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41.
Nija A. Ellis Colin D. Hubbard Shailaja M. Shirodkar Pilar Guardado Maria-Luisa Moya Francisco Sanchez-Burgos John Burgess 《Transition Metal Chemistry》1989,14(6):466-470
Summary The kinetics of formation of the NiII and CoII complexes of pyridine 2-azo-p-dimethylaniline have been studied in aqueous ethylene glycol, aqueous glycerol and in moderate (up to 2.5 mol dm–3) concentrations of NaCl at 298.2K.Mole fractions of 0.24 and 0.12 respectively for ethylene glycol and glycerol effect a lowering of the formation rate constant Kf of Ni(PADA)2+ to about 50% of the value in water. A concentration of 2.0 mol dm–3 NaCl doubles kf for both the Ni and Co complexes. These findings are discussed within the framework of the dissociative interchange mechanism; the possible effects upon each step of the mechanistic pathway are considered. 相似文献
42.
Preparation of new unsymmetrical optically active (s)-(+)-naproxen dendrimers containing 2-hydroxymethyl-1,4-butanediol and 2,2-bis(hydroxymethyl)-1,4-butanediol cores is described. These polyarylester dendrimers are unsymmetrical with respect to chain lengths and aid in studying controlled drug delivery based on differential enzymatic cleavage. Synthesis of a new acid dendritic wedge containing (s)-(+)-naproxen is also reported. 相似文献
43.
Nongeminally substituted cyclic phosphazenes with various haloalkyl substituents were prepared using deprotonation-substitution reactions at the methyl groups of the cis isomers of nongeminally substituted cis-[Me(Ph)P=N]3, 2. Treatment of 2 with n-BuLi followed by reaction with organic halogenated reagents (RX=C2Cl6, BrC(O)CMe2Br, and ICH2COOEt) at low temperature afforded the various cyclic derivatives cis-[(XCH2)(Ph)PN]3 (3, X=Cl, 4, Br, and 5, I). The mono- and dibromoalkyl derivatives, cis-[Ph3(BrCH2)Me2P3N3], 6, and [Ph3(BrCH2)2MeP3N3], 7, were also isolated along with 4 when the electrophile was dibromoethane. Reaction of cis-[Ph(BrCH2)PN]3, 4, with KSC(O)Me gave cis-[Ph(MeC(O)SCH2)PN]3, 8. The structures of all the cis cyclic phosphazenes were determined by NMR spectroscopy and X-ray diffraction. All retained the basketlike shape with the hydrophobic phenyl groups opposite the haloalkyl groups on the P3N3 ring. Thermal analysis of the new cyclic trimers indicates that ring-opening polymerization does not occur. The melting points and the thermal stabilities of haloalkyl cyclophosphazenes were higher than those of the parent compound 2. 相似文献
44.
Abstract A series of unsymmetrical dimeric mesogens was prepared, members of which were composed of a 4′-pentyloxybiphenyl-4-carboxyl core and a 4′-substituted-benzylidene-4-oxyaniline core joined via an alklyene spacer. The structural variants were cyano, nitro and trifluoromethyl. Comparison of mesophase behaviour of the unsymmetrical dimers with that of corresponding monomeric ‘halves’ and also with that of corresponding symmetrical dimers indicated a tendency for the unsymmetrical dimers to form smectic phases although not as highly ordered as those of some of the monomers corresponding to a relevant core group. 相似文献
45.
Patty Wisian-Neilson June-Ho Jung Srinagesh K. Potluri Clayton E. Mauldin Hongming Zhang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4-5):817-820
A series of new nongeminally-substituted cyclic phosphazenes with various substituents has been prepared via deprotonation-substitution reactions at the Me groups of both the cis and trans isomers of [(Me)(Ph)PN] 3 . Treatment of [(Me)(Ph)PN] 3 with n-BuLi followed by reaction with organic electrophilic reagents affords a variety of cyclic derivatives, [(RCH 2 )(Ph)PN] 3 , [R = Me, Cl, Br, I, (CH 2 ) 2 Br, CH 2 CH═CH 2 , SR, C(═O)OLi, C(═O)OMe, C(═O)OEt]. The structures of theses cis cyclic phosphazenes, which were obtained by x-ray diffraction, illustrate the basket-like shape of the molecules. Heating the cis and trans isomers of the parent [(Me)(Ph)PN] 3 produced mixtures of cyclic trimers and tetramers. The latter were isolated and characterized by x-ray crystallography. Nanoparticles of gold and silver were prepared by reduction of metal salts with a reducing agent in the presence of selected trimers. 相似文献
46.
Cyclic hydroxamic acids 3 and 4 are the unexpected products in the reaction of 0-(2-aminobenzoyl) hydroxylamine 1 and orthoesters, acid chlorides, ethyl chloroformate. 相似文献
47.
A mild, rapid and highly regioselective opening of epoxides by mercaptans to β-hydroxy sulfides and benzoxathiepinones has been achieved in excellent yields, using catalytic amount of (bromodimethyl)sulfonium bromide in solvent free reaction conditions. 相似文献
48.
Determination of rare earth elements in Indian kimberlite using inductively coupled plasma mass spectrometer (ICP-MS) 总被引:1,自引:0,他引:1
Sanjukta A. Kumar Shailaja P. Pandey Sangita D. Kumar 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(3):419-424
A method has been developed for the analysis of rare earth elements (REEs) in kimberlite samples using inductively coupled plasma mass spectrometer (ICP-MS). The samples were dissolved using sodium peroxide fusion and after appropriate dilutions the solutions were analyzed using ICP-MS. The paper presents the concentration of rare-earth elements as determined by ICP-MS in eight kimberlite samples from Central India. The method was validated using certified reference materials STSD-1 and STSD-2 from Canadian Certified Reference Material Project. The method detection limit of various REEs varies from 0.12 to 1.54?mg?kg?1. The total REE concentrations range from 418 to 726?mg?kg?1 and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those for kimberlites. In order to compare ICP-MS results, the samples were analyzed using instrumental neutron activation analysis which is a reference method for determination of REEs in geological samples. 相似文献
49.
K. Venkatesh Sumit Chhillar Granthali S. Kamble Shailaja P. Pandey Manisha Venkatesh Sanjukta A. Kumar Sanjiv Kumar R. Acharya P. K. Pujari A. V. R. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(3):1425-1428
Boron is an important element in nuclear technology. A comparative study was carried out for the determination of boron in borosilicate glass, boron carbide and graphite samples by wet-chemical and nuclear analytical methods. Wet chemical methods namely titrimetry, Inductively Coupled Plasma Mass Spectrometry and ICP Optical Emission Spectrometry and nuclear analytical methods namely Particle Induced Gamma-Ray Emission and Nuclear Reaction Analysis were used. Boron concentrations were in trace (mg kg?1) level in graphite and percentage level in borosilicate glass and boron carbide. 相似文献
50.
A new clean protocol for protection of aryl and aliphatic amines with t-butoxycarbonyl (t-BOC) and benzyloxycarbonyl (Cbz) catalyzed by simple (bromodimethyl)sulfonium bromide has been developed. Rapid protection of amines in excellent yields in totally solvent-free conditions has been achieved. 相似文献