Ethyl-4,4,4-trifluoroacetoacetate (ETFAA), a powerful building block for enantiopure chirons in trifluoromethyl-β-amino acid series

Herein are studied new transformations of ethyl-4,4,4-trifluoroacetoacetate (ETFAA), giving access to a series of enantiopure chirons bearing both a trifluoromethyl group and an amino moiety. The key intermediate is obtained optically pure by a resolution procedure.     

Observation of laser driven supercritical radiative shock precursors

We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations.     

1,4-dioxene in organic synthesis: rapid access to the oxabicyclo

[formula: see text] Oxidation of 2,3-disubstituted 1,4-dioxenes 3 with m-chloroperbenzoic acid in methanol followed by nucleophilic addition of allyltrimethylsilane in the presence of TiCl4 afforded dienes 5, which have been converted to oxabicyclo[4.2.1] nonenes 8 in excellent yield by olefin ring-closing metathesis reaction.     

Essai de mesure de l'epaisseur des couches d'oxydes par irradiation aux neutrons de 14 MeV

It is shown that the superficial oxygen content of thin aluminium foils can be found using 14 MeV neutron activation. The results obtained with this method are in good agreement with those given by ellipsometric methods for oxide layers from 50 to 500 Å.     

POLAR project: Numerical modeling of the accretion column

In this paper we study the formation and evolution of radiative accretion shocks in the context of accretion columns in magnetic cataclysmic variables. The phenomenon induces extreme regimes of matter and the radiation emitted by those region dominates the observed emission from polars. A 2D hydrodynamical code, HYDRO-COOL, has been developed in order to deal with high-Mach number flows and is currently improved to produce a numerical model of the accretion column. This code is the hydrodynamical part of the HADES code which aims at modeling radiative hydrodynamical systems. The final goal of this model is to improve our understanding of observational results. First numerical results are reported here, as well as a discussion about the time-dependent evolution of the column.     

Long-lived 1-adamantaneimminyl free radical as studied by ESR in 1-cyanoadamantane

The products of γ-irradiation of 1-cyanoadamantane were studied as a function of temperature by ESR spectroscopy. 1-adamantyl, 1-cyanoadamantyl and 1-adamantaneimminyl free radicals are formed in proportions depending on temperature. The low-temperature major product, 1-cyanoadamantyl transforms upon heating into the imminyl free radical which can be used as a spin label for studying molecular dynamics in glassy crystalline 1-cyanoadamantane.     

Temperature and Pressure Dependence Studies of the Motions of the +NH3 Radical Trapped in γ Irradiated Ammonium Perchlorate Single Crystal

The temperature and pressure dependences of the ⁺NH₃ coupling tensors have been investigated by ESR spectroscopy. The linear variation of the reduced correlation time of the “rotational diffusion” motion with reciprocal of the temperature is shown to be unrelated to the dilatation of the matrix. Comparison with ⁺ND₃ results gives the contribution to the nitrogen isotropic coupling constant of the out of plane vibration of the nitrogen atom.