Main Reaction Products Research Articles

Biochemical diagnosis of aromatic-L-amino acid decarboxylase deficiency (AADCD) by assay of AADC activity in plasma using liquid chromatography/tandem mass spectrometry

Aromatic l-amino acid decarboxylase (AADC, EC 4.1.1.28) deficiency is a rare genetic disorder characterized by developmental delay, oculogyric crises, autonomic dysfunction and other problems, caused by biallelic mutations in the DDC gene leading to deficient activity of aromatic l-amino acid decarboxylase, an enzyme involved in the formation of important neurotransmitters, such as dopamine and serotonin. A clinical development program of gene therapy for AADC deficiency is ongoing. An important step for the success of this therapy is the early and precise identification of the affected individuals, but it has been estimated that around 90% of the cases remain undiagnosed. The availability measurement of the AADC activity is mandatory for an accurate biochemical diagnosis. Based on these statements, our objectives were to develop a liquid chromatography tandem mass spectrometry (LC-MS/MS) method suitable for the determination of the AADC activity, and to evaluate its capacity to confirm the deficiency of AADC in potential patients in Brazil. The AADC activities were measured in plasma samples of seven AADC deficient patients and 35 healthy controls, after enzymatic reaction and LC-MS/MS analysis of dopamine, the main reaction product. The results obtained showed clear discrimination between confirmed AADC deficient patients and healthy controls. The method presented here could be incorporated in the IEM laboratories for confirmation of the diagnosis of when a suspicion of AADC deficiency is present due to clinical signs and/or abnormal biomarkers, including when an increased level of 3-O-methyldopa (3-OMD) is found in dried blood spots (DBS) samples from high-risk patients or from newborn screening programs.

Fusion of phosphate by-products and glass waste for preparation of alkali-activated binders

Landfilling of mine and industrial waste streams leads to environmental and economic issues. Sustainable management methods through valorization in manufacturing green construction materials are a current research interest. Here, a promising process for recycling mine tailings, such as phosphate sludge, is proposed. A mixture of phosphate sludge, kaolin clay (Al source), and glass waste (Si source) was prepared. Three fluxing agents were tested at 1000 °C (NaOH, Na2CO3, Na2SO4). Na2CO3 was selected as the most cost-effective. The precursors were alkaline activated with NaOH solution (2, 6, and 8 M). At 28 days of curing (20 h room temperature + 6 h 85 °C + room temperature), the best compressive strength (of more than 45 MPa) was obtained with 8 M NaOH. The reaction products, characterized by XRD, FTIR, SEM, and MAS NMR, show that the main reaction products is a gel N–A–S–H/(N,C)–A–S–H together with some unreacted crystalline phases formed during the fusion.

Influence of the type and concentration of the activator on the microstructure of alkali activated SiMn slag pastes

The influence of the type and concentration of the activator on the composition of the products formed and the microstructural development of alkali activated SiMn slag pastes and their evolution with curing time are studied. About 15–17 million tons of SiMn slag is produced per year, so valorising this residue is interesting for the economic and environmental scope. For this purpose, NaOH and WG with different concentrations of Na2O have been used as activators. The hydration products have been studied by X-ray diffraction analysis (XRD) and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDX) has been used to study the microstructure and elemental composition of hydrated phases. The advance of the degree of hydration with time and with the activator concentration is consistent with the mechanical behaviour of these pastes observed in previous studies. All the pastes show high microcracking due to the stresses caused by the shrinkage, as it has been observed in previous studies. Elemental composition data do not show significant differences regarding the type of activator with respect to the main elements and their relationship in the reaction products except for Mn. The main reaction product formed in the alkaline activation of SiMn slag is C-S-H with a low Ca/Si ratio, this being higher for pastes activated with NaOH compared to those with WG. In addition, the modification of the C-S-H structure is demonstrated by the presence of small amounts of Al and Mn and that Mg is not incorporated into it. The presence of hydrotalcite is not detected by XRD, but small amounts have been confirmed by TGA/DTG and SEM/EDX.

Hydration kinetics and performance of sodium carbonate-activated slag-based systems containing reactive MgO and metakaolin under carbonation

The hydration mechanism and strength development of sodium carbonate-activated slag-based systems mainly depend on the additives used. Although the effects of mineral additives in such systems have been extensively investigated, the effects of Mg2+, Al3+, and Si4+ ions increasing with the addition of reactive MgO (Mg) and metakaolin (Mk) on the hydration mechanism of such systems have not been established yet. This study investigated the hydration kinetics and performance of sodium carbonate-activated ternary blended slag-based binder systems. The hydration mechanism was revealed by isothermal calorimetry and mechanical performance was evaluated with the measurement of compressive strength at different ages up to 56 days. The reaction mechanisms were investigated through X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and 29Si and 27Al solid-state nuclear magnetic resonance (NMR). C-(A)-S-H, Na and Al-enriched C-(N,A)-S-H and hydrotalcite were the main reaction products responsible for the strength development of the samples, accompanied by the minor contribution of other carbonate-containing phases. Partial replacement of slag with Mg and Mk led to high early-age strengths compared to plain samples when Mk was used at 5%. Samples incorporating Mg and Mk achieved similar or higher strengths than ordinary Portland cement-based samples. However, an increase in replacement ratio of Mk beyond 5% led to a significant decrease in compressive strength. Furthermore, the performance of samples under accelerated carbonation was studied. The use of Mg and Mk enhanced carbonation resistance due to enhanced hydrotalcite and C-(N,A)-S-H gel formation, highlighting the potential of using slag-Mg-Mk blends as an alternative binder system.

Study on the mechanism of hydrodesulfurization of tetrahydrothiophene catalyzed by nickel phosphide

Hydrodesulfurization (HDS) reaction can significantly reduce the viscosity and sulfur content of heavy oil, while the HDS reaction mechanism of tetrahydrothiophene as the main sulfide in heavy oil is still unclear. The HDS experiment of tetrahydrothiophene catalyzed by nickel phosphide (Ni2P) is carried out at 200–300 °C. The results indicate that the H2S production under the catalysis of Ni2P increases obviously within 200–250 °C. The main gas products of HDS reaction are butane, butene and H2S. Meanwhile, the mechanism of tetrahydrothiophene catalyzed by Ni2P is analyzed based on Density Functional Theory (DFT). It is revealed that the adsorption model is most stable when tetrahydrothiophene is vertically adsorbed on the V–Ni-Hcp1 site of Ni2P (001). The C–S bond is elongated and the C–C bond is shortened after adsorption. Hydrogenation (HYD) is the most possible reaction route of tetrahydrothiophene on Ni2P (001) surface. There are two routes with the lowest activation energy, which are C4H8S→C4H8SH∗→C4H9SH∗→C4H10+H2S and C4H8S→C4H9S∗→C4H9∗+SH∗→C4H10+H2S. Butane and H2S are produced in the reaction, corresponding to the experimental results. This study provides a basis for understanding of the HDS mechanism of tetrahydrothiophene catalyzed by Ni2P.

Effect of polymer latex on the efflorescence, drying shrinkage and microstructure of alkali-activated slag paste

This study investigated the performance of alkali-activated slag (AAS) paste modified with different levels of styrene-acrylic resin (SAR) polymer latex. The AAS paste samples were prepared using GGBFS of two different fineness levels and NaOH solutions with respective molarities of 10 M, 12 M, and 14 M. Polymer latex was added at levels of 2.5%, 5%, and 7.5% of GGBFS weight. The AAS paste with fine GGBFS and NaOH 12 M performed the better strength than that with coarse GGBFS. The AAS paste samples modified with SAR polymer latex up to 5% exhibited slightly increased compressive strength results but reduced the ultrasonic pulse velocity (UPV) values. Furthermore, the addition of polymer latex enhanced the microstructure and significantly reduced efflorescence and drying shrinkage results. C-(A)-S-H gel and hydrotalcite phase were the main reaction products of both the latex-free and latex-modified AAS paste samples, with no new reaction products generated by the addition of polymer latex.

An experimental study of the reactivity of terpinolene and <i>β</i>-caryophyllene with the nitrate radical

Abstract. Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. They can rapidly react with the nitrate radical (NO3) during the nighttime to form a number of functionalized products. Among them, organic nitrates (ONs) have been shown to behave as reservoirs of reactive nitrogen and consequently influence the ozone budget and secondary organic aerosols (SOAs), which are known to have a direct and indirect effect on the radiative balance and thus on climate. Nevertheless, BVOC + NO3 reactions remain poorly understood. Thus, the primary purpose of this study is to furnish new kinetic and mechanistic data for one monoterpene (C10H16), terpinolene, and one sesquiterpene (C15H24), β-caryophyllene, using simulation chamber experiments. These two compounds have been chosen in order to complete the few experimental data existing in the literature. Rate constants have been measured using both relative and absolute methods. They have been measured to be (6.0 ± 3.8) ×10-11 and (1.8 ± 1.4) ×10-11 cm3 molec.−1 s−1 for terpinolene and β-caryophyllene respectively. Mechanistic studies have also been conducted in order to identify and quantify the main reaction products. Total organic nitrates and SOA yields have been determined. Both terpenes appear to be major ON precursors in both gas and particle phases with formation yields of 69 % for terpinolene and 79 % for β-caryophyllene respectively. They are also major SOA precursors, with maximum SOA yields of around 60 % for terpinolene and 90 % for β-caryophyllene. In order to support these observations, chemical analyses of the gas-phase products were performed at the molecular scale using a proton transfer reaction–time-of-flight–mass spectrometer (PTR-ToF-MS) and FTIR. Detected products allowed proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.

Brazing of TiAl and Ti2AlNb alloys using high-entropy braze fillers

To address the excessive formation of brittle compounds when brazing TiAl alloys, a TiZrHfCoNiCu high-entropy brazed filler was developed to realize the brazing of TiAl/Ti 2 AlNb couples. The TiAl/Ti 2 AlNb brazed joints can be divided into 4 zones, i.e., 2 diffusion zones at the TiAl/braze filler, Ti 2 AlNb/braze filler interfaces and 2 zones divided inside the brazed seam. α 2 + γ-TiAl were the main reaction products formed at the TiAl/braze filler interface and α 2 + Ti 0.5 Al 0.12 Nb 0.38 were the main reaction products at the Ti 2 AlNb/braze filler interface. Effects of brazing temperatures on the interfacial microstructure and mechanical properties of the TiAl/Ti 2 AlNb brazed joints were investigated. When brazing at 1100°C/15 min, the highest shear strength can reach 157 MPa (room temperature), and 123 MPa (650°C) respectively. The relationship between the microstructure and the corresponding mechanical response were discussed in detail. This research can offer new insights on developing desirable brazing filler when joining TiAl and TiAl based alloys. • A TiZrHfCoNiCu high-entropy alloy braze filler was developed to realize the brazing of TiAl/Ti2AlNb couples. • Ti 0.5 Al 0.12 Nb 0.38 and α 2 + γ-TiAl formed at the braze filler/base metal interfaces were the key to realize the joining. • The α 2 + γ-TiAl at the TiAl/braze filler interface was preferential to crack for the strongest brazed joints. • Highest shear strength of 157 MPa (room temperature) and 123 MPa (650°C) were achieved at 1100°C/15 min.

Ozonation of 4-aminotoluene as a new method of synthesis of 4-aminobenzaldehyde – an intermediate for the production of anti-tuberculosis drugs

Solutizon is an original anti-TB drug that is effective in resisting mycobacteria to other anti-TB drugs, which is obtained by the interaction of thiosemicarbazone 4-aminobenzaldehyde and sodium oxymethylene sulfonate. 4-Aminobenzaldehyde is synthesized by redox conversion of 4-nitrotoluene in the presence of sodium polysulfide. The reaction is carried out in boiling alcohol, and 4-aminobenzaldehyde is separated after steam distillation with a yield of 40–50 %. However, today this method loses its practical, environmental and economic attractiveness, as it has significant disadvantages – low product yield, high reaction temperature (80–120 °C), the formation of sulfur-containing wastewater. Therefore, the development of low-temperature, environmentally friendly methods for obtaining 4-aminobenzaldehyde is an urgent task. The aim of the work is to study the kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene to create a new low-temperature, environmentally friendly method for the synthesis of 4-aminobenzaldehyde. Materials and methods. Sigma acetic anhydride of сh.р. qualification was used for the experiments. 4-Aminotoluene company “Sinbias” qualification “сh.р.”; 4-Acetamidotoluene and its derivatives were used chromatographically pure. Acetates of metals of qualification “сh.р.”, potassium bromide of qualification “pharmacopoeial” were used without additional purification. Continuous control of the current ozone concentration and recording the results in the form of a kinetic curve was carried out when passing ozone-containing gas through the container of the spectrophotometer “SF-46 LOMO” at a certain wavelength of a monochromatic light source. The results of the analysis were recorded using the KSP-4 potentiometer included in the spectrophotometer optical density reference circuit. This device automatically compensated the photocurrent by recording its value. The scale KSP-4 was calibrated in units of optical density, and the conversion into absolute ozone concentration was carried out according to the Lambert-Ber equation using molar extinction coefficients. Relative analysis error ≤5 %. At the optical stroke length of the container 10 ÷ 100 mm, the sensitivity of the device was ~10-7mol·l-1 ozone. Results. The kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene have been studied. It is shown that the developed catalytic system Mn(II)-KBr-H2SO4-Ac2O significantly increases the depth, rate, and selectivity of oxidation of 4-aminotoluene and the main reaction product is 4-aminobenzaldehyde in the form of the corresponding benzylidenediacetate with a yield of 69.5 %. The active particle responsible for the inclusion of the substrate in the oxidation of the methyl group in the presence of manganese (II) acetate and potassium bromide is manganese bromide ion radical (Mn(II)Br•), which is more active than Mn (III) and therefore more high-speed initiates oxidation by the methyl group. Conclusions. Catalytic systems have been developed that allow the oxidation of ozone to be directed mainly to the methyl group of 4-aminotoluene and to stop the reaction at different oxidation depths. It was found that manganese (II) acetate, which has a relatively low redox potential, in the system Ac2O-ArCH3-H2SO4-O3 at a temperature of 20 °C has a high substrate selectivity in the reactions of formation of 4-aminobenzyl alcohol. Manganese (II) acetate in the presence of potassium bromide forms a manganese bromide complex with increased catalytic activity, which under the same conditions contributes to the predominant production of 4-aminobenzaldehyde.

Co-disposal of MSWI fly ash and lead–zinc smelting slag through alkali-activation technology

MSWI fly ash and lead–zinc smelting slag (LZSS) are solid wastes containing heavy metals and negatively impact the environment. This study synthesized MSWI fly ash-LZSS based alkali-activated cementitious material (AAFL) material for their co-disposal. The experimental results revealed that the compressive strength of AAFL raised as the SiO2/Na2O molar ratio and alkali content increased but decreased as the liquid–solid ratio and initial curing temperature increased. The immobilization ratios of Zn, Pb and Cu in AAFL were above 97%. Heavy metal speciation, XRD, FTIR, SEM and EDS analysis indicated that the main reaction products were calcium silicate hydrate (C-S-H) and amorphous aluminosilicate gels, and heavy metals were mainly immobilized through physical encapsulation.

Electrooxidation of ethanol and acetaldehyde in neutral electrolyte, an infrared study

• EOR in neutral electrolyte takes place via C1 and C2 pathways. • In situ FTIR reveal the formation of CO adsorbed on the Pt surface at low potentials. • The scission of the C-C bond of ethanol takes place at ca. 300 mv. • Acetic acid is the main reaction product of the EOR or AOR at high potentials. The electrooxidation of ethanol (EOR) in neutral media is attracting a great deal of attention, especially in the area of micro devices and microbial fuel cells. In this work we study the EOR with Pt/C in neutral electrolyte and followed the evolution of the species formed with the potential by in situ FTIR. The EOR in neutral electrolyte displays higher overpotentials than in acid electrolyte but follows a similar reaction pathway, producing mainly C1 species (CO ad , CO 2 ) and C2 species (acetaldehyde, and acetic acid). The scission of the C C bond of ethanol takes place at 200 mV, a potential higher than in acid electrolyte. According to the FTIR experiments, the production of acetaldehyde during the EOR is higher than that of acetic acid. We have also studied the electrooxidation of acetaldehyde (AOR) in a neutral medium with FTIR. We observed the production of CO ad at 300 mV which is oxidized to CO 2 from E ≥ 700 mV.

OXIDATION OF ACETOXITOLUENES WITH MANGAN(III) ACETATE

The kinetics and mechanism of the reaction of ozone with acetoxytoluenes in an acetic anhydride solution in the presence of manganese acetate have been studied. The main reaction products under these conditions are hydroxybenzyl alcohols in the form of the corresponding acetoxybenzyl acetates (65-77%). The effect of manganese (II) acetate on the selectivity of oxidation with respect to the methyl group has been studied. The mechanism of redox catalysis is considered, which explains the obtained experimental data.

Changes in Physicochemical Properties, Volatile Profiles, and Antioxidant Activities of Black Apple During High-Temperature Fermentation Processing.

Black apple is a new elaborated product obtained from whole fresh apple through fermentation at controlled high temperature (60~90°C) and humidity (relative humidity of 50~90%). The appearance, color, texture, and taste of black apple changed dramatically compared with those of fresh apple. In this study, changes in the physicochemical and phytochemical properties, volatile profiles, and antioxidant capacity of apple during the fermentation process were investigated. Results showed that the browning intensity and color difference increased continuously during the whole 65-day fermentation process (p < 0.05). Sugars decreased in the whole fermentation process (p < 0.05), whereas the contents of organic acids increased first and then decreased with prolonged 35 days of fermentation (p < 0.05). Total polyphenol content of black apple showed an increase of 1.5-fold as that of fresh apple, whereas 12 common polyphenolic compounds present in fresh apple decreased dramatically in the whole fermentation process (p < 0.05). The analysis of flavor volatiles showed that high-temperature fermentation decreased the levels of alcohols and esters and resulted in the formation of furanic and pyranic compounds, which are the main products of Maillard reaction (MR). Antioxidant activities of black apple were enhanced compared with those of fresh apple, and results indicated that the enhancement of antioxidant activities was related to the polyphenols and products of MR.

Expression and characterization of a family 45 glycosyl hydrolase from Fomitopsis pinicola and comparison to Phanerochaete chrysosporium Cel45A

To efficiently decompose biomass, fungi have developed various enzymatic and non-enzymatic strategies and are a source of versatile biocatalysts. The endoglucanases in glycosyl hydrolase CAZy family 45 (GH45) are known for their small size, a high thermostability and a broad substrate specificity that has been employed in textile and detergent industries. Here we report the heterologous expression and characterisation of an GH45 endoglucanase from the brown rot Fomitopsis pinicola and its direct comparison to an already characterised GH45 from the white rot Phanerochaete chrysosporium. Both enzymes were recombinantly expressed in Pichia pastoris and purified by two chromatographic steps. The biochemical characterisation highlighted the acidophilic character, with an optimal pH of 4, and a preference for amorphous substrates as carboxymethyl cellulose (CMC) and substrates containing β-1,4-glucans rather than the previously reported β-1,3/1,4-glucans lichenan and β-glucan. The dominating products from β-1,4-glucans were C3–C6 oligosaccharides, whereas from β-1,3/1,4-glucans glucose was the main reaction product. From the characterisation no differences between the brown rot and the white rot GH45 was evident.

Characterization of mechanically activated fly ash-based lightweight geopolymer composite prepared with ultrahigh expanded perlite content

This study focused on the optimization of the production conditions of an ultrahigh expanded perlite lightweight aggregate-filled fly ash-based geopolymer composite and the determination of its product properties. The geopolymer matrix was synthetized using mechanically activated fly ash and an alkaline solution. In a systematic series of experiments, the effect of expanded perlite (EP) content, the compaction pressure and the compaction time on the mechanical properties of the lightweight composite were investigated. In the case of the optimal production conditions, the composites were characterized in terms of physico-mechanical properties, water absorption and microstructure. The composites produced under optimal conditions had an average uniaxial compressive strength of 246 kPa and density of 534 kg/m3 at 80% by volume EP content, and 264 kPa and 221 kg/m3 at 95% by volume EP content. Both the FT-IR spectroscopy and scanning electron microscopy results proved the formation of main geopolymerization reaction products in the matrix of the composite, as well its reaction with the lightweight aggregate.

Catalytic Production of Renewable Hydrogen for Use in Fuel Cells: A Review Study

Hydrogen production from renewable sources is gaining increasing importance for application as fuel, in particular with high efficiency and low impact devices such as fuel cells. In addition, the possibility to produce more sustainable hydrogen for industrial application is also of interest for fundamental industrial processes, such as ammonia and methanol synthesis. Catalytic processes are used in most options for the production of hydrogen from renewable sources. Catalysts are directly involved in the main transformation, as in the case of reforming and of electro-/photo-catalytic water splitting, or in the upgrade and refining of the main reaction products, as in the case of tar reforming. In every case, for the main processes that reached a sufficiently mature development stage, attempts of process design, economic and environmental impact assessment are presented, on one hand to finalise the demonstration of the technology, on the other hand to highlight the challenges and bottlenecks. Selected examples are described, highlighting whenever possible the role of catalysis and the open issues, e.g. for the H2 production from reforming, aqueous phase reforming, biomass pyrolysis and gasification, photo- and electro-catalytic processes, enzymatic catalysis. The case history of hydrogen production from bioethanol for use in fuel cells is detailed from the point of view of process design and techno-economic validation. Examples of steady state or dynamic simulation of a centralised or distributed H2 production unit are presented to demonstrate the feasibility of this technology, that appears as one of the nearest to market. The economic feasibility seems demonstrated when producing hydrogen starting from diluted bioethanol.

3-Aryl-2-azidopropanoic acids in cycloaddition reactions

3-Aryl-2-azidopropanoic acids and their derivatives were studied in the [3+2] and [2+2] cycloaddition reactions. New heterocyclic scaffolds of 3-aryl-2-(1 H -1,2,3-triazol-1-yl)propanoic acids, [1,2,3]triazolo[1,5-a]pyrazin-6(7 H )-one and [1,2,3]triazolo[1,5-a]pyrazine-4,6(5 H ,7 H )-dione were obtained. α-Azidoacids and their derivatives are convenient precursors in the synthesis of drug-like compounds. The azido group can be used as a protected amino group or a precursor of the 1,2,3-triazole ring as a bioisostere to amide moiety. α-Azidoacids are synthetically available and can be easily obtained in diazotransfer reactions from the corresponding α-aminoacids or during the anionic Meerwein arylation of acrylates. In view of this, we decided to investigate them in 1,3-dipolar cycloaddition reactions in order to obtain new compounds for the study of their biological properties. 3-Aryl-2-azidopropanoic acids were investigated in 1,3-dipolar cycloaddition reactions to alkynes. The interaction of acids 1a,b with diethyl ester acetylenedicarboxylic acid 2 under Huisgen cycloaddition (metal free) resulted in the formation of 3-aryl-2-triazolylpropanoic acids 3a,b with good yields. The presence of compounds 3 of carboxyl and ester groups makes them convenient precursors for further heterocyclizations. On the example of 3-aryl-2-triazolylpropanoic acid 3b we have shown the possibility of obtaining [1,2,3]triazolo[1,5- a ] pyrazine rings. The acid 3b was converted by the action of oxalyl chloride to the corresponding acid chloride 4b , the latter in the reaction with isobutylamine under heating led to the formation of a bicyclic derivative 5b . Another synthetic approach to obtaining [1,2,3]triazolo[1,5- a ]pyrazines is the intramolecular cyclization of propargylamides of 2-azidoacids. To implement this approach, we obtained from 3-aryl-2-azidopropanoic acids 1c-f the corresponding propargyl amides 7c-f through intermediate chlorides 6c-f . Reflux of amides 7d,e in toluene for 24 h allowed to obtain the target [1,2,3]triazolo[1,5- a ]pyrazines 8d,e with low yields. We investigated 3-aryl-2-azidopropanoic acid chlorides 6c,f under the conditions of the [2+2]cycloaddition reaction with Schiff bases. However, in contrast to unsubstituted azidoacetic acid chloride, the interaction of acid chlorides 6c , f with Schiff bases 9a,b in the presence of triethylamine as a base at –20 o C did not lead to the formation of azetidinones 10 . The main reaction products were amides 11a,b . Thus, 3-aryl-2-azidopropanoic acids and their derivatives in cycloaddition reactions were investigated. A number of new functionalized 1,2,3-triazole and [1,2,3]triazolo[1,5- a ]pyrazine derivatives were synthesized. The obtained substances can be used for further modifications, and are of considerable interest for medical and pharmaceutical chemistry. Keywords: 3-aryl-2-azidopropanoic acids, alkynes, 1,3-dipolar cycloaddition, 1,2,3-triazoles, [1,2,3]triazolo[1,5- a ]pyrazines.

Reaction of OH radicals with CH3NH2 in the gas phase: experimental (11.7-177.5 K) and computed rate coefficients (10-1000 K).

Nitrogen-bearing molecules, like methylamine (CH3NH2), can be the building blocks of amino acids in the interstellar medium (ISM). At the ultralow temperatures of the ISM, it is important to know its gas-phase reactivity towards interstellar radicals and the products formed. In this work, the kinetics of the OH + CH3NH2 reaction was experimentally and theoretically investigated at low- and high-pressure limits (LPL and HPL) between 10 and 1000 K. Moreover, the CH2NH2 and CH3NH yields were computed in the same temperature range for both pressure regimes. A pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) apparatus was employed to determine the rate coefficient, k(T), in the 11.7-177.5 K range. A drastic increase of k(T) when the temperature is lowered was observed in agreement with theoretical calculations, evaluated by the competitive canonical unified statistical (CCUS) theory, below 300 K in the LPL regime. The same trend was observed in the HPL regime below 350 K, but the theoretical k(T) values were higher than the experimental ones. Above 200 K, the calculated rate coefficients are improved with respect to previous computational studies and are in excellent agreement with the experimental literature data. In the LPL, the formation of CH3NH becomes largely dominant below ca. 100 K. Conversely, in the HPL regime, CH2NH2 is the only product below 100 K, whereas CH3NH becomes dominant at 298 K with a branching ratio similar to the one found in the LPL regime (≈70%). At T > 300 K, both reaction channels are competitive independently of the pressure regime.

Phase transition and equation of state of dense liquid nitrogen at high temperature and high pressure

Nitrogen is the main reaction and detonation product of energetic materials. Therefore, studying the equation of state and phase transition of nitrogen at high temperature and high pressure is very important in evaluating the energy characteristics of energetic materials, especially in designing a new-generation nitrogen-rich energetic materials. Using density functional molecular dynamics simulation method, we calculate the pressure, internal energy and chemical components of fluid nitrogen in a temperature range of 900–25000 K and a pressure range of 2–300 GPa. The negative changes of pressure with temperature on isochores are observed under the temperature and pressure conditions of 3000–10000 K and 20–80 GPa. As the temperature increases, the pressure drop is caused by the collapse of nitrogen molecules. This phenomenon is related to the phase transition from molecular fluid nitrogen to polymerized fluid nitrogen. The triple bond in the molecule breaks and a polymer forms, which is connected by single and double bonds with neighboring atom. We also study the equation of state along Hugoniot curve under impact loading. The obtained Hugoniot curve is in good agreement with the experimental results. It is found that the softening of the experimental curve in a range of 30–60 GPa is related to the decomposition of nitrogen molecules and the formation of polymeric nitrogen.

Interfacial reaction of aluminum borate whisker reinforced Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite

Magnesium matrix composites usually possess high strength and stiffness as well as low coefficient of thermal expansion, which makes them promising in lightweight and energy-saving strategies. Although the interfacial bonding state has a crucial influence on the properties of magnesium matrix composites, the interfacial reaction mechanism of Mg-RE alloy matrix composites is still unclear. Herein, the interfacial reaction and microstructure of Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite reinforced with aluminum borate whisker (Al18B4O33w) were reported by heating the matrix to a semisolid region and inducing the interfacial reaction to continue. After heat treatment at 600 °C for 6 h, the thickness of the interface layer increased from 50‐120 nm to about 335 nm, and the main interfacial reaction product was (Mg0.4Al0.6)Al1.8O4. With the increase of heating time to 12 h, a new double interface layer with (Mg0.4Al0.6)Al1.8O4 in the inner layer and MgO in the outer layer was formed. The difference of interfacial reaction products during isothermal heat treatment was related to the concentration gradient of Mg atoms along the radial direction of the whiskers and the hindrance of the migration of Mg atoms by reaction products formed in the early stage. These findings provide a further understanding of the interfacial reaction of Al18B4O33w reinforced Mg-RE alloy matrix composites.