On the PdCl2-catalyzed synthesis of allylic azides and allylic sulfonamides from homoallylic alcohols

According to experimental and literature data, the one-pot formation of allylic azides or sulfonamides from catalytic amounts of PdCl₂, homoallylic alcohols and TMSN₃ or TsNH₂ occurs through CC migration followed by regioselective nucleophilic addition on the Pd^II-activated CC bond and β-OH elimination.     

Length and density changes of amorphous Pd40Cu30Ni10P20 alloys due to structural relaxation

The density changes of bulk amorphous Pd₄₀Cu₃₀Ni₁₀P₂₀ due to structural relaxation under isothermal heat treatment were measured using the buoyancy method. The corresponding length changes of amorphous Pd₄₀Cu₃₀Ni₁₀P₂₀ ribbons applying non-isothermal heat treatment are determined applying dilatometry. The measured density changes Δρ(T=const.,t)/ρ_o as a function of isothermal heat treatment increase close to the glass transition up to 0.18%. The measured density changes as a function of temperature and time are furthermore reversible. The experimental data validate the model predictions of the free volume model for length and density changes of amorphous alloys due to structural relaxation applying isothermal and non-isothermal heat treatment.     

Lattice systems with a continuous symmetry

We prove that the expansion in powers of the temperatureT of the correlation functions and the free energy of the plane rotator model on ad-dimensional lattice is asymptotic to all orders inT. The leading term in the expansion is the spin wave approximation and the higher powers are obtained by the usual perturbation series. We also prove the inverse power decay of the pair correlation at low temperatures ford=3.Supported by NSF Grant No. MCS 78-01885Supported by NSF Grant No. PHY 78-15920Supported by NSF Grant No. DMR 73-04355Supported by NSF Grant No. PHY-7825390 A01On leave from: Institut de Physique Théorique, Université de Louvain, BelgiumAlso: Department of Physics     

Filiation structurale des phases de´rive´es de BaFeF5

Au sein d'un re´seau de type BaFeF₅ des chai?nes d'octae`dres fluore´sa`sommets communs peuvent disparai?tre en donnant naissance a des canaux dont l'occupation partielle ou totale par des files de cations Sr²⁺ et de couples d'anions F^?, conduit respectivement aux phases Sr₃(FeF₆)₂ ou Sr₅T₃F₁₉ (T = Cr, Co, Ga). Une discussion cristallochimique permet d'expliquer l'existence d'un domaine de solutions solides au sein du diagramme ternaire SrF₂BaF₂FeF₃.     

Monte Carlo simulations of chains confined inside a cube

Self-avoiding walks (SAWs) and random-flight walks (RFWs) of various lengths embedded on a simple cubic lattice have been computer generated inside cubes of varying side. If B is the side of the confining cube, we define the reduced cube side size B₀ as B₀ = (B − 1)/<r²>^1/2, where <r²>^1/2 is the root-mean-square end-to-end distance of the non-confined chains. Dimensionless diagrams are then given of the Monte Carlo estimates for the dimensions, the entropy, and the compressibility parameter PV/(kT) of the confined chains as a function of B₀. The comparative behaviour of the confined SAWs and RFWs is established, scaling properties are examined, and the Monte Carlo estimates compared with theory when such theory is available.     

Removal of diphenhydramine from water by swelling clay minerals

Frequent detection of pharmaceuticals in surface water and wastewater attracted renewed attention on studying interactions between pharmaceuticals and sludge or biosolids generated from wastewater treatment. Less attention was focused on studying interactions between pharmaceuticals and clay minerals, important soil and sediment components. This research targeted on investigating interactions between diphenhydramine (DPH), an important antihistamine drug, and a montmorillonite, a swelling clay, in aqueous solution. Stoichiometric desorption of exchangeable cations accompanying DPH adsorption confirmed that cation exchange was the most important mechanism of DPH uptake by the swelling clay. When the solution pH was below the pK(a) of DPH, its adsorption on the swelling clay was less affected by pH. Increasing solution pH above the pK(a) value resulted in a decrease in DPH adsorption by the clay. An increase in d(001) spacing at a high DPH loading level suggested interlayer adsorption, thus, intercalation of DPH. The results from this study showed that swelling clays are a good environmental sink for weak acidic drugs like DPH. In addition, the large cation exchange capacity and surface area make the clay a good candidate to remove cationic pharmaceuticals from the effluent of wastewater treatment facilities.     

Phase Change in a Heterogeneous Medium: Comparison Between the Vaporisation of Water and Heptane in an Unsaturated Soil at Two Temperatures

A theoretical and experimental analysis of the phase change of a volatile liquid in an unsaturated soil is presented. Expression of the rate of phase change of the pore liquid is developed within the framework of nonequilibrium thermodynamics. An experiment is proposed in which the value of the phenomenological coefficient associated with this expression is measured. Two examples of results concerning the volatilisation of water and of a volatile hydrocarbon in a silty clayey sand illustrate the potentiality of the experiment. Variation of the phase change coefficient was determined at 30°C for both fluids and at 80°C for heptane, versus the liquid content of the soil.