning C18:2n-6 BH, this study confirmed the high saturability of its isomerization, the inhibition of both trans11 and trans10 pathways by a low pH, and the last reduction to stearic acid as the limiting-step. Concerning C18:3n-3, its BH was faster than C18:2n-6, in particular its isomerization (Vmax = 3.4 vs. 0.6 mM/h, respectively), and the limiting-step was the second reduction to t11-C18:1. Besides, our mixed isomerases had a higher affinity for C18:2n-6 than for C18:3n-3 (Km = 2.0 × 10-3 vs. 4.3 × 10-3 M, respectively), but due to their high saturability by C18:2n-6, they had a lower efficiency to isomerize C18:2n-6 than C18:3n-3. Chloramphenicol-treated ruminal fluid would be a meaningful method to study the BH enzymes activities.

Effect of CeO2 morphologies on toluene catalytic combustion

Catalytic combustion is an efficient and economic technology to eliminate toluene, and CeO2 shows very good performance in this kind of reactions. In this work, three kinds of CeO2 catalysts with different morphologies (rod, hollow sphere and cube) have been prepared, and there performances for toluene catalytic combustion were compared. It is found that CeO2-HS shows the best catalytic activities for toluene degradation. Toluene conversion could get 90% at 207 °C. That’s because CeO2-HS catalyst have largest surface area and most oxygen vacancies, which are vital for toluene catalytic oxidation. CeO2-HS also shows very good catalyst stability, reusability and excellent tolerance to water.

N-doped graphene combined with alloys (NiCo, CoFe) and their oxides as multifunctional electrocatalysts for oxygen and hydrogen electrode reactions

Highly efficient and low-cost nanomaterials with multifunctions for oxygen evolution reaction (OER), hydrogen evolution reaction (OER) and oxygen reduction reaction (ORR) have been attracted tremendous attentions that play significant roles in energy storage and conversion. Herein, a facile strategy is developed to synthesize metal alloys (NiCo, CoFe) with their oxides supported on nitrogen-doped graphene (N-rGO/NiCo-NiO-CoO, N-rGO/CoFe-Co2FeO4). The obtained nanomaterials exhibit outstanding tri-functional performances for the above mentioned three kinds of reactions. Furthermore, the prepared composites, assembled in air cathodes, present excellent performance that are similar with Pt/C or Pt/C + IrO2 in primary and rechargeable zinc-air batteries. The prepared N-rGO/NiCo-NiO-CoO and N-rGO/CoFe-Co2FeO4 exhibit the specific capacities of 734 and 711 mA h gZn−1 at the current density of 20 mA cm−2, respectively. The rechargeable zinc-air batteries maintain excellent durability after cycling 33 h.

Catalytic activities of heterogeneous catalysts obtained by copolymerization of metal-containing 2-(acetoacetoxy)ethyl methacrylate

Abstract Among the synthetic strategies commonly used for supporting a metal complex onto an organic polymer in order to obtain an heterogenous catalyst, a valid choice is to synthesize a metal containing monomer (MCM), which can subsequently be subjected to polymerization with suitable comonomers and crosslinkers, achieving a supported transition metal catalyst as a metal-containing polymer (MCP). In this context, during the last two decades, we explored the use of 2-(acetoacetoxy)ethyl methacrylate (HAAEMA) as a ligand to prepare several MCMs for the relevant MCPs. In this review we summarize and discuss our developments in the studies of the catalytic activity of these “hybrid” catalysts. These catalysts have demonstrated high efficiency and/or excellent selectivity in several kinds of chemical reactions and very often they could be recovered and reused in multiple cycles maintaining their activity and selectivity without suffering from appreciable metal leaching.

Fe-ZSM-5 supported palladium nanoparticles as an efficient catalyst for toluene abatement

Catalytic combustion is considered as an efficient and economic technology to remove VOCs, and Al-ZSM-5 zeolite supported palladium catalysts (Pd/Al-ZSM-5) with good performances in this kind of reactions have been reported. In this work, it is found that Fe-ZSM-5 supported palladium catalyst (Pd/Fe-ZSM-5) exhibit higher catalytic activity in toluene combustion than the Pd/Al-ZSM-5, which is strongly related to more Pd0 active species and higher concentration of absorbed oxygen species of Pd/Fe-ZSM-5 than those of Pd/Al-ZSM-5. More importantly, Pd/Fe-ZSM-5 has a good catalyst life and water-resistant ability, which should be potentially significant for practical applications in environment protection.

Hymenoptera sting reactions in southern Italy forestry workers: our experience compared to reported data

BackgroundHymenoptera sting reactions are among life-threatening causes of allergy. Several epidemiology studies have assessed the risk of these kind of reactions, among the general population, around 3% of adults. This incidence increases among highly at risk populations such as outdoor workers. Hymenoptera stings among forestry workers (FW) are occupational triggers but it has not yet been well defined which is the real incidence of anaphylaxis in these workers, not even in Italy. Two Italian studies reported on the risk of hymenoptera stings (HS) in northern Italy (NI) and central Italy (CI) FW while no data is available on the prevalence in southern Italy (SI) ones.MethodsA population of 341 SI FW (301 males and 40 females, mean age 51 years, range 43–63 years), who worked in Sicily, was investigated submitting a standardized questionnaire dealing with reactions to Hymenoptera stings, such as large local reactions (LLR) and systemic reactions (SR).ResultsHS occurred in 203 FW (59%) and caused reactions in 77 (22%); LLR occurred in 46 (13%) and SR in 31 (9%); SR were life threatening in 9/341 (3%) FW and were treated with epinephrine at the emergency unit as workers did not carry an epinephrine auto-injector. A SR at a subsequent HS followed a LLR in 21/46 FW (46%).ConclusionsFW in SI have a generic risk of HS anaphylaxis as in the general population but a higher risk of SR and LLR respect to forestry populations from different Italian geographical areas.SR among SI FW occurred in 9% of them, while published data report the incidence of SR around 2 and 4%, respectively, in the Centre and North Italy FW. The incidence of LLR in SI FW was also higher (13%) than in CI (2%) and NI (10%) ones. Previous LLR in our SI population represented a high risk factor for developing a SR and therefore a red flag for future anaphylaxis and prescription of an epinephrine auto-injector.

Revised Mechanism for a Ruthenium-Catalyzed Coupling of Aldehyde and Terminal Alkyne.

Ruthenium catalysts have been found to be of great use for many kinds of reactions. Understanding the details of the catalytic cycle allows to not only rationalize experimental results but also to improve upon reactions. Herein, we present a detailed computational study of a ruthenium-catalyzed coupling between a terminal alkyne and an aldehyde. The reaction under examination facilitates novel access to olefins with the concurrent loss of a single carbon as carbon monoxide. The reaction was first developed in 2009, but the tentative mechanism initially proposed was proven to be contradictory to some experimental data obtained since then. Using a combination of computational investigations and isotope-labeling experiments, several potential mechanisms have been studied. In contrast to the [2+2] cycloaddition mechanism suggested for similar catalysts, we propose a new consensus pathway that proceeds through the formation of a ruthenium–vinylidene complex that undergoes an aldol-type reaction with the aldehyde to yield the product olefins. Computational insights into the influence of different reagents used to optimize reaction conditions and the intricacies of decarbonylation of a Ru–CO complex affecting catalyst turnover are highlighted.

OXIDATION OF FERRIC XYLENOL ORANGE CHELATES BY HYDROGEN PEROXIDE IN AQUEOUS SOLUTION: CONCEPTION OF OXYGEN SINGLET ATOMS GENERATION FROM HYDROGEN PEROXIDE

We observed for the first time the reaction of oxidation of ferric xylenol orange chelates by hydrogen peroxide in aqueous solution. The reaction is accompanied with decoloration of the violet aqueous solution. Based on generally accepted conception, there is a process of free radical chain oxidation of indicator molecule in the solution. However, after investigating the final colorless solution by 1H NMR-spectroscopy we found the modified but not broken structure in which the initial hydrocarbon core remained mainly unchanged. We concluded that kind of reaction was an oxyfunctionalization by hydrogen peroxide versus free radical chain destruction. We argued steps of the reaction such as N-oxidation, Cope’s elimination, and certain rearrangements with possible products oligomerization. There was a need to explain the mechanism of interaction between the ferric iron ion and the hydrogen peroxide molecule and to argue the nature of intermediate reactive oxygen species. There is similarity between the ferric-catalyzed hydroperoxide xylenol orange oxidation and the peroxygenase-catalyzed biochemical oxyfunctionalization reactions. However, based on literature data and molecular orbital modeling, we proposed another mechanism of interaction between the ferric iron ion and the hydrogen peroxide molecule instead the tetravalent iron generation. Concretely, we proposed the hydrogen peroxide zwitter-ionization (isomerization to oxywater molecule) and subsequent intramolecular disproportionation with generation of a water molecule and a singlet oxygen atom as a reactive oxygen species. In this view, the iron ion oxidation state is unchanged during the reaction and remains ferric. An oxyfunctionalization of any organic substrate by hydrogen peroxide in the presence of ferric iron ions is promising approach in organic synthesis. However, the usage of organic ligands for ferric iron ions as components of catalysts is limited and requires only non-oxidizable compounds. On the other hand, one can choose an oxidation substrate as a ligand for ferric iron ions that is the formation of chelate complex of ferric catalyst with an organic substrate.Forcitation:Chumakov A.A., Kotelnikov O.A., Slizhov Yu.G. Oxidation of ferric xylenol orange chelates by hydrogen peroxide in aqueous solution: conception of oxygen singlet atoms generation from hydrogen peroxide. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 15-22

Covalent Bonding of Chlorogenic Acid Induces Structural Modifications on Sunflower Proteins.

Proteins and phenols coexist in the confined space of plant cells leading to reactions between them, which result in new covalently bonded complex molecules. This kind of reactions has been widely observed during storage and processing of plant materials. However, the nature of the new complex molecules and their physicochemical properties are largely unknown. Therefore, we investigated the structural characteristics of covalently bonded complexes between sunflower protein isolate (SFPI, protein content 85 wt %) and the dominant phenol in the confined space of a sunflower seed cell (chlorogenic acid, CGA). It was shown that the efficiency of bond formation goes through a maximum as a function of the SFPI:CGA ratio. Moreover, the bonding of CGA with proteins resulted in changes in the secondary and tertiary structure of the protein. It was also shown that the phenol bound strongly to the protein, which resulted in new crosslinks between the polypeptide chains. As a result, secondary structures like α-helices and β-sheets diminished, which in turn resulted in more disordered domains and a subsequent modification of the tertiary structure of the proteins. These findings are relevant for establishing future protocols for extraction of high-quality proteins and phenols when utilizing plant material and offer insight into the impact of processing that these ingredients endure.

Effect of Ceria on redox-catalytic property in mild condition: A solvent-free route for imine synthesis at low temperature

Five different nanocerias were prepared and used to catalyze the direct coupling of alcohol and amine to the corresponding imines under air atmosphere at low temperature. The catalytic efficiencies have great differences, CeO2 prepared by coprecipitation at room temperature (called CeO2-5) has the best catalytic activity, whose yield reaches 99% at 303 K for 36 h, 100 times higher than the nano-octahedras ceria (called CeO2-4) and also higher than the catalytic performance of most reported catalysts. Such phenomena are ascribed to the higher acidic sites, specific surface area, and proportions of surface oxygen. The results of DRIFTS demonstrated that the alcohol oxidized to benzaldehyde was the rate determining step in this reaction. Furthermore, CeO2-5 still shows excellent catalytic performance on 10-fold magnification experiments without any addition of solvent. Besides, it has the advantages of simple process, low energy consumption and practical scaling-up as well as good universality towards this kind of reaction, showing every prospect in industrial application.

Kontribusi Pemikiran Egbert Schuurman mengenai Permasalahan dan Solusi Teknologi Modern

ABSTRACT:In the modern technological world, human is constantly relating with technology, be it as a user or as a part of technological production mechanism. But what is technology, what kind of value that technology brings, and how should one response to technology? Does technology brings good, bad or neutral? These are the questions that we need to answer as we live in a technological world. In the philosophy of technology, there is one thinker, who represents the school of Reformational Philosophy, named Egbert Schuurman. In the midst of two kinds of reaction towards technology (optimistic and pessimistic) Schuurman proposes a Liberating Perspective as the third option. This perspective is aware of the deep influence of human sinfulness in technological development. However, it also considers the beauty of creational design and Christ’s redeeming power for technological development. In this article, the writer would like to observe Schuurman’s thoughts regarding this Liberating Perspective as a considerable solution to the problems of modern technological life. KEY WORDS: technology, modern, society, reformational philosophy, liberating perspectives, responsible ethics

Development of Cultural Construction and Constitutional Revolution in Iran

The subject of this article is the development of the cultural construction and the emergence of the Constitutional Revolution in Iran. This study, by examining the cultural structure of the Qajar era of the Naser-al-Din Shah period wants to investigate the cause of the Constitutional Revolution.The findings of this research, which have been collected by historical-analytical method, indicate that the pattern of development in the Qajar era is consistent with the pattern of unbalanced development. In this sense, by starting educational, political and military reforms in the Qajar era specially Nasser-al-Din Shah, gradually the cultural structure apart from the traditional political structure. This development provided the basis for the emergence of new intellectuals and elites with new political ideas in the field of governance methods. However, the attenuation of political structure and the backwardness of political development from cultural development faced with some obstacles. Political system instead of creating a development along with gradual cultural development and consolidating its position through the persuasion of the community, in fact to maintain integrity in the social system was resorted to force and preferred force and compulsion to persuasion. The kind of reaction and opposition of the political power structure against the modern intellectual movement, which contained new political demands in the area of governance and freedom, led to the weakness and, finally, the collapse of the Qajar political system and the constitutional revolution.

Quando a cor é um problema: reação ao pigmento vermelho de tatuagem. Um relato de caso

The body art, including the tattoo, is a rising popular practice in the contemporary world. Though the growing interest in this practice, one should be aware of this technique’s risks. This article reports a case of a 35 year old man, with no relevant prior diseases, who schedules an appointment with an exuberant pruritic inflammatory reaction in the anterior forearm of the left upper limb, 48h after tattooing the same area. At physical examination, there was a wide exudative erythematous surface restricted to the red pigment area of the tattoo and skin integrity on other colors areas. A scheme of antibiotic therapy and wound care was instituted, with infection resolution but with lichenified texture restricted to the red pigment color area. An oral and topical corticosteroid regimen was performed with improvement of the condition. Comment: there are various complications described in response to tattoos. The pigment reaction is one of the many. The evolution of the skin’s reaction to the tattoo’s ink can be variable and it can manifest in days, weeks or years. The red paint compounds are the most implicated in these kind of reactions. This case emphasizes the importance of general population/health professionals knowledge of the potential complications of this practice as well as the kind and origin of the ink pigments used to make it.

Synthesis and characterization of polyvinylmethylsiloxanes by cationic polymerization using a solid green catalyst

AbstractThe present work is devoted to the synthesis and characterization of vinylsiloxane polymers produced by the use of an activated natural catalyst known as Maghnite-H+. The cationic ring opening polymerization of pentavinylpentamethylcyclopentasiloxane (V5D5) made it possible to obtain the desired polymeric materials. Through this study, we have adapted a new strategy of synthesis of a siloxane polymer with relatively high molecular mass, using a solid initiator activated by sulfuric acid, which has enabled us to combine the ecological aspect of synthesis and the effectiveness of the catalyst in this kind of reaction. Structural [infrared (IR), proton and carbon nuclear magnetic resonance (1H NMR and13C NMR)], thermal differential scanning (DSC) and chromatographic (GPC) characterization methods have allowed the products obtained to be identified and their various properties to be focused on. The kinetic study was made to determine the order of the reaction. The proposed reaction mechanism shows the advantages of Maghnite-H+.

Rechterlijke discretie voor de privaatrechtelijke reactie op ongewenst gedrag

On the basis of a philosophical distinction between 'bad' and 'evil' behaviour the author distinguishes several kinds of reactions towards undesirable behaviour, which would explain various contradictory tendencies in case law.

A DFT Study on Mechanisms and Origin of Selectivity of Phosphine-Catalyzed Vicinal Acylcyanation of Alkynoates

The mechanisms of phosphine-catalyzed vicinal acylcyanation of alkynoates have been firstly investigated by density functional theory. Both PPhMe2- and PBu3-catalyzed reactions were enumerated and studied in detail. For each reaction, three possible pathways, including the direct pathway that leads to syn-selective product and two phosphine-catalyzed reaction pathways that lead to anti- and syn-selective products respectively, were considered in this work. The calculated results indicate that the most energetically favorable pathway contains five reaction steps: the nucleophilic attack on alkynoate by phosphine, the acylation by acylcyanide, the dissociation of CN group from acylcyanide, the addition of CN group to olefin carbon of alkynoate part, and the dissociation of phosphine and product. The last two steps are the key for the anti/syn-selectivity of reactions, and our computational results can reasonably explain the experimental observations. In addition, non-covalent interaction analysis was performed for exploring the origin of the anti/syn-selectivity. Moreover, the natural bond orbital (NBO) population and global reactivity index (GRI) analyses were also carried out to disclose the role of the phosphine catalyst in this kind of reaction. This work should be helpful for chemists to understand the detailed mechanisms and predict anti/syn-selectivity of this kind of vicinal acylcyanation.

A theoretical study on synthesis mechanisms of α,β-unsaturated carbon γ-amino ester catalyzed by PPh3

In this paper, generation mechanism of α,β-unsaturated carbon γ-amino esters catalyzed by triphenylphosphine (PPh3) have been investigated using density functional theory (DFT). Two possible mechanisms (Mechanism A and Mechanism B) are proposed, in which there are three possible reaction pathways (Path A1/A2/A3 in Mechanism A and Path B1/B2/B3 in Mechanism B) except for the generation of the intermediate M1. The calculated results demonstrate that the energy favorable pathways (Path A2 and Path B2) include three process: the first step is an intermolecular proton transfer accompanied by a nucleophilic attack, the second step is an intramolecular proton transfer process, and the last step is the dissociation of PPh3 and the product generation. Furthermore, the reaction pathway associated with the E-isomer is the most favorable pathway and leads to the main product (E-P), which is in good agreement with the experimental results. This work might be helpful for understanding the significant roles of catalyst PPh3 and thus provide valuable insights on the rational design of potential catalysts for this kind of reactions.

Direct coupling of electromembrane extraction to mass spectrometry - Advancing the probe functionality toward measurements of zwitterionic drug metabolites

A triple-flow electromembrane extraction (EME) probe was developed and coupled directly to electrospray-ionization mass spectrometry (ESI-MS). Metabolic reaction mixtures (pH 7.4) containing drug substances and related metabolites were continuously drawn (20 μL/min) into the EME probe in one flow channel, and mixed inside the probe with 7.5 μL min−1 of 1 M formic acid as make-up flow from a second flow channel. Following this acidification, the drug substances and their related metabolites were continuously extracted by EME at 400 V, across a supported liquid membrane (SLM) comprising 2-nitrophenyl octyl ether (and for some experiments containing 30% triphenyl phosphate (TPP)), and into 20 μL min−1 of formic acid as acceptor phase, which was introduced through a third flow channel. The acceptor phase was pumped directly to the MS system, and the ion intensity of extracted analytes was followed continuously as function of time. The triple-flow EME probe was used for co-extraction of positively charged parent drugs and their zwitterionic drug metabolites (hydroxyzine and its carboxylic acid metabolite cetirizine; and vortioxetine and its carboxylic acid metabolite Lu AA34443). While the zwitterionic metabolites could not be extracted at pH 7.4, it was shown that by acidifying the sample solution the zwitterionic metabolites could be extracted effectively. Various extraction parameters like make-up flow, extraction voltage and SLM composition were optimized for simultaneous extraction of parent drugs and metabolites. It was found that TPP added to the SLM improved extraction efficiencies of certain drug metabolites. Finally the optimized and characterized triple-flow EME probe was used for online studying the in-vitro metabolism of hydroxyzine and vortioxetine by rat liver microsomes. Due to the automated pre-extraction acidification of the rat liver microsomal solutions, it was possible to continuously monitor formation of the zwitterionic drug metabolites. As the triple-flow EME probe allowed modification of the pH of the sample without changing the pH in the bulk sample, the system can potentially be used for direct analysis of various kinds of chemical reactions that have to be run at pH conditions unfavorable for direct analyte extractions.