Kinetics of the reactions of the IO radical with dimethyl sulfide,methanethiol, ethylene,and propylene

The reactions of IO radicals with CH₃SCH₃, CH₃SH, C₂H₄, and C₃H₆ have been studied using the discharge flow method with direct detection of IO radicals by mass spectrometry. The absolute rate constants obtained at 298 K are the following: IO + CH₃SCH₃ → products (1): k₁ = (1.5 ± 0.2) × 10^?14; IO + CH₃SH → products (2): k₂ = (6.6 ± 1.3) × 10^?16; IO + C₂H₄ →products (3): k₃ < 2 × 10^?16; IO + C₃H₆ → products (4): k₄ < 2 × 10^?16 (units are cm³ molecule^?1 s^?1). CH₃S(O)CH₃ and HOI were found as products of reactions (1) and (2), respectively. The present lower value of k₁ compared to our previous determination is discussed.     

Template synthesis in the nickel(II)–thiocarbohydrazide–propanone triple system

The complexing process proceeding in the Ni^II–thiocarbohydrazide (H₂N–H–NC(=S)–NH–NH₂)–propanone triple system in EtOH solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix has been studied. It has been found that in the first case, template synthesis leading, as a minimum, to formation of three coordination compounds of Ni^II with (N,N,S,S)-donor tetradentate ligands having NiL¹, NiL² and NiL³compositions where L¹ is 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-di(thiohydrazide)-1,9, L² is 4,6,6,12-tetrametyl-1,9-dithio-2,3,7,8,10,11-hexaazatridekadien-3,11-hydrazide-1 and L³ is 2,8,10,10,16-pentamethyl-5,13-dithio-3,4,6,7,11,12,14,15-octaazaheptadekatrien-2,7,15 is observed, whereas in the gelatin-immobilized matrix, a complexing process in the system considered does not occur.     

Consequence of boar edible tissue consumption on urinary profiles of nandrolone metabolites. II. Identification and quantification of 19-norsteroids responsible for 19-norandrosterone and 19-noretiocholanolone excretion in human urine

In previous work (Le Bizec et al., Rapid Commun. Mass Spectrom. 2000; 14: 1058), it was demonstrated that a boar meal intake could lead to possible false accusations of abuse of 17beta-nortestosterone in antidoping control. The aim of the present study was to identify and quantify endogenous 19-norsteroids in boar edible tissue at concentrations that can alter the steroid urinary profile in humans, and lead to excretion of 19-norandrosterone (19-NA) and 19-noretiocholanolone (19-NE). The samples were analysed in two laboratories. The methodologies used for extraction and detection (GC/MS(EI) and LC/MS/MS(APCI+)) are compared and discussed. 19-Norandrostenedione (NAED), 17beta- and 17alpha-nortestosterone (bNT, aNT), and 17beta- and 17alpha-testosterone (bT, aT) were quantified. The largest concentrations of NAED and bNT were observed in testicles (83 and 172 microg/kg), liver (17 and 63 microg/kg) and kidney (45 and 38 microg/kg). A correlation between the bNT and NAED content of a typical meal prepared with boar parts and the excreted concentrations of 19-NA and 19-NE in human urine was demonstrated.     

The toxic effect of aluminium in vines

The split-root technique was used to study the effect of varying the growth media on the elemental content of nutrient elements in the roots of grape vines. The varieties 2-1 (R99 x Jacquez) and Sauvignon blanc (Vitis vinifera) were grown in Hoagland water culture with and without added aluminium. The elemental concentrations of Mg, Al, Si, P. S, Cl, K and Ca in the dried roots were determined by PIXE. Roots grown in Al-rich media were deficient in Mg and Ca, but enriched in Al. There was a correlation between Al and Si but the uptake differed in the two varieties.     

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.     

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.     

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.     

PHOTOVOLTAIC ACTION SPECTRA AND EFFICIENCIES OF CHLOROPHYLL a SPECIES ABSORBING NEAR 700 nm

Abstract— Alcohol vapors affect the photovoltaic properties of anhydrous chlorophyll a (Chi a). At 23°C, a photovoltaic cell of the type Allanhydrous Chi a|Ag has been successively submitted to non saturating vapors of methanol, ethanol, 1-propanol, 2-propanol, cyclopropyl carbinol, cyclopentanol, methyl cyclopropyl carbinol, 1-butanol, 1-pentanol and chloroethanol. The action spectrum of anhydrous Chi a has a maximum in the red at 672 nm. This maximum is shifted towards 700 nm under the influence of alcohol vapors. The most important changes occur for ethanol, 1-propanol and 2-propanol. In the same way, the conversion efficiencies of light energy into electrical energy, measured at the maximum in the red are, for the same alcohols, higher than the initial value 1.7 times 10^-2% obtained on the average for anhydrous Chi a. A maximum value of 6.3 times 10^-2% has been obtained after rehydration of Chi a solvated with 2-propanol. The influence of alcohol vapors has been interpreted in terms of microcapillarity of anhydrous Chi a and a mean microcavity radius of 11 ± 6 Å has been deduced from the photocurrent variation with the amount of alcohol vapor present in the measuring area. Furthermore, the action spectrum shift towards 700 nm has been interpreted by the formation, at 23°C, of Chi a special aggregates whose action spectrum has been obtained by difference. Infrared spectroscopy demonstrated that anhydrous Chi a obtained from electrodeposition is an assembly of Chi a dimers and that alcohol vapors, producing the special aggregates formation at 23°C, induce a decrease of the free C=O ketone band and an increase of the associated C=O ketone. The C=O esters band is not affected by the Chi a reorganization.