排序方式: 共有198条查询结果,搜索用时 343 毫秒
1.
2.
Abdolhassen Talebian Alem Ghiorghis Charles F. Hammer Evelyn A. Murril Frank Pallas 《Journal of heterocyclic chemistry》1992,29(4):979-984
The syntheses and spectroscopic properties (ir, 1H nmr, 13C nmr, uv and ms) of pure samples of 2-chloro-4,6-bis(dimethylamino)-s-triazine 1 , 4,6-dichloro-2-dimethylamino-s-triazine 2 , 4,6-bis(dimethylamino)-s-triazin-2(lH)-one 3 , 4-chloro-6-dimethylamino-s-triazin-2(1H)-one 4 , 6-dimethylamino-s-triazine-2,4(1H,3H)-dione 5 , and 2,4,6-tris(dimethylamino)-s-triazine (altretamine, HMM) are reported. Evidence for enol-keto equilibria are also presented for 3 , in which the enol form exhibits as an H-bonded dimer structure similar to the dimer of organic carboxylic acids. 相似文献
3.
Ramin Ghorbani‐Vaghei Mohammad Ali Zolfigol Nasrin Moshfeghifar Nadiya Koukabi Gholamabbas Chehardoli 《中国化学会会志》2007,54(3):791-794
An efficient method for the oxidative coupling of thiols to their corresponding disulfides by new reagents poly(N‐bromobenzene‐1,3‐disulfonylamide) PBBS , N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonylamide TBBDA and DABCO‐bromine complex is described. The reaction was applicable to a variety of thiols with high chemoselectivity. 相似文献
4.
The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO2), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and Vmodifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry. 相似文献
5.
Ricerche di Matematica - Let G be a finite group and $$N \unlhd G$$ . The normal subgroup based power graph of G, $$\Gamma _N(G)$$ , is an undirected graph with vertex set $$(G{\setminus }N) \cup... 相似文献
6.
Kinetics of the addition reaction of triphenylphosphine to para‐benzoquinone in 1,2‐dichloroethane as solvent was studied. Initial rate method was used to determine the order of the reaction with respect to the reactants. Pseudo‐first‐order method was also used to calculate the rate constant. This reaction was monitored by UV‐vis spectrophotometry at 520 nm by variable time method. On the basis of the obtained results, the Arrhenius equation of this reaction was obtained: The activation parameters, Ea, ΔH#, ΔG#, and ΔS# at 300 K were 5.701, 6.294, 19.958 kcal mol?1 and ?45.853 cal mol?1 K?1, respectively. This reaction is first and second order with respect to triphenylphosphine and para‐benzoquinone, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:472–479, 2004 相似文献
7.
Majid M. Heravi Nasrin Farhangi Yahya Sh. Beheshtiha Karim Assadolah Mitra Ghassemzadeh Koroush Tabar-Hydar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2883-2885
In an environmentally benign system, alcohols are rapidly oxidized to carbonyl compounds using CrO 3 supported onto wet silica gel as an oxidant under microwave irradiation. 相似文献
8.
Tungstate ions were successfully loaded onto triazine‐based ionic liquid‐functionalized magnetic nanoparticles through an anion exchange process. The use of triazine core for creating ionic liquid led to the immobilization of high amounts of WO42?. The resulting catalyst showed high activity and selectivity in the oxidation of sulfides to sulfoxides with H2O2 as a green oxidant at room temperature. In addition, due to the presence of ammonium groups in the catalyst structure, water dispersibility of the catalyst was increased. More important, the catalyst was magnetically recovered and reused for up to six runs without any marked decrease of activity and selectivity. Finally, easy gram‐scale oxidation of methylphenyl sulfide as well as fast separation of catalyst and product makes the protocol economical and industrially applicable. 相似文献
9.
A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi‐layered poly(2‐dimethylaminoethyl acrylamide)‐coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one‐pot three‐component reaction of alkyl halide, sodium azide and alkyne, known as copper‐catalyzed click synthesis of 1,2,3‐triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of alkyl/benzyl/allyl bromide/chloride and alkyl/aryl terminal alkynes without isolation of azide intermediate, and good to excellent yields of products make this procedure highly economical. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
We calculated the Verdet constant for first six groups of alcohols. Verdet constant is the rotation angle of a plane polarized light beam passing through a medium in a magnetic field, divided by the field strength and by the path length. Calculated ranges are in the wavelengths between 400 and 850 nm in gas and liquid phases. By plotting the obtained results, it can be seen that the Verdet constant decreases with increase in the wavelength, and this is commonly known for the mathematical relations. In our experiment we had intermolecular interactions which were negligible. For obtained results we observe some errors, but these errors are negligible and it will be lesser in high wavelengths. 相似文献