On almost periodic orbits and minimal sets

In this short note we solve in the negative the three problems recently posed by Jie-Hua Mai and Wei-Hua Sun regarding the behaviour of almost periodic orbits and minimal sets of dynamical systems whose phase space is not regular.     

Sulphur overlayers on the Au(1 1 0) surface: LEED and TPD study

The adsorption and desorption of sulphur on the clean reconstructed Au(1 1 0)-(1 × 2) surface has been studied by low energy electron diffraction, Auger electron spectroscopy and temperature programmed desorption. The results obtained show a complex behaviour of the S/Au(1 1 0) system during sulphur desorption at different temperatures. Two structures of the stable ordered sulphur overlayer on the Au(1 1 0) surface, p(4 × 2) and c(4 × 4), were found after annealing the S/Au(1 1 0) system at 630 K and 463 K, respectively. The corresponding sulphur coverage for these overlayers was estimated by AES signal intensity analysis of the Au NOO and S LMM Auger lines to be equal to 0.13 ML and 0.2 ML, respectively. Both sulphur structures appear after removing an excess of sulphur, which mainly desorbs at 358 K as determined from TPD spectra. Furthermore, it was not possible to produce the lower coverage p(4 × 2) sulphur structure by annealing the c(4 × 4) surface. In the case of the p(4 × 2) S overlayer on the Au(1 1 0)-(1 × 2) surface it is proposed that the sulphur is attached to “missing row” sites only. The c(4 × 4) S overlayer arises via desorption of S₂ molecules that are formed on the surface due to mobility of sulphur atoms after a prolonged anneal.     

Polar effects in free-radical reactions. A new type of homolytic aromatic alkylation by silver catalyzed oxidation of acetone by peroxydisulphate in the presence of olefins.

Silver catalyzed peroxydisulphate oxidation of acetone in the presence of olefins and protonated heteroaromatic bases leads to compound I via addition of acetonyl radical to the olefin and scavenging of the resulting radical adduct by the aromatic base.     

Total Syntheses and In Vivo Quantitation of Novel Neurofuran and Dihomo‐isofuran Derived from Docosahexaenoic Acid and Adrenic Acid

Neurofurans (NeuroFs) and dihomo‐isofurans (dihomo‐IsoFs) are produced in vivo by non‐enzymatic free‐radical pathways from docosahexaenoic and adrenic acids, respectively. As these metabolites are produced in minute amounts, their analyses in biological samples remain challenging. Syntheses of neurofuran and dihomo‐isofurans described are based on a pivotal strategy, thanks to an enantiomerically enriched intermediate, which allowed, for the first time, access to both families: the alkenyl and enediol. Owing to this formation, quantitation of specific NeuroF and dihomo‐IsoFs in biological samples was attainable.     

New examples of template catalysis based processes: glycerol-like units as efficient promoters for dehydrative nucleophilic substitutions of ferrocenylmethanol

The direct high-yield synthesis without solvent and catalyst, under mild conditions, of eleven novel mono substituted ferrocenylmethyl ethers and amine derivatives from ferrocenemethanol and vicinal oxygenated alcohols and amines is here reported. The peculiar ability of these classes of non acidic compounds to favor the dehydrative nucleophilic substitution is attributed to the presence of vicinal oxygen atoms to the reactive group able to build a hydrogen bonding network with the reactant. The role of carbon dioxide and hexafluoroisopropanol was investigated to support the hypothesis that a template catalysis effect is occurring. The in vitro anti-fungal activity of some of these derivatives was tested on two plant fungi, Botrytis cinerea and Penicillium species, with moderate activity.