Organic synthesis with sulphones—XVII: The anti-markownikoff halosulphonylation of olefins via an ionic pathway,and a new method of preparing benzenesulphonyl iodide

Iodine and bromine in the presence of sodium benzenesulphinate react with olefins in acetone solution to give halosulphones resulting from an apparent steric direction of attack at the intermediate halonium ion. A straightforward preparation of benzenesulphonyl iodide from benzenesulphonyl chloride and sodium iodide is also described.     

Developments on carbon dioxide reduction: Their promise,achievements, and challenges

CO₂ reduction processes continue to be developed for electrosynthesis, energy storage applications, and environmental remediation. A number of promising materials have shown high activity and selectivity to target reduction products. However, the progress has been mainly at a small laboratory scale, and the technical challenges of large scale CO₂ reduction have not been considered adequately. This review covers recent advancements in catalyst materials and cell designs. The leading materials for CO₂ reduction to a number of useful products are presented with their corresponding cell and reactor designs. The latest efforts to progress to industrially relevant scales are discussed, along with the challenges that must be met for carbon dioxide reduction to be a viable route for mass scale production.     

Topological degree of a family of convex functions and localization of nash equilibrium points

We define the degree of a family of convex functionsf _x, wherex , and prove that, if this degree is different from zero, one has at least one Nash equilibrium point in . This is a criterion of localization of such equilibrium points.     

Mechanism of formation and decay of the compound nuclei150Gd produced by two entrance channels (16O+134Ba) and (40Ar+110Pd)

Excitation functions have been drawn for evaporation residues issued from¹⁵⁰Gd, a compound nucleus produced either by¹⁶O ions on¹³⁴Ba, or by⁴⁰Ar on¹¹⁰Pd. Absolute cross sections were measured for^145–147Gd,^145–147Eu,^141m Sm,^143m Sm,^140m Pm and^139m Nd. Complete fusion cross sections have been obtained and compared to calculated estimations based, at low energies, on the simple expressionσ _CF=πR _Fuss ² (1?V _Fus/E) whereR _Fus andV _Fus are respectively the distance and the potential for fusion atdV/dr=0. For high energies σ_CF=πR _cr ² (1?V_cr/E) with the model of critical distanceR _cr and critical potentialV _cr. Thresholds energies have been determined with a particular care. The analysis of the shape and the width of excitation functions, particularly for the emission of 4 and 5 neutrons, has been carried out and compared to calculated values. The difference between argon and oxygen induced reactions has been attributed to the difference inl population in the entrance channel.     

Evaluation of Ptitsyn-Eizner λ parameter in dilute solutions of poly(N-vinylcarbazole) and its variation in conformational transitions of poly(methyl methacrylate)

The Ptitsyn-Eizner λ flexibility parameter for poly(N-vinylcarbozole) solutions under theta conditions has been found to be 6.31, demonstrating the rigidity imparted to the polymer chain by the carbazole group. A study has been made of the variation of this parameter with solvent and temperature. A study has been made of the variation of λ in a conformational transition of poly(methyl methacrylate).     

Chiral conformations induced by cyclodextrin

Studies of chiroptical properties need separation or at least enrichment of enantiomers. The separation is difficult with chiral conformers of molecules with very low barriers of internal rotation. However, in association with cyclodextrin, these labile molecules can exhibit a strong Cotton effect in solution: one chiral conformer is favoured by complexation. The cyclodextrins have the advantage to yield inclusion complex in solution as well as crystalline clathrates. Therefore, the absolute configuration of the guest can be obtained by determining the structure of the cyclodextrin. In this work, the first CD spectrum of 4-helicene is recorded and crystal structures of several clathrates of labile molecules are studied.     

Characteristics of immunosorbents used as a new approach to selective solid-phase extraction in environmental analysis

Summary The trace-level determination of organic pollutants in complex matrices is difficult and often not reliable because theccurrent extraction procedures are non-selective. New extraction sorbents involving antigen-antibody interactions, called immunosorbents (ISs), have been synthesised in order to trap a group of structurally related pollutants. The IS capacity is always high for the analyte-antigen used to make the antibodies, but can be low for some related compounds. In this work, we show the relationship that exists between capacity, break-through volume and recovery of analytes because of the competition between the structurally related compounds for antibody sites. Breakthrough due to the overloading of the column should be avoided because calibration curves are no longer linear. The capacity of two ISs, one made for trapping the triazine pesticide group and the second for the phenylurea, group, have been optimised by selecting silica with 50 nm pore size. Calibration curves are linear for all the compounds in a mixture of ten phenylureas up to a concentration of 5 to 10 μg L⁻¹ for each compound when handling 50 mL water samples through a precolumn packed with 0.22 g of IS. Under these conditions, reliable quantitative results are obtained because calibration curves are similar when compounds are alone or in a mixture. Application to the clean-up of soil extracts illustrates the high selectivity and the high potential of these new sorbents in environmental analysis. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Gould-Jacobs reaction of 6-amino-2,3-diphenylquinoxaline

Summary Catalytic hydrogenation of 2,3-diphenyl-6-nitroquinoxaline led to the corresponding amine1 which in turn afforded products3a-i on reaction with alkoxymethylene derivatives2a-i. Thermal cyclization of3b and3f yielded substituted pyrazinoquinolones5b and5f, respectively. Optimal conditions for the successful hydrolysis of ester5b were found. The structures of all products were deduced from their IR, UV,¹H, and¹³C NMR spectroscopic data.Dedicated to Prof.F. Sauter on the occasion of his 65th birthday     

Méthylène-indolines,indolénines et indoléniniums—XIII: L'hydroxy-16 déhydro-1 vincadifformine,intérmédiaire dans le réarrangement biomimétique de la vincadifformine en vincamine

The title compound is a crucial intermediate in the biomimetic conversion of vincadifformine 1 into vincamine 7. Its configuration at C-16 is established by a combination of chemical and spectroscopic evidence. Iodine oxidation converts 14 into the bridged lactam 18, thus proving a β configuration for the hydroxy group at C-16. The same reaction applied to vindoline 19 gives 21 identical with one of the compounds obtained by microbiological transformation of 19. The ¹³C NMR spectra of derivatives 3 and 8 (obtained by oxidation of vincadifformine) show that oxidation proceeds with introduction of the substituent at C-16, with a β-configuration. The alcohol 3 however, posesses a different conformation due to strong hydrogen bonding with N-4.