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131.
Lawrence JR Glass SV Park SC Nathanson GM 《The journal of physical chemistry. A》2005,109(33):7458-7465
The entry of HCl into 60-68 wt % D(2)SO(4) and HBr into 68 wt % acid containing 0-0.18 M 1-butanol was monitored by measuring the fractions of impinging HCl and HBr molecules that desorb as DCl and DBr after undergoing H --> D exchange within the deuterated acid. The addition of 0.18 M butanol to the acid creates butyl films that reach approximately 80% surface coverage at 213 K. Surprisingly, this butyl film does not impede exchange but instead enhances it: the HCl --> DCl exchange fractions increase from 0.52 to 0.74 for 60 wt % D(2)SO(4) and from 0.14 to 0.27 for 68 wt % D(2)SO(4). HBr --> DBr exchange increases even more sharply, rising from 0.22 to 0.65 for 68 wt % D(2)SO(4). We demonstrate that this enhanced exchange corresponds to enhanced uptake into the butyl-coated acid for HBr and infer this equivalence for HCl. In contrast, the entry probability of the basic molecule CF(3)CH(2)OH exceeds 0.85 at all acid concentrations and is only slightly diminished by the butyl film. The OD groups of surface butanol molecules may assist entry by providing extra interfacial protonation sites for HCl and HBr dissociation. The experiments suggest that short-chain surfactants in sulfuric acid aerosols do not hinder heterogeneous reactions of HCl or HBr with other solute species. 相似文献
132.
Michael Ptzel Andreas Schulz Jürgen Liebscher Wolfgang Richter Monika Richter 《Journal of heterocyclic chemistry》1992,29(5):1209-1211
Cyclic N-cyanocarbonimidodithioesters 4 or N-aroylcarbonimidothioic acid esters 10 react regioselectively with arylhydrazines and methylhydrazine by a ring chain transformation reaction forming ω-functionalized 3-alkylthio-1,2,4-triazoles 8 and 11 or 5-alkylthio-1,2,4-triazoles 9 . 相似文献
133.
Structures of Bis(trifluoromethyl)halogeno and thiocyanato Mercurates, [Hg(CF3)2X]— (X = Br, I, SCN), and a Comparison of the Structural Parameters of the CF3 Groups [(18‐C‐6)K]2[Hg(CF3)2SCN]2 (1) and [P(CH3)(C6H5)3]2[Hg(CF3)2X]2 (X = Br (2) , I (3) ) are prepared and their crystal structures are determined. [(18‐C‐6)K]2[Hg(CF3)2SCN]2 (1) crystallizes in the monoclinic space group P21/c with Z = 2, [P(CH3)(C6H5)3]2[Hg(CF3)2Br]2 (2) in the monoclinic space group P21/n with Z = 2 and [P(CH3)(C6H5)3]2[Hg(CF3)2I]2 (3) in the triclinic space group P1¯ with Z = 1. In the solid state the three compounds form dimeric anions with planar Hg2X2 rings. The structural parameters of the Hg(CF3)2 units in the till now known bis(trifluoromethyl)halogeno mercurates are compared. In all compounds one nearly symmetric and one distorted CF3 group exist. The largest differences of the C—F bond lengths is found for [(18‐C‐6)K][Hg(CF3)2I]. This can be regarded as the experimental evidence for the properties of trifluoromethyl mercury compounds to act as excellent difluorocarbene sources in the presence of alkali iodides. 相似文献
134.
A model iodophenyl imidazole ribonucleoside has been synthesized to study biodistribution properties in laboratory animals. The key intermediate 5-amino-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazole-4-[N-(p-iodophenyl)carboxamide] ( 5 ) was synthesized by coupling N-succinimidyl-5-amino-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazole-4-carboxylate ( 4 ) and p-iodoaniline. Deacetylation of the intermediate compound gave 5-amino-1-β-D-ribofuranosylimidazole-4-[N-(p-iodophenyl)]carboxamide ( 6 ). Ring annulation via diazotization of 5 gave 7-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazo[4,5-d]-v-triazin-[3-N-(p-iodophenyl)]-4-one ( 7 ). Subsequent deacetylation of 7 afforded 7-β-D-ribofuranosylimidazo[4,5-d]-v-triazin-[3-N-(p-iodophenyl)]-4-one ( 8 ). The radiolabeled compounds, [125I] 5 and [125I] 6 were prepared in a manner similar to the corresponding unlabeled compounds except that p-[125I]iodoaniline was used for coupling with 4 . Biodistribution studies of iodine-125-labeled 5 and 6 were performed in female Fischer rats and tumor bearing nude mice. Compound 6 showed uptake in the brain and proliferating tissues such as tumor and bone-marrow. 相似文献
135.
[graph: see text] High-level ab initio calculations indicate that *CH3 addition to the sulfur center of S=P(Z)(Z')SCH3 (Z,Z' = CH3, CN, OCH3, Ph) is considerably less exothermic than addition to the corresponding RAFT agents, S=C(Z)SCH3. This suggests that dithiophosphinate esters may have only limited use in controlling free-radical polymerization, but should make excellent radical chain carriers in organic synthesis. The results cast doubt on the notion that phosphoranyl radicals are more "intrinsically" stabilized than carbon-centered radicals. 相似文献
136.
Six known metabolites, two new isocoumarins 4 and 8, and one new highly substituted benzoic acid derivative 9 were isolated from the ethyl acetate culture extract of a fungal endophyte, Scytalidium sp. In addition, another new benzoic acid 10 with an unusual 1,2-dicarbonyl side chain was indirectly identified from its methylated derivatives 10a-10d. 相似文献
137.
In the presence of calcium, DNA and unilamellar liposomes of the zwitterionic lipid DPPC form a complex in which DNA strands are embedded between a lamellar phase of DPPC. In some complexes, in-plane alignment of the DNA strands occurs, where a DNA-DNA interaxial distance can be measured using small-angle X-ray scattering. Here we report a higher level of DNA organization, with a rectangular columnar phase of DNA identified within this complex structure. This observation is important in view of recent interests in creating new synthetic systems at the interface of biology. 相似文献
138.
Asymmetric hydrogenation of ketone 1 using trans-RuCl(2)[(R)-xylbinap][(R)-daipen] (3) as a catalyst afforded secondary alcohol 2 quantitatively and in 99.4% ee. Further exploration of the effect of the thiazole ring substitution revealed that the catalyst was highly effective for the enantioselective hydrogenation of 5-benzoyl thiazoles, which afforded corresponding alcohols in 92-99% ee. The same protocol was applicable to a variety of aromatic-heteroaromatic ketones to generate secondary alcohols in excellent enantioselectivities. [reaction: see text] 相似文献
139.
Electrospray ionization mass spectrometry (ESI-MS) is used to evaluate the metal binding selectivities of an array of novel caged macrocycles for silver, gold, copper, nickel, zinc, iron, lead, manganese and alkali metal ions. It is found that five of the new compounds display silver selectivity, and their relative affinities for various metals depend on the type, number, and arrangement of heteroatoms (N, O), the cavity size, and the presence of aromatic substituents. Alkali metal cation binding studies are used to evaluate the size-selectivities of the cavities of the macrocycles. Electronic structure calculation by B3LYP density function theory methods were used to model the metal complexes. The presence of nitrogen atoms in the macrocyclic ring is essential for silver selectivity over other transition metals and alkali metal ions, and the presence of aromatic groups also enhances silver avidity. Macrocycle 3, a triaza-18-crown-6 analog modified with two phenyl groups and a cage group, is capable of selective extraction of Ag+ from aqueous solutions in the presence of other transition metal ions and the most common alkali and alkaline earth metal ions. 相似文献
140.
Scott J Gambarotta S Korobkov I Budzelaar PH 《Journal of the American Chemical Society》2005,127(37):13019-13029
The alkylation of the Brookhart-Gibson {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)} FeCl2 precatalyst with 2 equiv of LiCH2Si(CH3)3 led to the isolation of several catalytically very active products depending on the reaction conditions. The expected dialkylated species {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2}(C5H3N)Fe(CH2SiMe3)2 (2) was indeed the major component of the reaction mixture. However, other species in which alkylation occurred at the pyridine ring ortho position, {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2-2-CH2SiMe3}(C5H3N)Fe(CH2SiMe3) (1), and at the imine C atom, {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC(CH3)(CH2 SiMe3)](C5H3N)}Fe(CH2SiMe3) (3), have also been isolated and fully characterized. In addition, deprotonation of the methyl-imino functions and formation of a new divalent Fe catalyst {[2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}Fe(mu-Cl)Li(THF)3 (4) also occurred depending on the reaction conditions. In turn, the formation of 4 might trigger the reductive coupling of two units through the methyl-carbon wings. This process resulted in the one-electron reduction of the metal center, affording a dinuclear Fe(I) alkyl catalyst {[{[2,6-(i-Pr)2C6H5]N=C(CH3)}(C5H3N){[2,6-(i-Pr)26H5]N=CCH2}Fe(CH2SiMe3)]}2 (5). Different from other metal derivatives, complex 5 could not be prepared from the monodeprotonated version of the ligand. Its reaction with a mixture of FeCl2 and RLi afforded instead [{2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}FeCH2Si(CH3)3][Li(THF)4] (6) which is also catalytically active. All of these high-spin species have been shown to have high catalytic activity for olefin polymerization, producing polymers of two distinct natures, depending on the formal oxidation state of the metal center. 相似文献