Addition d'hydrazone aux oléfines en milieu acide: cycloaddition polaire cationique [3+ + 2]

The stereospecificity and the orientation observed for the addition reaction of acetaldehyde hydrazone with (E)- and (Z)-alkenes in acidic media are compatible with a concerted process of the polar [3⁺ + 2] cycloaddition type.     

Contribution of the triangle graphs to the neutron electric dipole moment

In the Kobayashi-Maskawa model we compute a new contribution to the neutron electric dipole moment induced byCP violating flavour-changing transitions of the typess→d+gluon+γ through heavy quark loops. This contribution, essentially given by the triangle anomaly graph, is by itself gauge invariant. We obtain from this mechanismD _n /e=3.10^?32 cm, one order of magnitude below our previous estimate from usual penguin diagram contributions.     

Fluororganische Synthesen V Darstellung und Abwandlung von Chlorfluorcyclopropanen - Ein gezielter Zugang zu Fluorallylalkoholen

Fluoroorganic Syntheses V. Preparation and Transformation of Chlorofluorocyclopropanes. – A Selective Approach to Fluoroallylic Alcohols Chlorofluorocarbene addition to unsaturated compounds is particularly convenient and efficient in a two-phase system. This method works satisfactorily even if the olefin carries base-sensitive substituents. The resultant chlorofluorocyclopropanes can be ring-opened by silver-salt assisted acetolysis affording 2-fluorallylacetates, which yield 2-fluorallylic alcohols upon saponification.     

The infrared spectra of fused 1,2,4-triazin-5-ones

The IR spectra of a number of fused 1,2,4-triazin-5-ones have been studied and the relevance of the results to triazinone tautomerism is discussed.     

Angular distributions in the dimuon hadronic production at 150 GeV/c

From π^- interactions at 150 GeV/c on a heavy target, we present the final analysis of the dimuon decay angular distribution in the mass interval 4.5–8.5 GeV/c². Results are presented and discussed in various reference frames and are also given in terms of the density matrix elements. Finally the possible contribution of higher-twist effects at largex ₁ is discussed; we find that our data are not compatible with higher twist contributions as proposed by the Berger and Brodsky Model.     

Etude de la reactivite de l'ion azoture vis á vis de cations heterocycliques-I: Inhibition de la formation d'azides covalents par un complexe pyrylium-azoture constituant un “cul de sac” reactionnel. mise en evidence expérimentale

The reactivity of azide anion with pyrylium and thiopyrylium substituted cations depends on the substitution of the heterocyclic cation. Only sterically hindered pyrylium or thiopyrylium cations lead to the formation of covalent azides. On the other hand, pyrylium or thiopyrylium cations which are not sterically hindered give a donor acceptor complex. The formation of this complex constitutes a dead-end reaction on the normal pathway to covalent azides. This apparently unusual behaviour cannot be rationalized with simple concepts such as charge density or frontier orbital coefficients.     

A FTIR study of PVDF irradiated by means of swift heavy ions

Poly(vinylidene difluoride) (PVDF) films were irradiated by means of heavy ions (in the electronic stopping-power range) and electrons. Both types of ionizing radiation induce in the polymer film ionizations and excitations, but swift heavy ions induce a huge density of excitations and ionizations along the ion path. Dose-range goes from 0.3 to 40 MGy. Irradiations were performed with Kr ions in the presence of helium, hydrogen, deuterium, and oxygen. Fourier transform infrared (FTIR) transmission measurements show differences in the nature of the created defects. Triple bonds are characteristic of the Kr ion irradiation. Double bonds, isolated and conjugated, exist for both kinds of radiation, but concentrations are higher with the Kr radiation. The presence of oxygen during irradiation produces oxidization defects. Typical bands of hydroxyls and carbonyls can be seen, respectively, in the 3800-3000 cm^?1 zone and ca. 1850–1730 cm^?1. The formation of conjugated double bonds is enhanced when the Kr irradiation is performed under an O₂ atmosphere. © 1994 John Wiley & Sons, Inc.