Circular dichroism spectra of the inclusion complexes of phlorizin in cyclodextrins

Two aromatic rings of a phlorizin molecule form inclusion complexes with -CD and -CD. Induced circular dichroism spectra of these complexes have been measured to estimate the orientation of the two aromatic rings in the hydrophobic space of CDs. Apparent complex formation constants have been also estimated for each complex. It is concluded that phlorizin forms a stronger inclusion complex with -CD than with -CD.     

Development of an efficient method for preparation of 1,3,5-trihydroxyisocyanuric acid (THICA) and its use as aerobic oxidation catalyst

1,3,5-Trihydroxyisocyanuric acid (THICA), which serves as an efficient radical-producing catalyst from hydrocarbons, was successfully prepared by two methods. The reaction of O-benzylhydroxyamine with phenyl chloroformate gave formbenzyloxycarbamic acid phenyl ester of which subsequent treatment with dimethylaminopyridine (DMAP) produced 1,3,5-tribenzyloxyisocyanurate leading to THICA by hydrogenation with H₂ on Pd/C. The other method involved the direct synthesis of 1,3,5-tribenzyloxyisocyanurate from O-benzylhydroxyamine and diphenyl carbonate. The aerobic oxidation of p-methylanisole catalyzed using THICA as a key catalyst afforded p-anisic acid in almost quantitative yield (>99%).     

Large-scale separation of metallic and semiconducting single-walled carbon nanotubes

In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way.     

Effect of Organic Ligands Used in Sol-Gel Process on the Formation of Mullite

The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate (TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)₂(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG>PD>MPD. When Al(OBu)₂(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG>BD>DEME>MPD. Between the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)₂(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility between the silica and alumina.     

Effects of protonation on the thermodynamic properties of alkyl dimethylamine oxides

The effects of protonation on alkyldimethyl amine oxide micelles are reviewed, mainly with regard to dodecyl and tetradecyl homologs. The topics discussed are hydrogen ion titration properties, critical micelle concentration (CMC), area per surfactant and micelle aggregation number. A hydrogen bond hypothesis is proposed to interpret the several characteristic results associated with protonation: between two cationic species as well as between the non-ionic-cationic pair. The dipole-dipole interaction of the non-ionic micelle is discussed in relation to both: (a) the unusually high CMC values of the non-ionic micelles compared with other non-ionic surfactants with the same hydrocarbon chain; and (b) the reversal of the stability of the non-ionic and the cationic micelles at high ionic strengths. Two different approaches of the salting out effect on the ionic micelles are compared, the Chan-Mukerjee approach and ours, in relation to the non-linear Corrin-Harkins relation. The obtained salting out constants of the surfactants carrying a dodecyl chain decreased as the head group becomes more polar. Infrared and 13C-NMR spectra data are examined from the point of the specific interaction claimed by the hydrogen bond model. Mixed surfactant systems including amine oxides and the solid state phase behavior of amine oxides are both briefly reviewed.     

On-column derivatization-capillary electrochromatography with o-phthalaldehyde/alkylthiol for assay of biogenic amines

The elution behaviors of the biogenic amines, histamine (HA) and its metabolite methyl histamine (MHA), were evaluated by means of on-column derivatization (OCD)-capillary electrochromatography (CEC) which employed a monolithic octadecylsilica (ODS) capillary column (20 cm of effective length x 50 microm of inner diameter). Five kinds of alkylthiols, e.g., 2- hydroxyethylthiol (or 2-mercaptoethanol (2-ME)), ethanethiol (ET), 1-propanethiol (1-PT), 2-methyl-1-propanethiol (2-MPT) and 1-butanethiol (1-BT) were separately presented at 5 mM each in the OCD-CEC separation run buffer consisting of 60% acetonitrile in 5 mM o-phthalaldehyde (OPA)-10 mM borate buffer (pH 10). When 2-ME was present in the run buffer solution, both derivatives corresponding to HA and MHA migrated separately, but closely together through the capillary column. Replacement of 2-ME with 1-BT in the run buffer solution caused a delay in their elution profiles on the electrochromatogram and the separation between those two peaks became remarkably improved. The elution times of HA and MHA followed the increase in alkyl chain length or hydrophobicity of thiol, 1-BT > 2-MPT > 1-PT > ET > 2-ME. Performance of on-line preconcentrations of HA and MHA was also evaluated by varying the electrokinetic injection voltage from 1 kV to 8 kV. The peak area counts corresponding to HA recorded about 50 times higher when 2 kV was applied for 240 s to a 0.1 mM HA solution than when 8 kV was applied for 5 s. This method was next applied to a sample of human urine spiked with HA and MHA at levels of 0.1 microM each. Although HA and MHA peaks were not identifiable among the peaks corresponding to the materials in the urine matrix when OPA/2-ME was employed in a run buffer for the OCD-CEC, the separation and identification of their peaks became possible by replacing 2-ME with 1-BT in the run buffer solution.     

Microcolumn ion chromatography with conductimetric detection

Summary A miniaturized flow cell for an electrical conductivity detector has been made and applied to the ion chromatography of inorganic anions. It consisted of stainless steel tubes (0.13 mm ID×0.31 mm OD) and PTFE tubes (0.25 mm ID×2 mm OD). The detection limit for chloride at S/N=3 was 36 pg or 0.33 ppm for a 0.11 l injection.     

Raman spectra of stilbene negative ions in tetrahydrofuran solution

Raman spectra of stilbene mono- and di-negative ions in tetrahydrofuran solution were obtained by Ar⁺ laser exciting lines. A considerable frequency shift was observed for several vibrations in the successive steps: stilbene → (stilbene)^? → (stilbene)^2?. The observed shift is discussed in a simple VB scheme, particularly in comparison with the results on anthracene negative ions. The resonance Raman effect was striking for both ions with intensity maxima at the exciting wavelengths close to the absorption maxima.     

Thermoanalytical studies on specialty polymers in Japan

Thermoanalytical studies on specialty polymers in Japan are reviewed. The basic and applied researches for the developments of new specialty polymers such as high-performance polymers, liquid crystalline polymers, and biodegradable polymers during the 1990's are introduced from the standpoint of thermal analysis. Many studies were performed for the improvements of durability and thermal stability of engineering polymers, biodegradable polymers and so on. A special topic of researches on the thermal behavior of polymers by high-pressure differential thermal analysis is included in this review. This revised version was published online in July 2006 with corrections to the Cover Date.