Most equimolecular mixtures of enantiomers, i.e., tively few (there are ca. 250 inventoried cases1) are conracemates, crystallize as racemic compounds, while reíaglomerates, i.e., cases which permit spontaneous resolution.

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Oil/water emulsions can be produced through phase inversion, by adding water to a reverse water/oil microemulsion. According to small angle neutron scattering experiments and visual observations performed during phase inversion, the stages of this process are as follows: (i) upon water addition, the microemulsion gives way to a highly swollen lamellar phase; (ii) the transient lamellar phase breaks up to yield an array of droplets; (iii) the droplets loses the correlations of the lamellar phase. This emulsion is already present less than one minute after the initial addition of water, and it reaches the final size distribution in one hour. The final population of oil droplets is homogenous with a mean diameter below 100 nm.

Abstract-The low temperature phase structure of the nitroxide radical 2,2,6,6-tetramethyl piperidin-1-oxyl (Tanane) is isomorphic of 2,2,6,6-tetramethyl-4-piperidinol-l-oxyl (Tanol). An ESR study of single crystals yielded the principal values and positions of principal axes of the g tensor in these two radicals. The major significant differences observed in Tanol are a moderate decrease in the g,,, g,, and g,, values, and a deviation of the principal axes situated in the molecular mirror plane (2,;) from the N-0 bond and r-orbital, respectively (So f 2"). The intermolecular hydrogen bond is probably responsible for this fact.Rksum6-La structure de la phase basse temperature du radical nitroxyde tBtramBthyl-2,2,6,6 pip6ridine oxyle-1 (Tanane) a Bt6 dCterminCe. Ce radical libre est isomorphe du t&ramethyl-2,2.6,6 pip6ridinol-4 oxyle-1 (Tanol). Une Btude en resonance paramagn6tique Clectronique de monocristaux a permis de determiner les valeurs principales et I'orientation des axes propres du tenseur g pour ces deux radicaux. Pour le Tanane, la liaison N-0 est une direction propre du tenseur 2. Pour le Tanol, il existe un angle de 8" i 2" entre cette direction propre et la liaison N-0. I1 est vraisemblable que, dans le cas du Tanol, la liaison hydroghe intermolkculaire est responsable de la deviation observee pour les axes propres situes dans le plan miroir (2, C), ainsi que des plus faibles valeurs mesurkes pour g,,, g,, et gsz.