Direct functionalization of 4,5-dichloropyridazin-6-one

Direct functionalization of 4,5-dichloropyridazin-6-one with some nucleophiles in seven solvents gave regioselectively 5-halo-4-substituted-pyridazin-6-ones as main product. Reaction of 4,5-dichloropyridazin-6-one with 2-mercaptopyrimidine (2 equivalents) also afforded 4,5-di(pyrimidin-2-ylsulfanyl)pyridazin-6-one as the main product.     

Understanding in-cylinder soot reduction in the use of high pressure fuel injection in a small-bore diesel engine

This study shows how soot particles inside the cylinder of the engine are reduced due to high pressure fuel injection used in a light-duty single-cylinder optical diesel engine fuelled with methyl decanoate, a selected surrogate fuel for the diagnostics. For various injection pressures, planar laser induced incandescence (PLII) imaging and planar laser-induced fluorescence of hydroxyl (OH-PLIF) imaging were performed to understand the temporal and spatial development of soot and high-temperature flames. In addition, a thermophoresis-based particle sampling technique was used to obtain transmission electron microscope (TEM) images of soot aggregates and primary particles for detailed morphology analysis. The OH-PLIF images suggest that an increase in the injection pressure leads to wider distribution of high-temperature flames likely due to better mixing. The enhanced high-temperature reaction can promote soot formation evidenced by both a faster increase of LII signals and larger soot aggregates on the TEM images. However, the increased OH radicals at higher injection pressure accelerates the soot oxidation as shown in a higher decreasing rate of LII signals as well as dramatic reduction of the sampled soot aggregates at later crank angles. The analysis of nanoscale carbon layer fringe structures also shows a consistent trend that, at higher injection pressure, the soot particles are more oxidized to form more graphitic carbon layer structures. Therefore, it is concluded that the in-cylinder soot reduction at higher injection pressure conditions is due to enhanced soot oxidation despite increased soot formation.     

In-flame soot particle structure on the up- and down-swirl side of a wall-interacting jet in a small-bore diesel engine

This study shows how the structure of soot particles within the flame changes due to the relative direction of the swirl flow in a small-bore diesel engine in which significant flame–wall interactions cause about half of the flame travelling against the swirl flow while the other half penetrating in the same direction. The thermophoresis-based particle sampling method was used to collect soot from three different in-flame locations including the flame–wall impingement point near the jet axis and the two 60° off-axis locations on the up-swirl and down-swirl side of the wall-interacting jet. The sampled soot particle images were obtained using transmission electron microscopes and the image post-processing was conducted for statistical analysis of size distribution of soot primary particles and aggregates, fractal dimension, and sub-nanoscale parameters such as the carbon layer fringe length, tortuosity, and spacing. The results show that the jet-wall impingement region is dominated by many small immature particles with amorphous internal structure, which is very different to large, fractal-like soot aggregates sampled from 60° downstream location on the down-swirl side. This structure variation suggests that the small immature particles underwent surface growth, coagulation and aggregation as they travelled along the piston-bowl wall. During this soot growth, the particle internal structure exhibits the transformation from amorphous carbon segments to a typical core–shell structure. Compared to those on the down-swirl side, the soot particles sampled on the up-swirl side show much lower number counts and more compact aggregates composed of highly concentrated primary particles. This soot aggregate structure, together with much narrower carbon layer gap, indicates higher level of soot oxidation on the up-swirl side of the jet.     

Polymorphic phase transition and thermal stability in squaric acid (H2C4O4)

Phase transformations in squaric acid (H₂C₄O₄) have been investigated by thermogravimetry and differential scanning calorimetry with different heating rates β. The mass loss in TG apparently begins at onset temperatures T_di=245±5 °C (β=5 °C min^?1), 262±5 °C (β=10 °C min^?1), and 275±5 °C (β=20 °C min^?1). A polymorphic phase transition was recognized as a weak endothermic peak in DSC around 101 °C (T_c⁺). Further heating with β=10 °C min^?1 in DSC revealed deviation of the baseline around 310 °C (T_i), and a large unusual exothermic peak around 355 °C (T_p), which are interpreted as an onset and a peak temperature of thermal decomposition, respectively. The activation energy of the thermal decomposition was obtained by employing relevant models. Thermal decomposition was recognized as a carbonization process, resulting in amorphous carbon.     

Simulation of radioactivation and chlorination reaction behavior for Zircaloy-4 and Zirlo cladding hull wastes

Radioactivation of Zircaloy-4 (Zry-4) and Zirlo cladding hulls after 55 GWD/tU burn-up and 10 years of cooling was simulated using the ORIGEN-S code. The simulation results revealed that ¹²⁵Sb and ⁶⁰Co are major contributors of both radioactivity and decay heat in the case of the Zry-4 hulls. For the Zirlo hulls, ^93mNb and ¹²⁵Sb consisted 82.2% of radioactivity while ¹²⁵Sb and ⁶⁰Co emitted 77.9% of decay heat. Although the radioactivity between the Zry-4 (1.17 Ci for 1 kg of fresh Zry-4) and Zirlo (1.38 Ci for 1 kg of fresh Zirlo) hulls was not significantly different, decay heat of the activated Zry-4 hulls (8.58 mW) was much larger than 1.62 mW of the activated Zirlo hulls. This gap might have come from the different major constituents of Zry-4 (Zr, Sn, Fe, and Cr) and Zirlo (Zr, Sn, Nb, and Fe) resulting in different radioactive nuclides after radioactivation. Chlorination reaction behavior of the activated Zry-4 and Zirlo hulls was performed using the HSC chemistry code. Constituents of recovered ZrCl₄ were investigated via changes of Gibbs free energy and boiling points of resulting chlorides. The calculation results suggested that radioactivity and decay heat might decrease by 49.0 and 81.8%, respectively, in the ZrCl₄ recovered from the activated Zry-4 hulls. In the case of Zirlo, it was expected that radioactivity and decay heat might decrease by 11.6 and 13.0%, respectively, after the chlorination reaction. Effect of cooling time on radioactivity and decay heat was also investigated.     

Chemoselective synthesis of 1-alkyl-4-(4-amino-2,6-dichlorophenoxy)-5-halopyridazin-6-ones

Some 1-alkyl-4-(4-amino-2,6-dichlorophenoxy)-5-halopyridazin-6-ones were synthesized chemoselectively from 1-alkyl-4,5-dihalopyridazin-6-ones and 4-amino-2,6-dichlorophenol via a fluoride ion-assisted reaction.     

1H nuclear magnetic resonance study of mixed-valent dodecylamine-intercalated vanadium oxide nanosheets

Alkyl-chain dynamics in the mixed-valent dodecylamine-intercalated vanadium oxide nanosheets (C12VONS) was investigated by means of 400-MHz ¹H nuclear magnetic resonance. Two C12VONS samples with distinct alkylammonium-to-alkylamine ratios showed distinct alkyl-chain dynamics, the alkylammonium chains being apparently more disordered than the alkylamine chains. The high-temperature spin–lattice relaxation is dominated by the conformational chain defects and the reorientational motions of the alkyl chains, respectively, in the alkylammonium-abundant system and in the alkylamine-abundant system. The reorientational and conformational changes of the alkyl chains appear to be uncorrelated with the magnetic transitions.     

Study on the Constituents of Roots of Aceriphyllum rossii

A new stereoisomer of a tetrahydrofuranoid lignan, acerifuranoid A ( 1 ), and two new oleanane‐type triterpenoids, aceriphyllic acids J and K ( 2 and 3 ), were isolated from the roots of Aceriphyllum rossii. Their structures were elucidated on the basis of spectroscopic analyses and chemical evidence. These isolated compounds exhibited weak cytotoxic activity against various cancer cell lines with IC₅₀>150 μM .     

Development of a multiresidue method for the determination of multiclass pesticides in soil using GC

The principal objective of the present study was to develop a multiresidue analytical method for 62 pesticides in a soil matrix. Soil samples were fortified with known quantities of pesticides at two different concentration levels (0.1 and 0.01 μg/g) and the analytes were extracted via a liquid–solid extraction method. The pesticides were separated on an HP5 capillary column and were detected by gas chromatography coupled to an electron capture detector (GC‐ECD). The method was validated, considering its good linearities (r² = 0.978–0.999), specificity and recovery characteristics. Recoveries were found between 70.3 and 113.4% for all pesticides except edifenphos (67.5%) and dichlobenil (69.5%) spiked at a 0.1 μg/mL concentration level and 74.5–117% except ethalfluralin (63.3%) and dichlobenil (51.9%) spiked at a concentration of 0.01 μg/mL. The developed method could be utilized as a simple and cost‐effective method for the routine analysis of 62 pesticides in soil samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Expeditious syntheses of conjugated allenyl esters and oxazoles through a cascade reaction of alpha-alkynyl malonates under alkaline conditions

Diethyl alpha-alkynyl-alpha-methoxymalonates (2a--e) were smoothly hydrolyzed and then decarboxylated under alkaline conditions employing 1 N KOH in EtOH to give conjugated allenyl esters (6a--e) in high yields, and similar alkaline treatment of diethyl alpha-alkynyl-alpha-acetylaminomalonates (5a, b, d, e) furnished unexpectedly the oxazoles (7a, b, d, e) having three substituent groups in excellent yields.