Exploiting Synergistic Effects in Organozinc Chemistry for Direct Stereoselective C‐Glycosylation Reactions at Room Temperature

Pairing a range of bis(aryl) zinc reagents ZnAr₂ with the stronger Lewis acidic [(ZnAr^F₂)] (Ar^F=C₆F₅), enables highly stereoselective cross‐coupling between glycosyl bromides and ZnAr₂ without the use of a transition metal. Reactions occur at room temperature with excellent levels of stereoselectivity, where ZnAr^F₂ acts as a non‐coupling partner although its presence is crucial for the execution of the C(sp²)–C(sp³) bond formation process. Mechanistic studies have uncovered a unique synergistic partnership between the two zinc reagents, which circumvents the need for transition‐metal catalysis or forcing reaction conditions. Key to the success of the coupling is the avoidance of solvents that act as Lewis bases versus diarylzinc compounds (e.g. THF).     

Vaporization energy change and vibrational frequency shift in substituted mono-halo-benzenes

Direct linear relation exists between the reduced vaporization energy change (H _v /RT _B ) of benzene and its homologues, C₆H₅X (X=F, Cl, Br, I) and the X-sensitive dimensionless frequency (hcv/kT _B ) at their respective normal boiling point (T _B ) temperatures.The financial assistance of the National Research Council of Canada, the Graduate Fellowship (J.B.B.), the University of British Columbia, and the NRC Bursaries (H.C.H., R.G.O.) are gratefully acknowledged.     

Rapid,quantitative analysis of americium,curium and plutonium isotopes in Hanford samples using extraction chromatography and precipitation plating

Recently developed methods for the rapid, quantitative analysis of americium (Am), curium (Cm), and plutonium (Pu) isotopes in Hanford soil, sludge, and waste-tank samples are described. After dissolution, dilutions are made as necessary based on alpha-energy analysis of a small aliquot of the original solution. Isotopic tracers are then added and Am-Cm and Pu are separated by extraction chromatography, coprecipitated with neodymium fluoride, and counted. Examples of alpha spectra are given, and results obtained for Hanford sludge samples are presented.     

Liquid-liquid extraction of transition and alkali metal cations by a new calixarene: Diphenylphosphino calix[4]arene methyl ether

The liquid-liquid extraction of various metal ions by a diphenylphosphino calix[4]arene (1) using picrate counter ion has been studied and compared with those ofp-tert-butyl-calix[4]arene methyl ether (2) and triphenylphosphine (3). The calixarene 1 shows strong binding ability to almost all metal cations examined, but calixarene 2 shows little ability to extract any of them. Based on the continuous variation method, calixarene 1 formed 1: 2 complexes with copper(II) ion.     

Spectrometric analysis of non-metals introduced from a graphite furnace into a microwave-induced plasma

A low-power helium microwave-induced plasma, sustained in a cylindrical TM(010) cavity, has been used with sample introduction from a graphite furnace. An end-on optical configuration was employed to monitor both atomic and ionic emission from Cl, I, S and P. The operating parameters were optimized with respect to the nature of the plasma background response, the limits of detection, and the shapes and linearity ranges of the log-log analytical working curves. Possible applications were evaluated by determining iodine in milk and analysing a multi-component mixture of sulphur compounds.     

PHOTOREACTIVITY OF 5-GERANOXYPSORALEN AND LACK OF PHOTOREACTION WITH DNA

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.