Search results for "AIC"
showing 10 items of 2470 documents
ChemInform Abstract: A Novel Synthesis of Chain-Extended Amino Sugar Derivatives Through Aza-Cope Rearrangement of N-Galactosyl-N-homoallylamines.
2010
Abstract Chain-extended amino sugars are synthesized via stereocontrolled Lewis acid-catalyzed aza-Cope rearrangement of N-glycosyl homoallylamines in high yield and stereoselectivity.
A novel synthesis of chain-extended amino sugar derivatives through aza-Cope rearrangement of N-galactosyl-N-homoallylamines
1998
Abstract Chain-extended amino sugars are synthesized via stereocontrolled Lewis acid-catalyzed aza-Cope rearrangement of N-glycosyl homoallylamines in high yield and stereoselectivity.
Amphiphilic Polyethers of Controlled Chain Architecture
2003
The amphiphilic polymers, polymers which contain in their macromolecules both hydrophilic and hydrophobic units1, are the base for valuable materials due to their diversified interaction with liquids. So they may act as emulsifiers, compatibilizers, “smart” materials (responding to external stimuli)2 and many others. In order to control their properties, the hydrophilic — hydrophobic balance in the macromolecules has to be controlled. This balance depends not only upon the constitution of the chain repeating units, but also upon the art of their distribution in the chains (copolymers of controlled unit sequences), the chain topology, the size of the chains and many others. So a careful engi…
Complexes of Azelaic and Diethylenetrioxydiacetic Acids with Na+, Mg2+, and Ca2+ in NaCl Aqueous Solutions, at 25 °C
1999
Formation constants of Na + , Mg 2+ , and Ca 2+ complexes of azelaic and diethylenetrioxydiacetic acids have been determined by potentiometry (H + -glass electrode) at different ionic strengths (0 ≤ I ≤ 1 mol dm -3 ), at t = 25 °C. For all the systems the species ML and MHL have been found. The relative formation constants are reported together with the parameters for the dependence on ionic strength. Results are discussed in comparison with those for other carboxylic ligands. Speciation problems are considered also.
Separation of homologues and isomers of linear alkylbenzenesulfonates by capillary electrophoresis with sodium dodecyl sulfate, carboxylic acids and …
2003
The ability of several anionic compounds, including carboxylic and dicarboxylic acids, sodium dodecyl sulfate (SDS), and sodium deoxycholate (SDC) and other bile salts, to separate the C(10)-C(13) homologues and the corresponding 20 positional isomers of linear alkylbenzenesulfonates (LAS) by capillary electrophoresis was studied. Up to 19 peaks and a shoulder were observed with a background electrolyte (BGE) containing 10 mM phosphate (pH 6.8), 30% acetonitrile and 40 mM SDS, and 18 peaks were obtained with a BGE containing 10 mM borate (pH 9), 40% ethanol and 40 mM palmitic acid (PA). Resolution increased with the alkyl chain length of the carboxylic acid. Dicarboxylic acids with a short …
Controlling the dimensionality of oxalate-based bimetallic complexes: The ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞(18-crown-6=C12H24O6,…
2007
Abstract The bimetallic ferromagnetic chain {[K(18-crown-6)][Mn(bpy)Cr(ox)3]}∞ (1) has been synthesized and characterized. It crystallizes in the orthorhombic chiral space group P212121 [a = 9.0510(2) A, b = 14.4710(3) A, c = 26.8660(8) A, V = 3510.97(1) A3, Z = 2]. Compound 1 is made up by anionic [Mn(bpy)Cr(ox)3]− 1D chains and cationic [K(18-crown-6)]+ complexes. The magnetic exchange within the chain is ferromagnetic [J = +7.8(7) cm−1]. In the solid state, the ferromagnetic chains are well isolated magnetically and no long range magnetic ordering has been observed above 2 K.
ChemInform Abstract: Reactions of the Hydrofluoroborate Salts of Open-Chain Analogues of Reissert Compounds with Some α,β-Ethylenic Esters.
2010
The reaction of the hydrofluoroborate salt of an open-chain analogue of a Reissert compound with some α,β-ethylenic esters does not give a [4 + 2] cycloadduct, as previously described in the case of ethyl acrylate. The reaction starts with a 1,3-dipolar cycloaddition of a munchnone imine 5c, d. The [3 + 2] cycloadducts 13 evolve via a rearrangement–condensation sequence to give a substituted 2-pyridone derivative 18 or 19. The proposed mechanism has been verified by the isolation and structural X-ray analysis of some compounds of the reaction sequence.
Study of binding media in works of art by gas chromatographic analysis of amino acids and fatty acids derivatized with ethyl chloroformate
1997
The aim of this work is to identify proteinaceous and oil binding media used in paintings from art collections in the Region of Valencia (Spain). This information is extremely useful for conservation and restoration work. The proposed procedure involves protein and glyceride hydrolysis from sub-milligram samples by treatment with hydrochloric acid, followed by neutralization, partition with chloroform and derivatization with ethyl chloroformate (ECF) of both the aqueous and the organic phases. The ECF derivatives of amino acids and azelaic, myristic, palmitic and stearic acids are separated by capillary gas chromatography. Amino acids are mainly found in the aqueous phase and long chain fat…
Contour-Variable Model of Constitutive Equations for Polymer Melts
2009
Based on a modified expression of the rate of the convective constraint release, we present a new contour-variable model of constitutive equations in which the non-uniform segmental stretch and the non-Gaussian chain statistical treatment of the single chain are considered to describe the polymer chain dynamics and the rheological behavior of an entangled system composed of linear polymer chains. The constitutive equations are solved numerically in the cases of steady shear and transient start-up of steady shear. The results indicate that the orientation and stretch, as well as the tube survival probability, have strong dependence on the chain contour variable, especially in the high-shear-…
Deuteron NMR Relaxation Studies of Combined Main-Chain/Side-Chain Polymers in the Liquid Crystalline and Glassy State
1989
Etude du polymere [O−Ph−CO 2 −Ph(R)−O−CO−Ph−O-(CH 2 ) 10 −] n (R=(CH 2 ) 6 −O−Ph−N=N−Ph−OMe) qui est caracterise par des parametres d'ordre des mesogenes de la chaine principale tres superieurs a ceux des chaines laterales. On observe une biaxialite moleculaire dans toutes les mesophases et dans la phase smectique A