Synthesis of optically active 6-substituted 2-(aminomethyl)chromans

Three novel, optically active, 6-substituted 2-(aminomethyl)chromans were synthesized from readily available chroman 2-carboxylic acid precursors. These chroman-containing primary amines are useful building blocks for the synthesis of chroman-derived pharmaceutical agents.     

Introduction to Session 5

Applied Biochemistry and Biotechnology -     

Expedient synthesis of substituted imidazoles from nitriles

Expedient and practical new methodology for the synthesis of substituted imidazoles was developed to provide a rapid access to a variety of 2-substituted, 1,2-disubstituted and 1,2,4-trisubstituted imidazoles by the direct CuCl-mediated reaction of nitriles with α-amino acetals in an intermolecular as well as intramolecular fashion.     

Electroreduction of Aryldiazonium Ion at the Polar and Non-Polar Faces of ZnO: Characterisation of the Grafted Films and Their Influence on Near-Surface Band Bending

ZnO is a strong candidate for transparent electronic devices due to its wide band gap and earth-abundance, yet its practical use is limited by its surface metallicity arising from a surface electron accumulation layer (SEAL). The SEAL forms by hydroxylation of the surface under normal atmospheric conditions, and is present at all crystal faces of ZnO, although with differing hydroxyl structures. Multilayer aryl films grafted from aryldiazonium salts have previously been shown to decrease the downward bending at O-polar ZnO thin films, with Zn−O−C bonds anchoring the aryl films to the substrate. Herein we show that the Zn-polar (0001), O-polar (000 ), and non-polar m-plane (10 0) faces of ZnO single crystals, can also be successfully electrografted with nitrophenyl (NP) films. In all cases, X-ray photoelectron spectroscopy (XPS) measurements reveal that the downward surface band bending decreases after modification. XPS provides strong evidence for Zn−O−C bonding at each face. Electrochemical reduction of NP films on O-polar ZnO single crystals converts the film to a mainly aminophenyl layer, although with negligible further change in band bending. This contrasts with the large upward shifts in band bending caused by X-ray induced reduction.     

The role of surface oxides in formic acid oxidation on Au

Compared to Pt or Pd electrodes, Au is a poor catalyst for the direct anodic oxidation of HCOOH, but the formation of Au surface oxides in acidic solutions is accompanied by a fast oxidation of HCOOH. This fast reaction is not simply a secondary reaction of Au surface oxides since those oxides are kinetically stable in HCOOH solutions. They do oxidize HCOOH only via a slow and purely electrochemical process which occurs on free Au sites and is “driven” by oxide reduction. The fast HCOOH oxidation is due to a highly reactive intermediate which is able either to form stable Au oxides Au_nO_m or to react with HCOOH. Our results are consistent with the model that by the charge transfer step a reactive non-equilibrium {Au…O> species is formed which converts to stable equilibrium oxides Au_nO_m after migration and rearrangement steps. Pre-equilibrium <Au…O> oxidizes HCOOH and this oxidation is of lower order with respect to <Au…O> compared with the formation of Au_nO_m.     

Graphite furnace atomic absorption spectrometric determination of ruthenium in iron meteorites

A procedure for the determination of ruthenium in iron meteorites involves its oxidation to RuO₄ by sodium periodate in hydrochloric acid and extraction of the tetroxide into chloroform. Various parameters of the method were studied: sample dissolution, optimum amount of oxidant, shaking time, distribution ratio and stability of the complex. The relative standard deviation assessed from replicate analyses of the North Chile iron meteorite was 6.6%. There are no certified standards for iron meteorites, but the value of 20.0 μg g^? obtained for this meteorite compares well with a reported abundance of 19.3 μg g^?1 obtained by radiometric neutron-activation analysis (RNAA). The analysis of 15 meteorites that had previously been analysed by RNAA gave values averaging 11% below those reported by the latter method, but within the standard deviation of the RNAA data. It is considered that the present method is a more practical alternative to RNAA for the determination of ruthenium in iron meteorites.     

Using pulse shape discrimination to sort individual energy deposition events in a germanium crystal

A fast digital oscilloscope based pulse shape discrimination (PSD) system has been tested with intrinsic germanium detectors large enough to allow ionizing events which generate localized electron-hole pairs at a single site to be segregated from those depositing energy at several different sites in the crystal. Drift velocities of the electrons and holes result in pulses several hundred nanoseconds long. Since the electric field varies by almost a factor of 10 between the outer and inner surfaces, collection of electrons and holes can frequently be dinstinguished, and pulses due to multi-site events can be distinguished from single site events.