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71.
Mohammad M. Mojtahedi M. Saeed Abaee Mashal Javadpour 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2362-2365
Solvent-free protection of aromatic and aliphatic thiols with acetic anhydride was performed at room temperature under trace quantities of magnesium bromide ethyl etherate, affording rapid formation of various thiol esters in excellent yields. 相似文献
72.
Toshio Matsuda Yoshiyuki Takada 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):75-79
Abstract In a previous paper,1 we reported the formation of a resinous material (1) from the reaction of sulfur chloride with acetophenone which, upon treatment with DMF, yielded phenylglyoxylthiodimethylamide (4). We now report two additional resinous materials (5, 6), resulting from bromination of sodium phenacylthiosulfate (3) and diphenacyl disulfide (7) respectively, both of which not only resemble resinous 1 in appearance, but also yield 4 upon treatment with DMF in aqueous alkali. Resinous 1, 5, and 6 appear to have the same common basic structure and differ only in the number of sulfur atoms bonded between the common units. Cleavage at the sulfur-sulfur bonds and elimination of hydrogen halide then yields identical oxothioamides from 1, 5, or 6. The latter appears to be a general reaction, and several oxothioamides were prepared by this synthetic method from 1, 5, and 6 and various amides and amines. 相似文献
73.
The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP. 相似文献
74.
Monzer Fanun 《Journal of Dispersion Science and Technology》2013,34(8):1244-1253
In this work, we studied the phase behavior as function of temperature of water/sucrose stearate/propylene glycol/oil and water/sucrose stearate/ethoxylated mono‐di‐glyceride/oil systems. The oils were R (+)‐limonene, isopropylmyristate, and caprylic‐capric triglyceride. It was found that adding propylene glycol and ethoxylated mono‐di‐glyceride to the water/sucrose stearate/R (+)‐limonene and water/sucrose stearate/isopropylmyristate systems decreases the temperature and surfactants concentration needed for the formation of a microemulsion phase region and no three phase region is observed. In the case of water/sucrose stearate/caprylic‐capric triglyceride system a three phase region is observed. In the caprylic‐capric based system, it was found that increasing the propylene glycol and ethoxylated mono‐di‐glyceride contents decrease the phase inversion temperature and increases the efficiency. In the case where the mixed surfactants (sucrose stearate and ethoxylated mono‐di‐glyceride) were present in the system, the efficiencies observed are higher than those observed in the system based on the mixture of sucrose stearate and propylene glycol. 相似文献
75.
Junling Bai Toshifumi Nakatani Yuuki Sasaki Sadanobu Inoue Nobuo Takahashi 《International journal of environmental analytical chemistry》2013,93(9):856-865
Effectiveness of Pd/Mg chemical modifier for the accurate direct determination of zinc in marine/lacustrine sediments by graphite furnace atomic absorption spectrometry (GF-AAS) using slurry samples was evaluated. A calibration curve prepared by aqueous zinc standard solution with addition of Pd/Mg chemical modifier is used to determine the zinc concentration in the sediment. The accuracy of the proposed method was confirmed using Certified Reference Materials, NMIJ CRM 7303-a (lacustrine sediment) from National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Japan, and MESS-3 (marine sediment) and PACS-2 (marine sediment) from National Research Council, Canada. The analytical results obtained by employing Pd/Mg modifier are in good agreement with the certified values of all the reference sediment materials. Although for NRC MESS-3 an accurate determination of zinc is achieved even without the chemical modifier, the use of Pd/Mg chemical modifier is recommended as it leads to establishment of a reliable and accurate direct analytical method. One quantitative analysis takes less than 15 minutes after we obtain dried sediment samples, which is several tens of times faster than conventional analytical methods using acid digested sample solutions. The detection limits are 0.13?µg?g?1 (213.9?nm) and 16?µg?g?1 (307.6?nm), respectively, in sediment samples, when 40?mg of dried powdered samples are suspended in 20?mL of 0.1?mol?L?1 nitric acid and a 10?µl portion of the slurry sample is measured. The precision of the proposed method is 8–15% (RSD). 相似文献
76.
Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO4·6H2O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO4·6H2O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm−1 with a small shoulder at around 2170 cm−1, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm−1 result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm−1 can be safely attributed to a stretching Mg–Ow mode. In the ν3(PO4) and ν4(PO4) region in the infrared spectra, one band in each is observed, at 995 and 559 cm−1, respectively. In the region of the ν1 modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm−1 which is only insignificantly shifted to 929 cm−1 in the spectrum of the perdeuterated compound. The band at 379 cm−1 in the Raman spectrum could be assigned to the ν2(PO4) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO4·6H2O and their deuterated compounds shows that ν1(PO4) and ν3(PO4) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites. 相似文献
77.
78.
Julia Intemann Dr. Jan Spielmann Dr. Peter Sirsch Prof. Dr. Sjoerd Harder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8478-8489
A new tetranuclear magnesium hydride cluster, [{ NN ‐(MgH)2}2], which was based on a N? N‐coupled bis‐β‐diketiminate ligand ( NN 2?), was obtained from the reaction of [{ NN ‐(MgnBu)2}2] with PhSiH3. Its crystal structure reveals an almost‐tetrahedral arrangement of Mg atoms and two different sets of hydride ions, which give rise to a coupling in the NMR spectrum (J=8.5 Hz). To shed light on the relationship between the cluster size and H2 release, the thermal decomposition of [{ NN ‐(MgH)2}2] and two closely related systems that were based on similar ligands, that is, an octanuclear magnesium hydride cluster and a dimeric magnesium hydride species, have been investigated in detail. A lowering of the H2‐desorption temperature with decreasing cluster size is observed, in line with previously reported theoretical predictions on (MgH2)n model systems. Deuterium‐labeling studies further demonstrate that the released H2 solely originates from the oxidative coupling of two hydride ligands and not from other hydrogen sources, such as the β‐diketiminate ligands. Analysis of the DFT‐computed electron density in [{ NN ‐(MgH)2}2] reveals a counterintuitive interaction between two formally closed‐shell H? ligands that are separated by 3.106 Å. This weak interaction could play an important role in H2 desorption. Although the molecular product after H2 release could not be characterized experimentally, DFT calculations on the proposed decomposition product, that is, the low‐valence tetranuclear Mg(I) cluster [( NN ‐Mg2)2], predict a structure with two almost‐parallel, localized Mg? Mg bonds. As in a previously reported β‐diketiminate MgI dimer, the Mg? Mg bond is not characterized by a bond critical point, but instead displays a local maximum of electron density midway between the atoms, that is, a non‐nuclear attractor (NNA). Interestingly, both of the NNAs in [( NN ‐Mg2)2] are connected through a bond path that suggests that there is bonding between all four MgI atoms. 相似文献
79.
Neil R. Judge Dr. Leonie J. Bole Prof. Eva Hevia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(10):e202104164
Advancing the understanding of using alkali-metal alkoxides as additives to organomagnesium reagents in Mg−Br exchange reactions, a homologous series of mixed-ligand alkyl/alkoxide alkali-metal magnesiates [MMg(CH2SiMe3)2(dmem)]2 [dmem=2-{[2-(dimethylamino)ethyl]methylamino} ethoxide; M=Li, 1 ; Na, 2 ; (THF)K, 3 ] has been prepared. Structural and spectroscopic studies have established the constitutions of these heteroleptic/heterometallic species, which are retained in arene solution. Evaluation of their reactivity towards 2-bromoanisole has uncovered a marked alkali-metal effect with potassium magnesiate 3 being the most efficient of the three ate reagents. Studies probing the constitution of the exchange product from this reaction suggest that the putative [KMgAr2(dmem)]2 (Ar=o-OMe−C6H4) intermediate undergoes redistribution into its single metal components [KAr]n and [MgAr(dmem)]2 ( 5 ). This process can be circumvented by using a different potassium alkoxide containing an aliphatic chain such as KOR’ (R’=2-ethylhexyl) which undergoes co-complexation with Mg(CH2SiMe3) to give [KMg(CH2SiMe3)2(OR’)]2 ( 7 ). This ate, in turn, reacts quantitatively with 2-bromoanisole furnishing [KMgAr2(OR’)]2 ( 9 ) which is stable in solution as a bimetallic compound. Collectively this work highlights the complexity of these alkali-metal mediated Mg−Br exchange reactions, where each reaction component can have a profound effect not only on the success of the reaction; but also the stability of the final metalated intermediates prior to their electrophilic interception. 相似文献
80.