Nitrosonium Nitrate,an Isomer of N2O4 in IF5

N₂O₄ dissolves in IF₅ as NO⁺NO₃^–, as established by n.m.r spectroscopy, and in the solid state the solvate complex NO⁺NO₃^– · IF₅ is formed. This contains a double chain of alternating NO⁺ cations and NO₃^– anions. (a = 483.4(2), b = 773.9(1), c = 932.6(3) pm, (α = 70.18(2)°, β = 80.90(3)°, (γ = 87.34(2)°, space group P1, Z = 2).     

The reaction of N2O4 with organic compounds

The reaction of N₂O₄ with oximes of formylimidazoles is examined. It is shown that, in addition to the conversion of the oxime group to trinitromethyl, nitration of the imidazole ring occurs including nitration in the 2-position, which is not activated towards electrophilic substitution in acid media.For part VIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 669–673, May, 1970.     

(C5H6N4O)(C5H5N4O)3(C5H4N4O)[Bi2Cl11]Cl2 as a simple and efficient catalyst in Biginelli reaction

A highly efficient and facile procedure for the one‐pot three‐component synthesis of 3,4‐dihydropyrimidin‐2‐(1H )ones/thiones from the one‐pot condensation of aldehyde, β‐dicarbonyl compound and urea/thiourea was developed. The methodology is applicable to a wide range of substrates with high yield in the presence of (C₅H₆N₄O)(C₅H₅N₄O)₃(C₅H₄N₄O)[Bi₂Cl₁₁]Cl₂. The complex is an air‐stable, environmentally friendly and recoverable catalyst and can efficiently catalyze the Biginelli reaction. The catalyst has high catalytic efficiency with low catalyst loading, and can be recycled ten times with only a small loss of activity.     

Initial Studies on the Oxide System Cr2O3–Sb2O4

Differential thermal analysis (DTA) and X-ray diffraction (XRD) were utilized to study the phase equilibrium established in the subsolidus area of the system Cr₂ O₃ –Sb₂ O₄ . It was found that the components of the title system interact in ambient air to produce CrSbO₄ . The compound is stable up to ~1380°C, at which temperature it starts to decompose. This revised version was published online in August 2006 with corrections to the Cover Date.     

Zinc Hydrazides and Alkoxyhydrazides: Organometallic Compounds with Novel Zn4N8, Zn4N6O and Zn4N4O2 Cage Structures

Tetrameric [{RZn(NHNMe₂)}₄] (R = Me, Et), the first organometallic zinc hydrazides to be described, have been prepared by alkane elimination from dialkylzinc solutions and N,N‐dimethylhydrazine. They were characterised by ¹H and ¹³C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X‐ray crystallography. The compounds form asymmetric aggregates containing the novel Zn₄N₈ core; tetrahedra of Zn atoms bear the alkyl groups at Zn, with the triangular faces bridged by NHNMe₂ substituents. The NH groups are connected to two Zn atoms, and the NMe₂ groups to one. Hydrolysis of the compounds with water gives [(RZn)₄(OH)(NHNMe₂)₃] as products, which also were characterised as described above. Higher yields of these hydroxo clusters were achieved in one‐pot syntheses by reaction of dialkylzinc solutions with mixtures of N,N‐dimethylhydrazine and water. They contain Zn₄N₆O cages, in which one hydroxide in the tetrameric hydrazides described above replaces one NHNMe₂ group. Similar products can be prepared with alkoxy instead of hydroxy groups, in analogous one‐pot syntheses with alcohols. Alcoholysis of [EtZn(NHNMe₂)]₄ with methanol or ethanol gave zinc trishydrazide monoalkoxides, [(EtZn)₄(OR)(NHNMe₂)₃] (R = Me, Et), which have constitutions analogous to the monohydroxides. The organozinc bishydrazide bisalkoxides [(MeZn)₄(NHNMe₂)₂(OEt)₂] and [(EtZn)₄(NHNMe₂)₂(OEt)₂] were obtained in one‐pot reactions from dialkylzinc solutions with mixtures of the hydrazine and alcohol, and their crystal structures, confirmed by spectroscopic methods in solution, show an unsymmetrical aggregation with the novel Zn₄N₄O₂ cage structure.     

低热固相反应制备ni0.6cu0.2zn0.2fe2o4纳米晶铁氧体

低热固相反应;溶胶凝胶;nicuzn铁氧体     

Temperature and frequency dependencies of the complex dielectric constant of poly(ethylene oxide) under hydrostatic pressure

Electrical impedance measurements have been made in the frequency range 5 Hz to 10 MHz in pure poly(ethylene oxide) having a molecular weight of 600,000 from 12 K nearly up to the melting point of the crystalline phase (about 330 K). A pronounced relaxation peak in the dielectric loss and a corresponding step in the dielectric constant have been observed at about 240 K, which can be readily related to the glass-rubber transition in the amorphous region of the polymer. As the temperature approaches the melting point there are large increases in the real ϵ′ and imaginary e′ parts of the dielectric constant. The frequency dependence of ϵ′ is characterized by a primary relaxation process, whose frequency increases with increasing temperature as a consequence of decrease of the average structural relaxation time. There is strong evidence that this low-frequency dispersion arises mainly from the diffusive transport of ionic charge carriers rather than a purely orientation relaxation process. In addition, the effects of hydrostatic pressures (0–0.25 GPa) on the frequency dependencies of the real ϵ′ and imaginary ϵ′ parts of the dielectric constant have been measured in the temperature range from 254 to 329 K. An advantage of applying pressure is that it shifts the α_𝒶 relaxation peak into an experimentally accessible frequency window of the equipment; the lowering of frequency results from a decrease in the relaxation volume and a consequent reduction in the mobility of the molecular units. Results are discussed in terms of theoretical models of the effect of pressure on the glass transition, providing information on the cooperative dynamics. © 1996 John Wiley & Sons, Inc.     

Reduction of Aromatic Nitro Compounds under Solvent‐Free Conditions Using Alumina‐Supported Hydrazine/FeNH4(SO4)2·12H2O

Aromatic nitro compounds were easily reduced to the corresponding amino compounds with hydrazine hydrate supported on alumina in the presence of FeNH₄(SO)₂·12H₂O.     

The reaction of selenoaldehydes with 2-methoxyfuran using their generation by retro Diels-Alder reaction

Selenoaldehydes, regenerated by thermal retro Diels-Alder reaction of anthracene cycloadducts under neutral conditions, reacted with 2-methoxyfuran to give methyl penta-2,4-dienoates along with the deposition of elemental selenium. In a similar reaction with 2-methoxyfuran using thioaldehyde, thiirane compound was isolated. This suggests the formation of selenirane intermediates in the above reaction.     

Chemoselective Synthesis of Substituted Imines,Secondary Amines,and β‐Amino Carbonyl Compounds from Nitroaromatics through Cascade Reactions on Gold Catalysts

Substituted imines, α,β‐unsaturated imines, substituted secondary amines, and β‐amino carbonyl compounds have been synthesized by means of new cascade reactions with mono‐ or bifunctional gold‐based solid catalysts under mild reaction conditions. The related synthetic route involves the hydrogenation of a nitroaromatic compound in the presence of a second reactant such as an aldehyde, α,β‐unsaturated carbonyl compound, or alkyne, which circumvents an ex situ reduction process for producing the aromatic amine. The process is shown to be highly selective towards other competing groups, such as double bonds, carbonyls, halogens, nitriles, or cinnamates, and thereby allows the synthesis of different substituted nitrogenated compounds. For the preparation of imines, substituted anilines are formed and condensed in situ with aldehydes to provide the final product through two tandem reactions. High chemoselectivity is observed, for instance, when double bonds or halides are present within the reactants. In addition, we show that the Au/TiO₂ system is also able to catalyze the chemoselective hydrogenation of imines, so that secondary amines can be prepared directly through a three‐step cascade reaction by starting from nitroaromatic compounds and aldehydes. On the other hand, Au/TiO₂ can also be used as a bifunctional catalyst to obtain substituted β‐amino carbonyl compounds from nitroaromatics and α,β‐unsaturated carbonyl compounds. Whereas gold sites promote the in situ formation of anilines, the intrinsic acidity of Ti species on the support surface accelerates the subsequent Michael addition. Finally, two gold‐catalyzed reactions, that is, the hydrogenation of nitro groups and a hydroamination, have been coupled to synthesize additional substituted imines from nitroaromatic compounds and alkynes.     

Vanadyl phosphate dihydrate,a solid acid: the role of water in VOPO4·2H2O and its sodium derivatives Na x (VIV x VV 1−x O)PO4·(2−x)H2O

Sodium-containing intercalates having as general formula Na _x VOPOP₄·(2–x)H₂O (0.25x<0.50) have been obtained and characterized. Orthorhombic phases, which essentially maintain the structure of the layered oxide hydrate VOPO₄·2H₂O result. Intercalated sodium ions act as pillars. The presence of H₃O⁺ ions in the parent VOPO₄·2H₂O and also in some reduced phases, is detected. The understanding of the structural role of the water molecules is advanced and the topotactic dehydration/rehydration processes are studied. The formation of a new metastable VOPO₄·H₂O phase is established.     

加压下氢气对煤焦水蒸气气化反应的影响

在加压固定床微分反应器上对霍林河褐煤焦(HLH)、神木烟煤焦(SM)和晋城无烟煤焦(JC)与水蒸气/氢气混合气的加压气化反应特性进行了研究。结果表明,氢气对煤焦水蒸气气化反应具有明显的抑制作用,其抑制作用大小分别随氢气分压、总压和煤阶的提高而增强,而随反应温度升高而减弱;有氢气存在和无氢气存在时煤焦水蒸气气化反应过程都能用相同的动力学模型描述,有氢气存在时煤焦水蒸气气化的最终碳转化率低于纯水蒸气气化的最终碳转化率;氢气对煤焦水蒸气气化反应的抑制机理与氢气的分压范围有关,当氢气分压很低时,氢气的抑制作用主要是由于氢气离解生成的氢原子占据煤焦表面活性位所致,而当氢气分压很高时,氢气的抑制作用主要是由于氧交换反应的逆反应加强所致。     

The effect of N2O4 on the crystalline structure of cellulose

Depending on reaction conditions, the system cellulose–N₂O₄ may give two different unstable crystalline compounds, one being an ester (cellulose trinitrite), the second, an adduct of cellulose and HNO₃ (the Knecht compound). For these compounds, mechanisms of the formation of the crystalline phase as a result of topochemical reaction and self-organization are discussed. The different characteristics of structural transformations of the fiber under nitrosation and nitration are noted. The existence of polymorphic forms of the Knecht compound is suggested. These labile nitrogen-containing compounds make possible the regeneration of cellulose in its various modifications (cellulose I, II, IV, or amorphous cellulose) from the cellulose–N₂O₄ system. The formation of unstable compounds and their ability to crystallize in the reaction medium allows the passage from amorphous cellulose to its crystalline modifications II or IV under mild conditions. The causes of decrystallization of cellulose by N₂O₄ are established. © 1993 John Wiley & Sons, Inc.