Electrochemical intercalation of lithium into graphitized carbons

The change of the carbon structure with electrochemical intercalation of lithium has been investigated by X-ray diffraction (XRD) method. Graphitized carbons showed the first and the second stage structures clearly during the intercalation process. However, the layer spacing corresponding to the 1st stage structure of graphitized carbon was smaller than that of graphite. This is because the first stage structure of graphitized carbon is the mixed structure of lithiated graphite crystallites and lithiated turbostratic disordered layers. The lithium is mainly intercalated into turbostratic disordered layers above 0.1 V versus Li/Li⁺, and intercalated into graphite crystallites rather than turbostratic disordered layers below 0.1 V versus Li/Li⁺.     

Angular dependence of 1H- and 2H-NMR spectra of water and methanol absorbed in cellulose triacetate film

¹H- and ²H-NMR spectra of water (H₂O and D₂O) and methanol (CH₃OD and CD₃OH) absorbed in cellulose triacetate films have been observed as a function of the angle θ between the film surface and the magnetic field. ¹H-NMR signals of H₂O and CH₃OD are doublets and triplets due to dipole interactions, respectively. ²H-NMR signals of D₂O, CD₃OH, and CH₃OD are doublets due to quadrupole splittings. The magnitudes of these splittings change depending on θ. The analysis of the angle-dependent patterns indicates that the motionally averaged axes of the dipole and the quadrupole moments orient in the direction perpendicular to the film surface. The alignment of water and/or methanol molecules originates from the film morphology, which is anisotropic in the perpendicular direction. From the angle dependence of the chemical shift, the volume diamagnetic susceptibility of the film is estimated to be 0.44 ppm.     

An Efficient Stereoselective Synthesis of (±)-Sweroside and (±)-secologanin aglucone O-methyl ethers. Preliminary communication

A seven-step stereoselective synthesis of (±)-sweroside aglucone O-methyl ether ( 16a ) was achieved in 27% overall yield from 1, 4-cyclohexadiene ( 4 ) and methyl diformylacetate ( 5 ). Secologanin aglucone O-methyl ether ( 18a ) was then formed from 16a in 90% overall yield by a straightforward process. The key step in the synthesis was a [2+2]-enone-photoannelation of 4 and 5 to form the key intermediate 6 which possessed the desired cis-fused ring configuration, and all the caron atoms needed to complete the synthesis of 16a and 18a .     

New diarylheptanoids from Alnus japonica and their antioxidative activity

In the course of research on the bioactive constituents of woody plants in the Cyugoku area of Japan, a methanol extract of the leaves of Alnus japonica were found to have strong antioxidative activity. Ethyl acetate soluble and n-buthanol soluble fractions of the methanol extract had a potent antioxidative effect. Both fractions were purified by silica gel column chromatography and HPLC using an ODS column to give four new diarylheptanoids along with known diarylheptanoids and flavonoids. These new compounds were elucidated to be 7-(3,4-dihydroxyphenyl)-5-hydroxy-1-(4-hydroxyphenyl)-3-heptanone-5-O-beta-D-xylopyranoside (1), 1-(3,4-dihydroxyphenyl)-5-hydroxy-7-(4-hydroxyphenyl)-3-heptanone-5-O-beta-D-xylopyranoside (2), 1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxy-3-heptanone-5-O-[2-(2-methylbutenoyl)]-beta-D-xylopyranoside (3) and 1,7-bis-(3,4-dihydroxyphenyl)-5-methoxy-3-heptanone (4) using spectral methods and especially 1H-, 13C-NMR and 2D-NMR measurements. The isolated compounds including their main constituent, oregonin (5), were tested for antioxidative activity. Some of these compounds having two catechol structures showed potent antioxidative activity. Compounds having one catechol structure showed moderate antioxidative activity, but a peracetate of 5 having no catechol structure exhibited no antioxidative activity. Thus the catechol structure of the diarylheptanoids is indispensable for antioxidative activity.     

Aromatic constituents from the heartwood of Santalum album L

A phytochemical investigation of the polar constituents in the heartwood of Indian Santalum album L. resulted in the isolation of three new neolignans (1-3) and a new aromatic ester (4), along with 14 known components. The structures of the new compounds (1-4) were established using spectroscopic methods.     

Spectrophotometric determination of micro amounts of cationic polymeric flocculants by flow injection analysis

Cationic polymeric flocculants in water are determined spectrophotometrically with the anionic compound 3-(2-hydroxy-3-carboxyanilide-1-azonaphthalene)-4-hydroxybenzenesulfonic acid at pH 10 by flow injection analysis. The calibration graph at 680 nm is rectilinear from 0 to 20 mg l^?1 under optimal conditions. The relative standard deviation for 20 injections of Cat-Floc (10 mg l^?1) was 1.2%; the sample throughput was 60 h^?1.     

Theoretical investigation on electron transport through an organic molecule: effect of the contact structure

Knowing how the contact geometry influences the conductance of a molecular wire junction requires both a precise determination of the molecule/metallic-electrode interface structure and an evaluation of the conductance for different contact geometries with a fair accuracy. With a greatly improved method to solve the Lippmann-Schwinger equation, we are able to include at least one atomic layer of each electrode into the extended molecule. The artificial effect of the jellium model used for the electrodes is therefore significantly reduced. Our first-principles calculations on the transport properties of a single benzene dithiolate molecule sandwiched between Au(111) surfaces show that the transmission of the bridge site contact, which is the most stable adsorption configuration in equilibrium, displays different features from those of other configurations, and that the inclusion of the surface layers of Au electrodes into the extended molecule shifts and broadens the transmission peaks due to a stronger and more realistic S-Au bonding. We discuss the geometry dependence of the transport properties by analyzing the density of states of the molecular orbitals.     

Fern constituents: triterpenoids from Adiantum capillus-veneris

Two new migrated hopane triterpenoids, viz. 4alpha-hydroxyfilican-3-one and fern-9(11)-en-12beta-ol, and olean-18-en-3-one and olean-12-en-3-one as the first example of oleanane compounds from Adiantum ferns were isolated along with many other known triterpenoids from Adiantum capillus-veneris of China and Egypt. Their structures were elucidated by spectroscopic analyses.     

2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl-beta-cyclodextrin, a useful stationary phase for gas chromatographic separation of enantiomers

Heptakis(2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (2,3-MOM-6-TBDMS-beta-CD), synthesized by using methoxymethylchloride (MOM-Cl) as derivatization reagent, was used for capillary gas chromatographic separation of enantiomers. The new chiral stationary phase proved to be suitable for the enantiodifferentiation of volatiles from various chemical classes. Compared to the corresponding gamma-CD derivative (2,3-MOM-6-TBDMS-gamma-CD), the spectrum of compounds for which enantiomers could be separated was more limited and the enantioseparation achieved was generally less pronounced. Unusually high separation factors were observed for 2-alkyl esters of short chain acids (C2-C6). Phenomena underlying the enantioseparation of 2-pentyl acetate (alpha: 4.31; 35 degrees C) were investigated by determining thermodynamic parameters. Data show that only one enantiomer is retained significantly on the chiral stationary phase whereas the other one behaves like the hydrocarbons used as references.