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21.
Equilibria and kinetics for the extraction of nickel(II) and copper(II) by 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N) in seven organic solvent systems were studied in order to test the validity of several hypotheses related to the role of the solvent in equilibrium and kinetic aspects of metal chelate extraction. For the nickel—LIX 65N system, the extraction constant is essentially independent of the solvent system, whereas for the copper—LIX 65N system, the extraction constant is not independent of solvent; this indicates that while the stoichiometry of the nickel chelate remains the same in all solvents, that of copper does not. The observed rate constant for the nickel—LIX 65N extraction was found to vary inversely with the LIX 65N distribution constant as predicted from a mechanism involving slow formation of the 1:1 complex. The observed reaction rate constant for the copper—LIX 65N varied inversely with the square of the distribution constant, also in accordance with the previously postulated mechanism of the slow formation of the 2:1 copper complex. This study, therefore, unequivocally eliminates the interfacial mechanism in favor of the homogeneous chemical reaction mechanism for the extraction of metal ions by LIX 65N, as well as by other similar high-molecular-weight extractants. 相似文献
22.
A membrane having an amine moiety was prepared by plasma-grafting 2-(N,N-dimethyl)aminoethyl methacrylate (DAMA) onto a microporous polyethylene substrate. Permselectivity of the membrane for CO2 over N2 was achieved in both dry and water swollen conditions. When the CO2 partial pressure in the feed gas was 0.047 atm, the selectivity of CO2 over N2 reached 130 for the highly swollen water containing membrane. This value was found to agree with that obtained with a mobile carrier membrane (supported liquid membrane) using DAMA as the carrier. The effects of several experimental conditions such as degree of grafting, feed partial pressure and temperature on the membrane performance were studied. It was suggested that the membrane acted as a fixed carrier membrane for CO2 facilitated transport in under the dry condition and acted as a fixed reaction site membrane in the water swollen condition. The carrier transport mechanism is discussed for dry and aqueous membranes. 相似文献
23.
Yamashita M Yamamoto Y Akiba KY Hashizume D Iwasaki F Takagi N Nagase S 《Journal of the American Chemical Society》2005,127(12):4354-4371
Pentacoordinate and tetracoordinate carbon and boron compounds (27, 38, 50-52, 56-61) bearing an anthracene skeleton with two oxygen or nitrogen atoms at the 1,8-positions were synthesized by the use of four newly synthesized tridentate ligand precursors. Several carbon and boron compounds were characterized by X-ray crystallographic analysis, showing that compounds 27, 56-59 bearing an oxygen-donating anthracene skeleton had a trigonal bipyramidal (TBP) pentacoordinate structure with relatively long apical distances (ca. 2.38-2.46 A). Despite the relatively long apical distances, DFT calculation of carbon species 27 and boron species 56 and experimental accurate X-ray electron density distribution analysis of 56 supported the existence of the apical hypervalent bond even though the nature of the hypervalent interaction between the central carbon (or boron) and the donating oxygen atom was relatively weak and ionic. On the other hand, X-ray analysis of compounds 50-52 bearing a nitrogen-donating anthracene skeleton showed unsymmetrical tetracoordinate carbon or boron atom with coordination by only one of the two nitrogen-donating groups. It is interesting to note that, with an oxygen-donating skeleton, the compound 61 having two chlorine atoms on the central boron atom showed a tetracoordinate structure, although the corresponding compound 60 with two fluorine atoms showed a pentacoordinate structure. The B-O distances (av 2.29 A) in 60 were relatively short in comparison with those (av 2.44 A) in 59 having two methoxy groups on the central boron atom, indicating that the B-O interaction became stronger due to the electron-withdrawing nature of the fluorine atoms. 相似文献
24.
Yamashita M Kamura K Yamamoto Y Akiba KY 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(13):2976-2979
A novel potential tridentate ligand, 1,8-bis(dimethylamino)-9-bromoanthracene, was synthesized. The key steps are as follows: 1) dimethylamination of 1,8-dibromo-9-methoxyanthracene by a modified Buchwald's method to afford 1,8-bis(dimethylamino)-9-methoxyanthracene, and 2) reduction of the methoxy group by LDBB (lithium di-tert-butylbiphenylide) followed by treatment with BrCF2CF2Br. The corresponding 1,8-bis(dimethylamino)-9-lithioanthracene, which should be a useful versatile tridentate ligand, could be generated by treatment of the bromide with one equivalent of nBuLi. The lithioanthracene reacted with B-chloroborane derivatives to give three 9-boryl derivatives. Although we recently reported that the crystal structure of 1,8-dimethoxy-9-B-catecholateborylanthracene was a symmetrical compound with the almost identical two O-B distances (2.379(2) and 2.441(2) A), the newly prepared 1,8-bis(dimethylamino)-9-borylanthracene derivatives clearly have unsymmetrical structures with coordination of only one NMe2 group toward the central boron atom. However, the energy difference between the unsymmetrical and symmeterical structures was found to be very small based on 1H NMR measurements, in which symmetrical anthracene patterns in the aromatic region (two kinds of doublets and a triplet) and a sharp singlet signal of the two NMe2 groups were observed even at -80 degrees C. 1,8-Bis(dimethylamino)-9-bromoanthracene itself can be a versatile ligand for transition metal compounds. In fact, direct palladation of the bromide took place by the reaction with [Pd2(dba)3].CHCl3 in THF to give the 9-palladated product. X-ray crystallographic analysis of the Pd compound showed that the square planar palladium atom was coordinated in a symmetrical fashion by both NMe2 groups (Pd-N bonds are 2.138(5) and 2.146(5) A). 相似文献
25.
Hajime Kabashima Hideto Tsuji Hideshi Hattori 《Reaction Kinetics and Catalysis Letters》1996,58(2):255-259
All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively. 相似文献
26.
Synthesis and Rearrangement of P‐Nitroxyl‐Substituted PIII and PV Phosphanes: A Combined Experimental and Theoretical Case Study
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Tobias Heurich Dr. Zheng‐Wang Qu Dr. Senada Nožinović Dr. Gregor Schnakenburg Dr. Hideto Matsuoka Prof. Dr. Stefan Grimme Prof. Dr. Olav Schiemann Prof. Dr. Rainer Streubel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10102-10110
Low‐temperature generation of P‐nitroxyl phosphane 2 (Ph2POTEMP), which was obtained by the reaction of Ph2PH ( 1 ) with two equivalents of TEMPO, is presented. Upon warming, phosphane 2 decomposed to give P‐nitroxyl phosphane P‐oxide 3 (Ph2P(O)OTEMP) as one of the final products. This facile synthetic protocol also enabled access to P‐sulfide and P‐borane derivatives 7 and 13 , respectively, by using Ph2P(S)H ( 6 ) or Ph2P(BH3)H ( 11 ) and TEMPO. Phosphane sulfide 7 revealed a rearrangement to phosphane oxide 8 (Ph2P(O)STEMP) in CDCl3 at ambient temperature, whereas in THF, thermal decomposition of sulfide 7 yielded salt 10 ([TEMP‐H2][Ph2P(S)O]). As well as EPR and detailed NMR kinetic studies, indepth theoretical studies provided an insight into the reaction pathways and spin‐density distributions of the reactive intermediates. 相似文献
27.
28.
Dr. Dinar Abdullin Dr. Hideto Matsuoka Dr. Maxim Yulikov Nico Fleck Dr. Christoph Klein Dr. Sebastian Spicher Dr. Gregor Hagelueken Prof. Dr. Stefan Grimme Prof. Dr. Arne Lützen Prof. Dr. Olav Schiemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(37):8820-8828
Pulsed EPR dipolar spectroscopy (PDS) offers several methods for measuring dipolar coupling and thus the distance between electron-spin centers. To date, PDS measurements to metal centers were limited to ions that adhere to the high-field approximation. Here, the PDS methodology is extended to cases where the high-field approximation breaks down on the example of the high-spin Fe3+/nitroxide spin-pair. First, the theory developed by Maryasov et al. (Appl. Magn. Reson. 2006 , 30, 683–702) was adapted to derive equations for the dipolar coupling constant, which revealed that the dipolar spectrum does not only depend on the length and orientation of the interspin distance vector with respect to the applied magnetic field but also on its orientation to the effective g-tensor of the Fe3+ ion. Then, it is shown on a model system and a heme protein that a PDS method called relaxation-induced dipolar modulation enhancement (RIDME) is well-suited to measuring such spectra and that the experimentally obtained dipolar spectra are in full agreement with the derived equations. Finally, a RIDME data analysis procedure was developed, which facilitates the determination of distance and angular distributions from the RIDME data. Thus, this study enables the application of PDS to for example, the highly relevant class of high-spin Fe3+ heme proteins. 相似文献
29.
To prepare cross‐linked silicone (silicone rubber) particles in an aqueous medium, we investigated two synthesis methods involving a miniemulsion system. The first method was based on cationic ring‐opening polymerization of cyclic siloxane, which is a common synthetic route for linear silicone oil and uses octamethylcyclotetrasiloxane (D4) as the monomer and dimeric D4 (bis‐D4) as the cross‐linker. Although this method produces silicone particles, the particles do not remain in the particulate state after drying because of low cross‐linking density. The polymerization mechanism of this method was also investigated, which proceeds under the ring‐opening reaction of D4 in monomer droplets and upon polycondensation of hydrolyzed D4, which occurs in the water phase (ie, outside the monomer droplets). This mechanism implied that introducing the cross‐linking structure into particles is difficult because of the low solubility of bis‐D4 in water. To overcome these difficulties, we demonstrated a second method of preparing silicone particles based on the thiol‐Michael addition reaction between thiol‐terminated silicone oil and triacrylate in miniemulsion systems. Transmission electron microscopy images indicated that the silicone particles obtained in the particulate state upon drying and the aggregates of these particles showed elasticity. 相似文献
30.