A new strategy for the synthesis of α,β-diaroylpropionates promoted by samarium metal in DMF

When promoted by samarium in DMF, aroyl chlorides react readily with acrylates to afford α,β-diaroylpropionates in good to excellent yields without pretreating or activating the metallic samarium.     

Thermal Analysis of Acrylonitrile Polymerization and Cyclization in the Presence of N,N-Dimethylformamide

This paper examines the polymerization of acrylonitrile to poly(acrylonitrile)(PAN), and its cyclization, in bulk form and using N,N-dimethylformamide (DMF) as solvent in which both monomer and polymer are soluble. Thermal analysis of the resultant products after polymerization has been performed by DSC and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Scanning electron microscopy has been used to study the morphology of the resultant products and after thermal treatments. The DSC thermal curve of PAN-DMF sample is quite different from the PAN bulk sample, showing a single sharp exothermic peak associated with nitrile group polymerization (cyclization) of PAN at lower temperature (240°C) than that of bulk PAN sample (314°C). Cyclization of PAN was confirmed by IR spectroscopy. It was found that the amide molecules are difficult to eliminate completely in the product obtained after the polymerization reaction, even after prolonged heating at 110°C, and remain occluded. The formation of a complex by dipolar bonding is also possible and it is discussed. It is concluded that the amount of heat evolved as well as the temperature interval over which it is released are influenced by the chemical processing of PAN when using DMF as solvent of both monomer and polymer. Pyrolysis of these PAN samples revealed the release of occluded molecules of DMF, and several compounds containing nitrogen produced from the thermal degradation processes. All these results are interesting to know the chemical processing of carbon fibres and activated carbon fibres from PAN modified precursors.This revised version was published online in November 2005 with corrections to the Cover Date.     

簇合物[Fe（DMF）6][W2S6]的合成,结构和性能研究

以(NH_4)_2WS_4、FeCl_3和NaS_2CNC_5H_(10)为原料,合成出[Fe(DMF)_6][W_2S_6]簇合物,用X射线衍射法测定了晶胞结构.其晶胞参数为a=0.8778(1)nm,b=0.9467(3)nm,c=1.1362(6)nm,α=71.506(1)°,β=74.775(2)°,γ=74.775(2)°,ν=0.84806nm~3,Z=1.晶体结构经块矩阵最小二乘法精修后,最终偏离因子R=0.0811.此外还进行了红外光谱、紫外可见光谱的测定.     

NMR and Excess Volumes Studies in DMF–Alcohol Mixtures

Chemical shifts of the alcohol and DMF protons in DMF–alcohol mixtures with the mole fraction of alcohol are reported in order to study the hydrogen bond interaction present in the mixtures. The densities of DMF–methanol mixture at 22°C are also measured. Excess volumes and excess chemical shifts are correlated by the Redlich–Kister equation. The relation between excess volumes and excess chemical shifts in the mixtures is discussed. It is found that the maximum excess chemical shifts ^E(CHO-OH) and ^E(CH₃-OH) are positioned at about mole fraction methanol = 0.57 for the DMF–methanol system, as is V ^E. The results show that the NMR spectral method offers a valuable approach to similar future studies of interactions in mixtures.     

Determination of ammonia based on the electro-oxidation of hydroquinone in dimethylformamide or in the room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

The results detail a novel methodology for the electrochemical determination of ammonia based on its interaction with hydroquinone in DMF. It has been shown that ammonia reversibly removes protons from the hydroquinone molecules, thus facilitating the oxidative process with the emergence of a new wave at less positive potentials. The analytical utility of the proposed methodology has been examined with a linear range from 10 to 95 ppm and corresponding limit-of-detection of 4.2 ppm achievable. Finally, the response of hydroquinone in the presence of ammonia has been examined in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide, [EMIM][N(Tf)₂]. Analogous voltammetric waveshapes to that observed in DMF were obtained, thereby confirming the viability of the method in either DMF or [EMIM][N(Tf)₂] as solvent.     

第五丶六族元素的有机化合物在有机合成中应用的研究 XXIII. 卤化烷氧羰基烷基三苯基 在N,N-二甲基甲酰胺中的分解反应

本文报道卤化烷氧羰基烷基三苯基在N,N-二甲基甲酰胺中, 100°C左右加热时所发生的分解反应. 当盐1的酯烷基R2 为甲基国, 生成产物为 有时也生成2和3的混合物. 当 盐1的酯烷基R2为乙基或正戊基时, 只生成产物2.     

Studies of transformations of 4-X-2,3,5,6-tetrafluoro-2′-aminosubstituted diphenyl ethers in DMF

The rate of cyclization of pentafluoro- (1) and 4-Cl-2,3,5,6-tetrafluoro-2-NHY-diphenyl ethers (2a, Y=Ac;2b, Y=H;2c, Y=Me) to form phenoxazines on refluxing in DMF increases with an increase in the nucleophilicity of the amino group. The cyclization of the N-acetyl derivative2a is followed by the Smiles rearrangement, whereas the transformation of ethers2b andc, containing free amino and N-methylamino groups, respectively, includes mainly an attack on the amino group at theortho-position of the fluorinated ring. In the case of ether2c, introduction of K₂CO₃ into the reaction mixture results in cyclization with the Smiles rearrangement.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1101–1105, June, 1993.     

Structure and stability of hydrogen fluoride complexes with N,N-dimethylformamide

The structure, stability, and paths of formation of 11 (HF)_m(DMF)_n heterocomplexes (m = 1–4, n = 1, 2) were studied in terms of the B3LYP/6-31++G(d, p) density functional calculation. The results of this calculation suggest that: a) addition of hydrogen fluoride molecules to the (HF)_mDMF cyclic fragment is the basic tendency in complex formation in the HF-DMF system; b) data about the structure and properties of stable molecular forms that prevail in N,N-dimethylformamide solutions of hydrogen fluoride can be obtained by quantum chemical calculations for (HF)_mDMF complexes (m = 5–10).     

多氟芳烃的亲核反应I.仲胺作为亲核试剂

本文报道全氟苯、一氯五氟苯和二氯四氟苯与仲胺在DMF或HMPA中的亲核反应结果,C6F5Cl与仲胺反应生成对位产物,C6F4Cl2(m:o:p)=73:18:9)与仲胺的反应,只有m-和o-异构体能生成预期产物,而p-C6F4Cl2只与活性高的四氢吡咯反应,延长反应时间和提高反应温度,C6F6可给出对双取代产物,六个仲胺的反应活性顺序是:四氢吡咯>哌啶>吗啡啉>二乙胺>二正丙胺>二异丙胺。