Temperature dependence of the reaction NO + NO3 → 2NO2

The flash photolysis-visible absorption technique has been used to measure rate constants for the reaction NO + NO₃ → 2NO₂ (1) over the temperature range 224–328 K. The temperature dependence of the rate constant is given by the expression k₁(T) = (1.59 ± 0.32) × 10⁻¹¹exp(122/T) cm³ molecule⁻¹ s⁻¹ where the stated uncertainties refer to the ± 2σ limits from both random and systematic errors.     

Preparation and Properties of MoO3−TiO2−SiO2 Composites with Spherical Shape of Agglomerates

Russian Journal of Applied Chemistry - MoO3?TiO2?SiO2 composites with spherical shape of agglomerates were prepared by thermal decomposition of TOKEM-400 and TOKEM-840 anion-exchange...     

Reaction products and kinetics of the reaction of NO2 with γ-Fe2O3

The reaction of NO(2) with Fe(2)O(3) has relevance for both atmospheric chemistry and catalysis. Most studies have focused on hematite, α-Fe(2)O(3), as it is the thermodynamic stable state of iron oxide; however, other forms of Fe(2)O(3) naturally occur and may have different chemistries. In this study, we have investigated the reaction products and kinetics for NO(2) reacting with γ-Fe(2)O(3) powder using diffuse reflectance infrared Fourier transform spectroscopy and compared the results to those of previous studies of NO(2) reacting with α-Fe(2)O(3). Both α- and γ-Fe(2)O(3) produce surface-bound nitrate at the pressures examined in this study (24-212 mTorr); surface-bound nitrite products are observed at all pressures for γ-Fe(2)O(3) whereas nitrite was only observed on α-Fe(2)O(3) at lower pressures. Surface-bound NO(+) and Fe-NO products are observed on γ-Fe(2)O(3), which have not been observed with α-Fe(2)O(3). The reaction kinetics show a first-order dependence on NO(2) pressure and this is used to support the hypothesis of unimolecular reaction of adsorbed NO(2) with the γ-Fe(2)O(3) surface as the slow step in the reaction mechanism. The difference in product formation between NO(2) reacting with γ-Fe(2)O(3) and previous studies of α-Fe(2)O(3) illustrate the fact that care must be taken in generalizing reactivity of different polymorphs.     

Preparation of natural isovaleraldehyde by the Maillard reaction

Isovaleraldehyde possesses malty,fruity,cocoa-like odor and is widely used in fruit,chocolate,coffee flavors.The preparation of natural isovaleraldehyde by the Maillard model reaction was studied in this paper.The effects of the ratio of D-glucose/L-leucine, reaction temperature and pH value on the yield of isovaleraldehyde were explored.The optimum conditions were as follows: n(D-glucose):n(L-leucine)=4,temperature 150℃,reaction time 3 h,pH 5.The highest yield of isovaleraldehyde obtained was about 32%.     

Preparation of PMMA Foam by Supercritical CO_2 with Ethanol

Supercritical (SC) CO2 can plasticize many amorphous polymers, which reduce the glass transition temperature of the polymers significantly. Recently, it was used as blowing agent to foam amorphous materials such as poly(methyl methacrylate) (PMMA)1,2, polystyrene (PS)3, polycarbonate (PC)4 and poly(ethylene terephthalate) (PET)4. In this foaming process, a polymer is saturated with SC CO2, and followed by rapid depressurization to atmospheric pressure. The microcellular foams can be ob…     

One-pot synthesis of borolanes by reaction of aluminacyclopentanes with BF3·Et2O

A selective procedure was developed for the synthesis of substituted borolanes via transmetalation with BF₃ · Et₂O of 3-alkyl-1-ethylaluminacyclopentanes obtained from the corresponding terminal olefins and AlEt₃ in the presence of Cp₂ZrCl₂ as a catalyst. 3-Substituted 1-fluoroborolanes were isolated and identified as 1: 1 complexes with EtBF₂.     

Synthesis of substituted pyrrolidines by reaction of aryl-substituted vinylidenecyclopropanes with aromatic imines catalyzed by BF3·Et2O

The reactions of 1,1-diaryl-2-(diphenylvinylidene)cyclopropanes and 1,1-diaryl-2-(2-phenylpropenylidine) cyclopropanes with aromatic amines in the presence of BF₃·Et₂O leads to the formation of pyrrolidine derivatives. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 552–557, April, 2008.     

Synthesis of 2-arylpyrrolidines by reaction of γ-ureidoacetals with benzene-1,3,5-triol

New 2,2′-(2,4,6-trihydroxybenzene-1,3-diyl)dipyrrolidine derivatives have been synthesized by reaction of benzene-1,3,5-triol (phloroglucinol) with γ-ureidoacetals in the presence of trifluoroacetic acid as catalyst.     

Theoretical study on the mechanism of C2Cl3 + NO2 reaction

The radical-molecule reaction of C₂Cl₃ with NO₂ is explored at the B3LYP/6-311G(d,p) and CCSD(T)/6-311+G(d,p) (single-point) levels. On the singlet potential energy surface (PES), the association between C₂Cl₃ and NO₂ is found to be carbon-to-nitrogen attack forming the adduct C₂Cl₃NO₂ (1) without any encounter barrier, followed by isomerization to C₂Cl₃ONO (2). Starting from 2, the most feasible pathway is the N–O1 bond cleavage which lead to P ₁ (C₂Cl₃O + NO). Much less competitively, 2 transforms to the three-membered ring isomer c-OCCl₂C–ClNO (4 ^a ) which can easily interconvert to c-OCCl₂C–ClNO 4 ^b . Then 4 (4 ^a , 4 ^b ) takes direct C1–C2 and C2–O1 bonds cleavage to give P ₂ (COCl₂ + ClCNO). The lesser competitive channel is the 4 ^a isomerizes to the four-membered ring intermediate O-c-CNClOCCl₂ (5) followed by dissociation to P₃ (CO + ClNOCCl₂). The concerted 1,2-Cl shift along with C1–O1 bond rupture of 4 ^b to form ONC(O)CCl₃ (6) followed by dissociation to P ₄ (ClNO + OCCCl₂) is even much less feasible. Moreover, some of P ₃ and P ₄ can further dissociate to P ₅ (ClNO + CO + CCl₂). Compared with the singlet pathways, the triplet pathways may have less contribution to the title reaction. Our results are in marked difference from previous theoretical studies which showed that two initial adducts C₂Cl₃–NO₂ and C₂Cl₃–ONO are obtained. Moreover, in the present paper we focus our main attentions on the cyclic isomers in view of only the chain-like isomers are considered by previous studies. The present study may be helpful for understanding the halogenated vinyl chemistry.     

Synthesis of 3-substituted indole by AlCl3-promoted reaction of β,γ-unsaturated ketone with indole

A one-pot Lewis acid-promoted reaction condition of β,γ-unsaturated ketone with indole was developed for the synthesis of 3-substituted indoles with moderate to good yields. A Lewis acid such as AlCl₃ was shown to be a promising promoter for in situ isomerization of β,γ-unsaturated ketone to its corresponding α,β-unsaturated ketone, then undergoing Friedel–Crafts Michael addition reaction with indole to afford 3-substituted indole.     

17O excess transfer during the NO2 + O3 → NO3 + O2 reaction

The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)?) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen.     

Preparation of CuCrO2 nanoparticles with narrow size distribution by sol–gel method

Copper chromium oxide (CuCrO₂) nanoparticles were synthesized by sol–gel method. The effect of annealing temperature, duration of heat treatment and metallic ion concentration in precursor solution on the structural properties of the nanoparticles was investigated. The delafossite structure of CuCrO₂ powder was confirmed by X-ray diffractometer. It was found that the crystallite sizes as well as the size of the nanoparticles increased with annealing temperature and duration of heat treatment but decreased with metallic ion concentration. Nanoparticles’ size was obtained using particle size analyzer. The synthesized CuCrO₂ nanoparticles with 0.7 M metallic ion concentration have the lowest crystallite and particle sizes with a narrow size distribution in the range of 13.5–15.6 nm. In the presence of this metallic ion concentration, we could also produce single crystal CuCrO₂ nanoparticles. Moreover, the CuCrO₂ nanoparticles exhibit a large optical band gap that increases with metallic ion concentration. The optical band gap of the nanoparticles fabricated with 0.7 M metallic ion concentration in precursor solution is about 3.99 eV.     

Theoretical study on the reaction mechanism of (CH_3)_3CO~· radical with NO

Alkoxy radicals RO? form an important class of hydrocarbon oxidation intermediates in combustion processes, interstellar and atmospheric chemistry[1—8]. The number of NO to NO2 conversions can take place during the oxidation of the parent hydrocarbon in the atmosphere and hence affecting tropospheric ozone production. The experimental and theoretical investi-gations of the reactions of alkoxy radicals will be ad-vantageous for safeguarding the environment. Despite the importance of alkoxy r…     

Preparation and formation process of Ni2+–Fe3+ CO32− LDHs materials with high crystallinity and well-defined hexagonal shapes

A new complexing agent assisted homogeneous precipitation technology was successfully developed to synthesize Ni²⁺–Fe³⁺ CO₃^2? LDHs materials with crystallinity and well-defined hexagonal shape [1]. By using urea as hydrolysis agent and trisodium citrate as complexing agent, Ni²⁺–Fe³⁺ CO₃^2? LDHs with different ratios of Ni²⁺/Fe³⁺ were prepared under optimized reaction conditions, and their formation process was discussed on the basis of the experimental results. Ni²⁺–Fe³⁺ CO₃^2? LDHs thin hexagonal nanoplates with high crystallinity were obtained for from the ratios of Ni²⁺/Fe³⁺ = 3 and 4, while Ni²⁺–Fe³⁺ CO₃^2? LDHs material from Ni²⁺/Fe³⁺ = 2 could not be obtained due to the formation of impurity β-Ni(OH)₂. The as-prepared Ni²⁺–Fe³⁺ CO₃^2? LDHs materials were completely converted to Cl^? LDHs materials by treating with a NaCl–HCl mixed solution, showing a good anion exchange property. Sodium fluoride, tartarate and trisodium citrate with different molecular structures were chosen as a complexing agent to investigate their effect on the crystalline and shape of the as-prepared materials. Not only had the molecular structure of the complexing agents but also the amount had an obvious effect in the formation of the as-prepared materials. Trisodium citrate played a key role for the formation of Ni²⁺–Fe³⁺ CO₃^2? LDHs materials with high crystalline and well-defined hexagonal shapes, which made the pH deposition range of Fe(OH)₃ increase due to the formation of metal ligand [Fe(C₆H₄O₇)₂]^5? when the pH of the reaction system was above 8. The formed metal ligand [Fe(C₆H₄O₇)₂]^5? changed the translation process of Fe(OH)₃ with Ni²⁺ ions, which reacted with free Ni²⁺ ions and formed Ni²⁺–Fe³⁺ CO₃^2? LDHs materials with high crystallinity and well-defined hexagonal shapes.     

Collisional quenching of NO(B2Πr)υ′ = 0 produced by the reaction of N(2D) with N2O

The reaction of N(²D) with N₂O has been used as a source of NO(B²Π_r)υ′= 0. The effects of added gases on its emission have been used to determine quenching rate coefficients (using a radiative lifetime of 3 × 10⁻⁶ s). These coefficients have been compared with rate coefficients for quenching the isoenergetic species NO(A²Σ⁺)υ′= 0,1.     

A new route of the reaction of EtAlCl2 with α-olefins catalyzed by Ti complexes

A new method for the synthesis of dialkyl(ethyl)alanes by the reaction of EtAlCl₂ with -olefins in the presence of Mg and a catalytic amount of Cp₂TiCl₂ (Ti(OPrⁱ)₄, Ti(OBuⁿ)₄) in THF was developed.     

An unusual new reaction of α-olefins with magnesiumn-alkyl derivatives catalyzed by Cp2ZrCl2

The reaction of organomagnesium compounds (OMC) containing alkyl radicals of normal structure with -olefins, resulting in the formation of alkenylorganomagnesium compounds and accompanied by hydride transfer was discovered and systematically investigated. A scheme providing for the formation of zirconacyclopentane complexes was proposed for the mechanism of the reaction.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1187–1196, May, 1992.     

The reaction of β-lactam carbenes with 3,6-dipyridyltetrazines: switch of reaction pathways by 2-pyridyl and 4-pyridyl substituents of tetrazines

The reactions of β-lactam carbenes with both 3,6-di(2-pyridyl)tetrazine and 3,6-di(4-pyridyl)tetrazine were studied. It was found that β-lactam carbenes reacted with 3,6-di(2-pyridyl)tetrazine to produce 5-triazolo[1,5-a]pyridylpyrrol-2-ones in good yields, while with 3,6-di(4-pyridyl)tetrazine, they afforded pyrido[c]cyclopenta[b]pyrrol-2-ones in moderate yields. Both reactions were proposed to follow cascade mechanisms containing a 3,6a-dipyridylpyrrolo[3,2-c]pyrazol-5-one intermediate. The different pathways of the transformation of pyrrolo[3,2-c]pyrazol-5-ones were switched by the 2- and 4-pyridyl substituents. This work not only provided a simple and efficient strategy for the construction of novel triazolo[1,5-a]pyridine and pyrido[c]cyclopenta[b]pyrrole derivatives, respectively, but also revealed two different thermal transformation patterns of 3H-pyrazole compounds.     

Study of the reduction of MoO3γAl2O3 and WO3γAl2O3 catalysts by laser raman spectroscopy

Various pretreatements on those catalysts (oxide form) followed by H₂ reduction show that the primary effect of H₂ is a dehydration reaction. At high Mo loading, Two consecutive steps of reduction are evidenced: (i) formation of Mo (V) species as Mo(V)OH and (ii) formation of Mo(IV) species characterized by a

(X =V, IV) bridge whose stretching mode is about 760 cm⁻¹. Low Mo loading samples are more difficult to reduce. By comparison with the Mo catalysts, the Wo₃γAl₂O₃ samples are less easily reducible but a similar initial reduced state has been found.