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91.
The formation constants of the species formed in the systems H+ + thallium(I) + AMP and H+ + AMP have been determined in aqueous solutions of methanol at 25 degrees C and constant ionic strength 0.1 mol dm(-3) sodium perchlorate, using spectrophotometric and potentiometric techniques. Thallium(I) forms two mononuclear 1:1 complexes with AMP of the type TlHL and TlL- in the pH range of study (1-11), where L2- represents the fully dissociated ligand. The formation constants in various media were analyzed in terms of Kamlet and Taft's parameters. Single-parameter correlation of the formation constants, beta111, and beta101, versus alpha (hydrogen-bond donor acidity), beta (hydrogen-bond accepter basicity), and for pi* (dipolarity/polarizability) are relatively poor in all solutions, but multi-parameter correlation represents significant improvement with regard to the single-parameter models. Finally, the results are discussed in terms of the effect of the solvent on complexation. 相似文献
92.
Tahereh Ahmadi Ghodsi Mohammadi Ziarani Parisa Gholamzadeh Hoda Mollabagher 《Tetrahedron: Asymmetry》2017,28(5):708-724
Asymmetric multicomponent reactions (AMCRs) include the reaction of three or more reactants simultaneously to produce chiral products that they have some advantages containing simple procedures, saving time and energy, and being environmentally friendly processes. AMCRs have seen much development and their potent synthetic approaches are discussed in this review. 相似文献
93.
The synthesis of a novel class of aryl bis(dimethylamino)methylenecarbamodithioates via a copper-catalyzed S-arylation reaction of 1,1,3,3-tetramethylguanidine–heterocumulene adducts is described. 相似文献
94.
Ganjali MR Norouzi P Gol-Mohammadi M Mizani F Poursaberi T Salavati-Niasari M Shamsipur M Hosseini M Javanbakht M 《Annali di chimica》2003,93(7-8):679-690
A strontium Schiff's base complex (SS) can be used as a suitable ionophore to prepare a sulfate-selective PVC-based membrane electrode. The use of oleic acid (OA) and hexadecyltrimethylammonium bromide (HTAB), as additives, and nitrobenzen (NB), dibutyl phthalate (DBP) and benzyl acetate (BA) as solvent mediators, were investigated. The best performance was observed with a membrane composition PVC: NB: SS: HTAB of 30%: 62%: 5%: 3% ratio. The resulting sensor works well over a wide concentration range (1.0 x 10(-2)-1.0 x 10(-6) M) with a Nernstian slope of -29.2 mV per decade of sulfate activity over a pH range 4.0-7.0. The limit of detection of the electrode is 5 x 10(-7) M. The proposed sensor shows excellent discriminating ability toward SO4(2-) ions with regard to many anions. It has a fast response time of about 15 s. The membrane electrode was used to the determination of zinc in zinc sulfate tablets. The sensor was also used as an indicator electrode in the potentiometric titration of SO4(2-) against barium ion. 相似文献
95.
Tahereh Asadi Jae-chun Lee Mohammad Jahani 《Journal of Dispersion Science and Technology》2018,39(9):1328-1334
Solvent extraction of zinc from sulphate leach solution obtained from the treatment of a sulphide-oxide sample, was investigated using D2EHPA and Cyanex 272 diluted in kerosene in a batch reactor. According to the results, D2EHPA exhibited the higher extraction efficiencies than Cyanex 272 at the organic/aqueous ratio of 1:1. The optimum concentration and pH for D2EHPA and Cyanex 272 were distinguished to be 0.5?mol/L and 2.5, and 0.035?mol/L and 3.5, respectively. Under these conditions, extraction efficiency was found to be ~75% for D2EHPA against 41% for Cyanex 272. The plot of log D versus log [D2EHPA] confirmed the presence of 1 mole D2EHPA in dimeric form for 1 mole Zn in the extraction system. Thermodynamic data showed that the zinc extraction process is endothermic. For D2EHPA, two-stage simulated counter-current extraction experiments were performed on the basis of the McCabe-Thiele diagram and the extraction percentage of zinc was found to be about 88%. The synergistic effect of Cyanex 272 and TBP with D2EHPA was particularly investigated. It was found that the mixture of 80% D2EHPA and 20% Cyanex 272 exhibited the best synergistic effect for Zn-extraction with a synergistic coefficient of 1.04. 相似文献
96.
Hadi?RavanEmail authorView authors OrcID profile Tahereh?Fozooni Mojdeh?Amandadi Hosseinali?Sasan Akram?Norouzi 《Mikrochimica acta》2018,185(9):443
A DNAzyme-embedded hyperbranched DNA dendrimer is used as a colorimetric signal amplifier in an ultrasensitive detection scheme for nucleic acids. The hyperbranched DNA dendrimers were constructed by single-step autonomous self-assembly of three structure-free DNA monomers. A cascade of self-assembly reactions between the first and second strands leads to the formation of linear DNA concatemers containing overhang flank fragments. The third strand, which bears a peroxidase-mimicking DNAzyme domain, serves as a bridge to trigger self-assembly between the first and second strands across the side chain direction. This results in a chain branching growth of the DNAzyme-embedded DNA dendrimer. This signal amplifier was incorporated into the streptavidin-biotin detection system which comprises an adaptor oligonucleotide and a biotinylated capture probe. The resulting platform is capable of detecting a nucleic acid target with an LOD as low as 0.8 fM. Such sensitivity is comparable if not superior to most of the reported enzyme-free (and even enzyme-assisted) signal amplification strategies. The DNA dendrimer based method is expected to provide a universal platform for extraordinary signal enhancement in detecting other nucleic acid biomarkers by altering the respective sequences of adaptor and capture probe. 相似文献
97.
In this work, the Nin (n = 2–10) nanoclusters were investigated to design new catalysts for the selective hydrogenation of acetylene. Our results show that among the Nin nanoclusters, the Ni6 nanocluster can be used as a catalyst in the reactions of hydrogenation. In the presence of the Ni6 nanocluster, the Ea of the forward step in the reaction of conversion of vinyl to ethylene was 21.21 kJ/mol lower than that of the reverse step in the reaction of conversion of acetylene to vinyl. Also, the Ea of the forward step in the reaction of conversion of ethyl to ethane was 96.59 kJ/mol higher than that of the reverse step in the reaction of conversion of ethylene to ethyl. According to the obtained results, the Ni6 nanocluster can selectively act in the hydrogenation of a mixture of acetylene and ethylene. 相似文献
98.
Mohammad Ali Zolfigol Gholamabbas Chehardoli Ezat Ghaemi Elaheh Madrakian Reza Zare Tahereh Azadbakht Khodabakhsh Niknam Shadpour Mallakpour 《Monatshefte für Chemie / Chemical Monthly》2008,121(4):261-265
Various N-bromo reagents [HMTAB, DABCO-bromine, DPTBE, and TBCA] were used as effective oxidizing agents for the oxidation of urazoles and bisurazoles to their corresponding triazolinediones
under mild and heterogeneous conditions at room temperature with good to excellent yields. Also the oxidation of some new
4-phenylurazole derivatives with these reagents is discussed. 相似文献
99.
The present work describes the possibility of using pervaporation process to recover the pomegranate aroma compounds from an actual pomegranate juice and a model aroma solution. Four different chemicals representing four major kinds of aroma compounds, namely, 3-methyl butanal, isopentyl acetate, n-hexanol and α-ionone, were utilized in this work. Three POMS membranes and two PDMS membranes were tested for pervaporation and compared for their separation performance. The influence of various operating parameters such as feed flow rate, feed temperature and permeate pressure on the permeation flux and aroma compounds enrichment factor was investigated. Feed flow rate was shown to have no significant effect on both total flux and aroma enrichment factor, whereas feed temperature and permeate pressure had highly significant effects. An increase in feed temperature led to higher flux and enrichment factor. As permeate pressure increased, the flux and enrichment factor of some aroma compounds decreased. Some of the aroma compounds showed higher enrichment factor at higher permeate pressures. Finally, the activation energy of permeation and the membrane permeability for each aroma compound were determined. 相似文献
100.
An experimental and theoretical analysis to separate CO2 using facilitated transport membranes immobilized with different aqueous single and mixed amine solutions have been performed. The membranes containing monoethanolamine (MEA), diethanolamine (DEA), monoprotonated ethylenediamine (EDAH+) and piperazine (PZ), as well as aqueous blends of PZ with MEA, DEA or EDAH+ were considered. The aqueous solution of PZ showed the highest CO2 permeation rate with respect to other single amine solutions. Therefore blends of PZ with MEA, DEA and EDAH+ increased the permeance of carbon dioxide through mixed amine membranes. 相似文献