A Mössbauer and Electrochemical Characterization of the Corrosion Products Formed from Marine and Marine-Antartic Environments

Hyperfine Interactions - Corrosion products formed on low alloy steel under two marine environments are characterised. Both environments are classified as C4 according to the ISO 9223 Standard. The...     

Stereochemistry of grignard reactions on some conformationally mobile δ-keto esters: The effects of changing solvent and reactant

Methyl 4-methyl-5-oxo-hexanoate (4) and methyl 4-methyl-5-oxo-5-phenyl-pentanoate (5) yield mixtures of cis and trans tetrahydro-5, 6-dimethyl-6-phenyl-2H-pyran-2-one (6+7) on reacting with PhMgX and MeMgX, respectively. Ratios $\text{6}\text{7}$ were measured for reactions performed in benzene, diethyl ether (with XI) and tetrahydrofuran (with XCI). A comparison is made of the results obtained with those of methyl (2-oxo-cyclohexyl)-propionate (1). It is suggested that the ester group and the keto group can interact in the transition states of the reaction performed in the less polar solvent and that in polar solvents they are remote from one another during the reaction. These conformational changes are believed to be responsible for the observed stereochemical differences in the reactions.     

From crystal to micelle: A new approach to the micellar structure

The structure of sodium and rubidium deoxycholate micellar aggregates in aqueous solutions was found to be helical and to be stabilized mainly by polar interactions. Astonishingly, the lateral surface of the helix is covered by nonpolar groups and the interior part is filled with cations surrounded by water molecules, as in the case of an inverted micelle. This helical model was inferred from the crystal structures of sodium and rubidium deoxycholates and proved by spectroscopic and diffractometric experimental data. The strategy of the approach to the determination of the micellar structure and the comparison with another model, previously proposed for the bile salt micelles, are reported. On the basis of some results obtained for sodium tauro- and glyco-deoxycholates, micellar models are suggested which could account for the biological function of these important conjugated bile salts.