Synthesen von Heterocyclen, 121. Mitt.: Chinolizine und Indolizine V: Eine Synthese von 4-Methyl-2-chinolizinonen

Zusammenfassung Die Reaktion von 2-Pyridylessigsäurederivaten (1a, 1b) mit Diketen (2) in sied. Eisessig liefert in 1-Stellung substit. 4-Methyl-2-chinolizinone.

---

Syntheses of heterocycles, CXXI: Quinolizines and indolizines. A synthesis of 4-methyl-2-quinolizinones

The reaction of 2-pyridylacetic acid derivatives (1a, 1b) with diketene (2), gives 4-methyl-2-quinolizinones.

     

Synthesen von Heterocyclen, 108. Mitt.: Über Reaktionen mit Salicylsäurechlorid

Zusammenfassung Salicylsäurechlorid (1) reagiert mit Campherimin ·HCl bzw. Campheranil oder mit Aldazinen zu Derivaten des 1,3-Benzoxazin-4-ons.

---

Salicoyl chloride reacts with camphorimine hydrochloride and camphoranile or with aldazines to give derivatives of 1.3-benzoxazin-4-ones.

     

Quarter wave plates for submillimeter wavelengths

A review is given of different types of quarter wave plates as presently used in the optical and microwave spectral range, with a view to their application in the sub-mm wave-length range. Two types of quarter wave plates have been constructed and results of measurements at 640m are given.     

2-Amino-4-bromobutanoic Acid

(2S)- and (2R)-2-Amino-4-bromobutanoic acid were prepared starting from N-Boc-glutamic acid α tert-butyl ester. The double tert-butyl protection was necessary to prevent a partial racemisation during Barton’s radical decarboxylation used to transform the γ-carboxylic group into a bromide. This bromide reacted with different nitrogen, oxygen and sulphur nucleophiles to give nonnatural amino acids characterised by basic or heterocyclic side chains. The title compound was also used to prepare a conformationally constrained peptidomimetic.     

A molecular mechanics approach for analyzing tensile nonlinear deformation behavior of single-walled carbon nanotubes

In this paper, by capturing the atomic information and reflecting the behaviour governed by the nonlinear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes (SWCNT’s) is established to describe the nonlinear stress-strain curve of SWCNT’s and to predict both the elastic properties and breaking strain of SWCNT’s during tensile deformation. An analysis based on the virtual internal bond (VIB) model proposed by P. Zhang et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an acceptable analytical method for analyzing the mechanical behavior of SWCNT’s. The project supported by the National Natural Science Foundation of China (10121202, 90305015 and 10328203), the Key Grant Project of Chinese Ministry of Education (0306) and the Research Grants Council of the Hong Kong Special Administrative Region, China (HKU 7195/04E).     

Dielectric relaxation in vitreous metaphosphates at medium temperatures

Dielectric relaxation experiments were carried out on mixed alkali metaphosphate glasses between room temperature and about 300°C (f = 10³ s^?1). The observed relaxations appeared to be connected with the movement of the alkali ions from site to site. By using stainless steel electrodes it was possible to reveal a relaxation peak free from conduction losses and due only to the migration from site to site of the cations. When two cations of dissimilar sizes are simultaneously present a mixed alkali effect was observed, i.e. an unproportionally large reduction in the alkali ion mobilities. It is shown that this effect can be at least partly explained by considering the changes in the potential energy states upon mixing dissimilar cations due to polarizing forces and coulombic interactions.     

Preparation of nano-hydroxyapatite/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) biocomposite microspheres

Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water (s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and transmission electron microscopy (TEM).     

Trace-Level Determination of Phenol by Liquid Chromatography with On-Line Precolumn Technology and Fluorescence Detection

Abstract

A strongly basic anion-exchange resin is used for the trace enrichment and automated sample handling of phenol, with subsequent determination by reversed-phase liquid chromatography with fluorescence detection. Because of the presence of high concentrations of ionic compounds in the water samples tested, phenol is first trapped on a relatively long precolumn filled with a highly hydrophobic packing material; during this step, (in) organic anions which are not retained, are flushed to waste. In the next step, phenol is desorbed from this column at high pH and sorbed in a small zone (“peak compression”) on a short precolumn containing the anion exchanger.

In the analysis of tap and river water samples, the detection limit was found to be 10ppt (1:10¹¹).