Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Abstract Aus dem Diol (I) werden Makrocyclen (III) hergestellt, die sauer oder bei katalytischer Hydrierung zu Diolen (IV) gespalten und dann weiter zu den spirocyclischen Makroethern (V) kondensiert werden.
Abstract Oligoethylene glycols and some related alcohols were efficiently tosylated with p-toluenesulfonyl chloride in a tetrahydrofuran–water (1:1) mixture in the presence of excess sodium hydroxide. This method is advantageous over the conventional tosylation in pyridine both regarding the work-up procedure, the yield, and the purity of the product, and may be potentially useful for the tosylation of certain acid-labile alcohols.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular design of crown ethers. 4. Syntheses and selective cation binding of 16-crown-5 and 19-crown-6 lariatsMikio Ouchi, Yoshihisa Inoue, Kazuhito Wada, Shinichi Iketani, Tadao Hakushi, and Edwin WeberCite this: J. Org. Chem. 1987, 52, 12, 2420–2427Publication Date (Print):June 1, 1987Publication History Published online1 May 2002Published inissue 1 June 1987https://pubs.acs.org/doi/10.1021/jo00388a016https://doi.org/10.1021/jo00388a016research-articleACS PublicationsRequest reuse permissionsArticle Views1468Altmetric-Citations73LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Abstract Calorimetric titrations have been performed in anhydrous acetonitrile at 25°C to give the complex stability constants (K s) and the thermodynamic parameters (ΔGΔ, ΔHΔ and ΔSΔ) for the complexation of light lanthanoid(III) nitrates (La-Gd) with N-benzylaza-21-crown-7 3. Data analyses, assuming 1:1 stoichiometry, were successfully applied to all light lanthanoid-azacrown ether combinations employed. Using the present and previous data on 15- to 21- membered N-benzylazacrown ethers 1–3, the effect of ring size upon complexation behavior was discussed comparatively and globally from the thermodynamic point of view. The complexation behaviors are analyzed in terms of the size-fit concept, N-substituent coordination numbers, and lanthanoid's surface charge density. Thermodynamically the complexation of light lanthanoids with azacrown ethers is enthalpy-driven, while the cation selectivity is generally entropy-driven in acetonitrile.
The extraction of bitumen from Athabasca tar sand by a combined solvent-aqueous-surfactant (cold-water) method at 25±3 C and neutral pH offers many advantages over the present extraction technology which utilizes high pH at 80 C. Foremost of these are reduced energy requirements and reduced clay-sludge disposal problems. Any cold-water extraction scheme avoiding these problems with surfactants depends on surfactant selection criteria. To date, few systematic studies of the relations between measurable surfactant properties and the extraction of bitumen from tar sand have been performed. In this work, the relations between bitumen extraction in a solvent-aqueous-surfactant test system and the properties of the surfactant solution have been measured for a series of octyl and nonyl-phenyl-poly-(ethosy)-ethanol surfactants. The surfactant properties measured included surface, interfacial and spreading tensions, partition coefficients and HLB (hydrophillic-lipophyllic balance). Optimal bitumen extraction with these surfactants depended not only on surfactant properties but also on the details of the extraction process. When used in aqueous solution, optimal extraction occurred at spreading tensions of 10—20 dynes/cm, and at HLB values of 7. Adhesion tensions between pyrophyllite and aqueous solutions of Tween surfactants are linearly correlated to bitumen recovery by both aqueous-surfactant and solvent-aqueous-surfactant extraction methods. This appears to be the first linear correlation between surfactant properties and the extraction of bitumen from tar sand which has been observed.
anti-1,4,5,8-Tetrapropyl-1,4:5,8-diepoxyanthracene has been synthesized and structurally characterized by X-ray crystallography. This compound crystallizes in monoclinic space group P21/c with cell parameters a = 10.166(1)Å, b = 10.9186(8)Å, c = 10.640(1)Å, β = 112.464(4)°, and Z = 2. The crystal structure was solved by direct methods and refined by full-matrix least squares to a final R value of 0.054 for 2385 reflections (I > 2.00 σ(I)).
Complex stability constants and thermodynamic parameters have been determined for the complexation of alkali metal ions with large-sized crown ethers, i.e. 24-crown-8 to 36-crown-12, in methanol at 25 °C. Using the present and reported data, the complexation behaviour of 12-crown-4 through 36-crown-12 is discussed comparatively and globally from the thermodynamic point of view, complex stability sequence for each cation as a function of ring size shows a characteristic two-peak profile with a global maximum and a smaller local maximum at a larger ring size, both of which may be interpreted in terms of the size-fit concept. Thermodynamically, the complexation of alkali metal ions with the crown ethers is absolutely enthalpy-driven in methanol, but the cation selectivity determined by the size–fit relationship is shown to be mostly entropy-governed. The large, but ring size insensitive, enthalpy and entropy changes for large crown ethers are rationalized by the mutually resembling cation–ligand interaction, degree of desolvation, and substantial structural freezing upon encapsulating complexation forming a highly flexible 3D cavity. However, the size–fit concept still appears to play a subsidiary role even in the complexation by larger crown ethers, although its control becomes fairly loose.
