Difference in micellar properties of sodium dodecyl sulfonate from sodium 4-decyl naphthalene sulfonate in D2O solution studied by 1H NMR relaxation and 2D NOESY

¹H chemical shift changes of sodium 4-decyl naphthalene sulfonate (SDNS) at 313 K show that its critical micellar concentration lies between 0.82 and 0.92 mmol/dm³, which is in the same range as that of the previous study at 298 K. The spin–lattice relaxation time, spin–spin relaxation time and two-dimensional nuclear Overhauser enhancement spectroscopy experiments give information about the structure of the SDNS micelle and the dynamics of the molecules in the micelle. The size of the SDNS micelle remains almost unchanged in the temperature range from 298 to 313 K as deduced by analyzing the self-diffusion coefficient. Special arrangement of the naphthyl rings of SDNS in the micelles affects the packing of these hydrophobic chains. The methylene groups of the alkyl chain nearest the naphthalene groups penetrate into the aromatic region, which results in a more tightly packed hydrophobic micellar core than that of sodium dodecyl sulfonate.     

Crystallization-induced asymmetric transformation. Application to conjugate addition of benzylamine to amides of benzoylacrylic acid

Adducts of the conjugate addition of benzylamine to enantiopure amides of aroylacrylic acid possess high enantiomeric and diastereomeric purity. A high degree of stereoselectivity has been achieved by means of crystallization-induced asymmetric transformation. A practical synthesis leading to dipeptides containing homophenylalanine is depicted.     

Efficient synthesis of ferrocenylenones by Friedel-Crafts acylation with EtAlCl2-Me3Al

Efficient synthesis of ferrocenylenones using a Friedel-Crafts acylation reaction is described. Acryloyl, methacryloyl, crotonoyl, cinnamoyl, and β-methylcrotonoyl chlorides react with ferrocene in the presence of a Lewis acid (EtAlCl₂ or EtAlCl₂-Me₃Al) to give the corresponding ferrocenylenones (acryloyl, methacryloyl, crotonoyl, cinnamoyl, and methylcrotonoylferrocenes) in good isolated yields. Besides ferrocenylenones, chloroactylferrocene is also synthesised by this method.     

Reaction of silyl ketene acetals with epoxides: a new method for the synthesis of γ-butanolides

Titanium tetrachloride promoted reaction of silyl ketene acetals with epoxides, followed by acidic work-up, affords butanolides in moderate/good yields. With epihalohydrins the reaction is regioselective and occurs at the less substituted end of the epoxide; the γ-haloalkyl-γ-butanolides thus obtained can be further transformed into various products.     

Influence of the H/F replacement on the homoaromaticity of homotropylium ion: a GIAO/DFT theoretical study

The problem of homoaromaticity in mono-, di- and polyfluorinated- homotropylium cations is addressed by the B3LYP/6-311++G** DFT method. The energetic, structural and magnetic criteria are used for this purpose. They convincingly show that the ground state equilibrium species are aromatic, or in other words that the homoaromaticity is preserved by the (poly)fluorination. In contrast, a considerable decrease in the aromatic stabilization is observed in the transition structures (TS). According to the NICS(0) index, they vary form strongly antiaromatic, via weakly and non-aromatic to slightly aromatic transition states. However, the hierarchy of the aromaticity in fluorinated homotropylium ions predicted by NICS(0) is completely unrelated to that obtained by using the energy criterion assuming a kinetic definition of aromaticity. On the other hand the latter is closely related to geometric parameters of the equilibrium and transition structures.     

宜产葛根中微量元素含量的测定

原子吸收分光光度法测定了宜昌地区产葛根中的Cu．Fe．Zn、Mn、Mo．Mg、Se等6种微量元素。为葛根的药效进一步研究和综合开发利用提供了新的科学依据。     

Effect of nonstoichiometry on Raman scattering of VO2 films

We report on Raman scattering of VO2 films prepared by radio frequency magnetron sputtering under different conditions. Our investigations revealed that the dominated Raman peaks shift towards high frequency for both V-rich and O-rich VO2 films, compared with the stoichiometry VO2 films. The experimental evidence is presented and the cause for nonstoichiometry dependence of Raman spectra of VO2 films is discussed.     

Crystallographic report: Crystal structure of a one‐dimensional zinc(II) coordination polymer containing 4,4′‐biphenyldicarboxylate hemihydrate

A one‐dimensional zinc(II) coordination polymer has been constructed from zinc(II), 4,4′‐biphenyldicarboxylate and pyridine in which each zinc(II) atom is coordinated by two pyridine ligands and two monodentate 4,4′‐biphenyldicarboxylate ligands that define a distorted tetrahedral geometry. Copyright © 2003 John Wiley & Sons, Ltd.