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191.
本文采用电导、pH滴定法研究了乙醇-水溶液中希土与1′-苯基-3′-甲基-5′-氧代吡唑-4′-基乙醛酸(简称H2A)的配位反应.合成了15种新的希土固态配合物.通过元素分析、化学分析、水份分析确定了配合物的化学组成为RE(HA)3·nH2O(RE=Ce、Pr、Sm、Tm、Lu、n=1;RE=La、Nd、Eu、Gd、Tb、Dy、Ho、Er、Yb、Y,n=1-2).并对配合物的红外光谱、核磁共振谱、热稳定性、紫外光谱、溶解性及摩尔电导进行了测定. 相似文献
192.
Summary The novel theoretical scheme IMOMM, integrating ab initio and molecular mechanics contributions in a single geometry optimization process, is applied to the structural determination of different [OsO4(NR3)] (NR3 = bulky chiral alkaloid derivative) species closely related to active catalysts for the asymmetric dihydroxylation of olefins. Computed values compare in a satisfactory way with available X-ray data, the relationship between the Os-N distance and the nature of the NR3, ligand being properly reproduced. The computational scheme allows the separate quantification of electronic and steric effects, as well as the identification of the specific steric repulsions responsible for the difference. 相似文献
193.
194.
V. V. Dovlatyan K. A. Eliazyan V. A. Pivazyan A. P. Engoyan 《Chemistry of Heterocyclic Compounds》2003,39(9):1238-1241
We have carried out solvolysis of the previously described ethyl esters of 3-methyl(aryl)-4-methyl-2-thioxothiazoline-5-carboxylic acids, leading to the corresponding acids without breaking down the heterocycle. We synthesized a series of novel esters from the latter by treatment with dimethyl sulfate or reactive halides. Of these, only in the case of the ethyl ester of 3,4-dimethyl-2-thioxothiazoline-5-carboxylic acid did we obtain the hydrazinolysis product (the hydrazide), from which we synthesized novel hydrazones by treatment with aldehydes and ketones. 相似文献
195.
A. V. Belyakov A. V. Golubinskii L. V. Vilkov V. I. Shiryaev E. M. Styopina E. A. Kovalyova V. S. Nikitin 《Russian Chemical Bulletin》1993,42(2):346-349
The molecular structure of gaseous Br2Sn(CH2SiMe2)2O was studied by electron diffraction. The six-membered ring has a chair conformation whereas the entire molecule possessesC
s
symmetry. The existence of a boat conformer cannot be completely excluded. The results of theoretical calculations for a twisted-boat conformation are at variance with the experimental data. Steric strain caused by mutual repulsion of the two axial methyl groups is reduced to the tilt of the Me2Si fragments in opposite directions. This results in an increase (up to 26°C) in the angle formed by the bisector of the CM-Si-CM angle with the CcSiO plane. The main geometrical parameters are as follows:r
g (Å): Si-O 1.708(20); Si-CM 1.862(20); Si-Cc 1.882(9); Sn-C 2.108(26); Sn-Br 2.456(3); C-H 1.099(30); (degr.): C-Sn-C 105(2); Br-Sn-Br 107.9(1.2); Si-O-Si 129.6(3); CM-Si-CM 112; Si-C-H 113 (fixed value in accordance with experiment); Cc-Si-O 107(2); Sn-C-Si 109(2); torsion angles: (Si-C) 52(2); (Si-O) 62(1); (Cc-Sn) 54(1). The average amplitudes were fixed at the values calculated from the force field. Structural parameters of molecules with similar structures were analyzed and compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 384–387, February, 1993. 相似文献
196.
Vijay Singh 《Tetrahedron letters》2006,47(39):7043-7045
Tributyltin hydride-mediated straightforward synthesis of a new isoxazolo-benzazulene system from the derivatives afforded by the Baylis-Hillman reaction of 3-(2-bromophenyl)-4-isoxazolecarbaldehydes is described. 相似文献
197.
Kh. S. Shikhaliev A. V. Falaleev G. I. Ermolova A. S. Solov'ev 《Chemistry of Heterocyclic Compounds》2002,38(2):210-212
4,6,6-Trimethyl-1,4-dihydropyrimidines have been synthesized by condensation of 2-quinazolylguanidines with mesityl oxide. The analogous reaction with benzalacetone leads to unstable 4-methyl-6-phenyl-1,4-dihydropyrimidines, which are oxidized to the corresponding 4-methyl-6-phenylpyrimidines. 相似文献
198.
N. N. Kolos T. V. Berezkina V. D. Orlov Yu. N. Surov I. V. Ivanova 《Chemistry of Heterocyclic Compounds》2002,38(12):1491-1496
3-Benzoyl-2,3-dibromopropionic acid reacts with 4-substituted o-phenylenediamines to give 3-aryl-2-carboxymethylene-1,2-dihydroquinoxalines. 相似文献
199.
Uncoupled metabolism stimulated by chemical uncoupler and oxic-settling-anaerobic combined process to reduce excess sludge production 总被引:1,自引:0,他引:1
The effects of three uncoupled metabolic systems (conventional activated sludge process with the addition of 3,3′,4′,5-tetrachlorosalicylanilide
[TCS], oxic-settling-anaerobic [OSA] process modified by insertion of a sludge-holding tank in the sludge return line, and
TCS and OSA combined process) on reducing excess sludge production were studied. Compared with the control conventional activated
sludge process, the most effective system was the combined process, which could reduce excess sludge production by 46.90%.
The 180-d operation results confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield but that it
had an adverse effect on substrate removal capability, effluent nitrogen concentration, and sludge settleability. The OSA
process decreased excess sludge production by only 26% but had less adverse effect on effluent quality and could improve sludge
settleability. The effluent total phosphorous concentration of the three systems was slightly lower than of the control unit.
Microbial populations were monitored by both microscopic and molecular biologic analysis method (polymerase chain reaction
[PCR]-denaturing gradient gel electrophoresis [DGGE]). The presence of TCS caused metazoans to disappear and decreased the
number and activity of protozoa. PCR amplification of 16S rRNA and sequent DGGE analysis found a shift in the diversity of
the predominant species. The results imply that OSA combined with the chemical uncoupler process may effectively reduce excess
sludge yield and not affect process performance significantly. 相似文献
200.
Ye Qing Li Ming Lu Chun Xu Lu Sai Jian Zhu Qi Fa Liu 《中国化学快报》2007,18(11):1313-1315
A novel and simple procedure for synthesis of azanucleoside by Mitsunobu reaction between N-(p-nitrobenzyloxycarbonyl)- trans-4-hydroxy-D-proline methyl ester obtained from trans-4-hydroxy-L-proline after six-step reaction and 2-fluoro-6-azidopurine is described,and azanucleoside is fluorinated by new fluridizer 2,2-difluoro-1,3-dimethylimidazolidine (DFI).All reactions could be carded out under mild condition. 相似文献