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41.
A commercial cation exchange resin Amberlite 200 has been modified after immersion in solutions of polyethyleneimine (PEI). The kinetic of fixation of the metallic ions have been determined. The modification of the surface of the resin deals with a change in the order of the affinities of the resins towards cations. The retention is the function of the formation and the stability of the complex. The conditions of modification (pH, PEI concentration and time of immersion) have been examined and the modification was confirmed by the determination of the exchange capacities, the distribution coefficient (P) and the selectivity factors (S). The obtained results revealed the effect of PEI on the exchange properties of the resin. The pH range selected (6-8) permitted a good adherence of PEI onto the resin surface. The quantity of the adsorbed PEI was increased by raising the initial concentration and the immersion period. The exchange capacity for copper ion passed from 2.6 mmol g−1, in the case of unmodified resin, to 3.9 mmol g−1 for the modified one. 相似文献
42.
Sulfinyl fluoride and N-(F-isoprophyl)iminosulfur difluoride form the compounds, O(CH3) and i-C3F7N(CH3 with symdimethylethylenediamine (1). In contrast, CF3C(O)NSF2 and (Rf)2SF2 (Rf = CF3, i-C3F7 form only acyclic compounds, CF3C(O)N(CH3)CH2CH2N(CH3)C(O)CF3 and RfSN(CH3)CH2CH2N(CH3)SRf with (1). With PF3, PF5 and OPF3, cyclic compounds F, F3, and -(O)F result. When the latter two compounds are reacted further with LiNC(CF3)2, N(CH3)CH2CH2N(CH3)PF2NC(CF3)2 and (O)NC(CF3)2) form. 相似文献
43.
Iványi T Vander Heyden Y Visky D Baten P De Beer J Lázár I Massart DL Roets E Hoogmartens J 《Journal of chromatography. A》2002,954(1-2):99-114
This paper focuses on the classification or differentiation of RP-HPLC columns based on measured chromatographic properties. A chemometric study has been conducted on a published data set consisting of 85 RP-HPLC columns and on a data set consisting of 47 self-tested columns. Principal component analysis enables determination of the number of parameters necessary for a rational differentiation. The results show that reducing the number of parameters for such differentiation still allows classification of the columns just as a higher number did. It is shown that three test parameters produce a classification similar to that obtained with five parameters. 相似文献
44.
In the context of a European project, a new approach of sampling of volatile polycyclic aromatic hydrocarbons (PAHs) from air was developed. In fact, the aim of this project was to test the efficiency of an air cleansing prototype reactor, which was operating by non-thermal plasmolysis. With an eye to model the atmosphere ejected by the prototype, we needed to vaporise the volatile PAHs in an air stream at concentrations as low as those recommended by European Directives (96/62/CE) for PAHs in ambient air (i.e. 1 ng m−3). Our strategy was based on the analysis of PAHs trapped in an aqueous medium, in order to avoid important losses of volatile compounds observed during the delicate desorption-concentration step when classical solid supports are used. Then a study was carried out to determine: the design of the collecting part, the flow-rate of the air sampling, the nature and concentration of chemical additives used to enhance PAH solubility in water. The very highly diluted aqueous media obtained after the bubbling step were concentrated by solid-phase extraction (SPE) on hydrophobic cartridges and analysed on-line by reversed-phase HPLC with UV and fluorimetric detections. Lastly, the sampling technique was directly applied to the outlet of the air cleansing prototype and the analysis after 3-6 h of non-thermal plasmolysis showed that the target volatile PAHs were not present in an air stream initially polluted by volatile organic compounds. 相似文献
45.
N. Bélaïd-Drira H. Zamali M. Jemal 《Journal of Thermal Analysis and Calorimetry》1996,46(5):1449-1458
Phase diagram of the binary system LiNO3-NaNO3 has been obtained by using direct and differential thermal analysis between 323 and 623 K. This system is characterized by an eutectic plateau at 467 K. The eutectic point is at 0.465 mole NaNO3. A peritectic appears at 550 K. There is no miscibility in the solid state. These findings associated with some other thermodynamic results have been used to calculate the activities of the constituents along the liquids curve and the excess thermodynamic functions at 618 K. The constituents seem not to have a symmetrical influence on the thermodynamic quantities. 相似文献
46.
Vincent Lapinte Laurent Fontaine Vronique Montembault Irne Campistron Danile Reyx 《Journal of molecular catalysis. A, Chemical》2002,190(1-2):117-129
ROMP and retro-acyclic diene metathesis (ADMET) were used for the synthesis of new functional polymers and functional oligomers, respectively. Purely exo and enantiomerically pure norbornene and 7-oxanorbornene derivatives were prepared using stereospecific synthesis, effective fractionation and high yield condensation reactions. Successful ROMPs of those monomers were performed using either the new carbenic Schrock’s or Grubb’s catalysts or in some cases a classical bicomponent catalyst. New functional polymers such as optically active poly(norbornene-2-carboxylic acid), reactive poly(norbornene-2-azlactone), and side-chain liquid crystal polyoxanorbornenes were fully characterized. On the other hand, successful depolymerizations of 1,4-polyisoprene and of epoxidized 1,4-polybutadiene via cross-metathesis with 4-octene were performed using a stabilized bicomponent catalyst and the Grubb’s catalyst, respectively. Conditions for the controlled synthesis of epoxidized oligobutadienes and of epoxydienic monomers via retro-ADMET were clearly defined. 相似文献
47.
Abstract —5-Bromouridine (BrUd) photochemically reacted with l -tryptophan (trp) only in aqueous frozen solution giving rise to 2-[1,2,3,4-tetrahydro-1-(β-d -ribofuranosyl)-2,4-dioxo-5-pyrimidinyl]-l -tryptophan ( 1a ). Under similar conditions irradiation of 5-bromouracil (BrU) and trp gave the corresponding coupled product 2. Addition of acetone, potassium carbonate or sodium chloride to the frozen system completely inhibited the photocoupling reaction. These photocoupling reactions are suggested to proceed via mixed aggregate formation between trp and BrUd (or BrU) in frozen aqueous solution. Stacking interactions in these aggregates are characterized by an efficient quenching of trp fluorescence by BrUd. Under the same conditions other amino acids such as phenylalanine, tyrosine, histidine and lysine did not react with BrUd, indicating that the photocoupling of BrUd (or BrU) is specific for trp. 相似文献
48.
Sandrine PerocheHélène Parrot-Lopez 《Tetrahedron letters》2003,44(2):241-245
A new series of fluorinated amphiphilic β-cyclodextrin derivatives has been synthesized. The strategy is based on the modification of the C-6 position of the mono-6-deoxy-6A-para-tolylsulfonyl, di-6A, 6D-deoxy-6A, 6D-(para-tolylsulfonyl) and heptakis-(6-deoxy-6-iodo)-β-cyclodextrin precursors. The synthesis lead to mono-perfluoroalkylthio-, di-perfluoroalkylthio- and heptakis-perfluoroalkylthio-β-cyclodextrin in excellent yields (90-99%). 相似文献
49.
A number of α-β acetylenic carbinols RFCCC(OH)RR′, in which the acetylenic proton was substituted by a F-alkyl group, were first prepared, from a classical reaction of (F-alkynyl)- lithium derivatives RFCCLi upon various carbonyl compounds.On another hand, the reaction of propargyl bromide metallic complexes (organoaluminic, or ultrasonic irradiation activated organozinc) upon some polyfluorinated ketones RFCOR led to the formation, in convenient yields, of the propargylic carbinols HCCCH2C(OH)RRF.The synthesis and properties of these series of new (F-alkyl) substituted acetylenic and propargylic alcohols are described and discussed. 相似文献
50.
Hétérocycles à fonction quinone. 7. Benzo[f]quinazolinediones-7,10 à action antitumorale potentielle
Hlne Parrot-Lopez Jean-Michel Delacotte Jean Renault Suzanne Cros 《Journal of heterocyclic chemistry》1986,23(4):1039-1043
Few benzo[f]quinazoline-7,10-diones 4a-c are prepared by oxidation, with potassium nitrosodisulfonate, of the corresponding benzo[f]quinazolinamines, made by reduction of the nitro analogues which were obtained from 8-methoxybenzo[f]quinazolin-1(2H)-one. The compound 4a shows an interesting cytotoxicity. 相似文献