Vapour—liquid equilibrium of the systems 1-propanol—2,2,4-trimethylpentane and 2-propanol-n-hexane

The vapour—liquid equilibrium data were measured for the binary systems 2-propanol—n-hexane at 328.21 K and 1-propanol—2,2,4-trimethylpentane at 328.37 K and 348.52 K by using the recirculation still proposed by Berro et al. (1975). The excess volumes for these systems were measured with an Anton Paar densimeter. The reduction of VLE data and analysis of experimental errors were performed. The NRTL temperature-dependence parameters were estimated. The measured VLE data and the activity coefficients were compared with the values predicted by the chemical-reticular group-contribution method (CRG) (Neau and Péneloux, 1979). For both systems satisfactory agreement was found. This proves that the CRG model can be used to predict the vapour—liquid equilibria of alcohol—alkane systems containing branched components.     

A new ebulliometric technique. Vapour-liquid equilibria in the binary systems ethanol-n-heptane and ethanol-n-nonane

Berro, C., Rogalski, M. and Péneloux, A., 1982. A new ebulliometric technique. Vapour-liquid equilibria in the binary systems ethanol-n-heptane and ethanol-n-nonane. Fluid Phase Equilibria, 8: 55–73.This paper considers a modification to a recirculation still described previously by Berro et al. (1975). The ebulliometric apparatus is coupled to a closed flow system allowing continuous densimetric analysis of liquid and vapour phase compositions.Vapour-liquid equilibria have been measured for two systems: ethanol-n-heptane, at 303.27 (T-P-x data only) and 343.17 K; and ethanol-n-nonane, at 343.21 K. The experimental data were reduced using the observed-deviation method (Neau and Péneloux, 1981). The results of the reduction are presented and discussed.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Anion radical [2 + 2] cycloaddition as a mechanistic probe: stoichiometry- and concentration-dependent partitioning of electron-transfer and alkylation pathways in the reaction of the Gilman reagent Me2CuLi.LiI with bis(enones)

Exposure of easily reduced aromatic bis(enones) 1a-1e to the methyl Gilman reagent Me(2)CuLi.LiI at 0 degrees C in tetrahydrofuran solvent provides the products of tandem conjugate addition-Michael cyclization, 2a-2e, along with the products of [2 + 2] cycloaddition, 3a-3e. Complete partitioning of the Gilman alkylation and [2 + 2] cycloaddition pathways may be achieved by adjusting the loading of the Gilman reagent, the rate of addition of the Gilman reagent, and the concentration of the reaction mixture. The Gilman alkylation manifold is favored by the rapid addition of excess Gilman reagent at higher substrate concentrations, while the [2 + 2] cycloaddition manifold is favored by slow addition of the same Gilman reagent at lower concentrations and loadings. Notably, [2 + 2] cycloaddition to form 3a-3e is catalytic in Gilman reagent. Kinetic data reveal that the ratio of 2a and 3a changes such that the cycloaddition pathway becomes dominant upon increased consumption of Gilman reagent. These data suggest a concentration-dependent speciation of the Gilman reagent and differential reactivity of the aggregates present at higher and lower concentrations. While the species present at higher concentration induce Gilman alkylation en route to products 2a-2e, the species present at lower concentration provide products of catalytic [2 + 2] cycloaddition, 3a-3e. Moreover, upon electrochemical reduction of the bis(enones) 1a-1e, or chemically induced single-electron transfer from arene anion radicals, the very same [2 + 2] cycloadducts 3a-3e are formed. The collective data suggest that [2 + 2] cycloadducts 3a-3e arising under Gilman conditions may be products of anion radical chain cyclobutanation that derive via electron transfer (ET) from the Me(2)CuLi.LiI aggregate(s) present at low concentration. These observations provide a link between the Gilman alkylation reaction and related ET chemistry and suggest these reaction paths are mechanistically distinct. This analysis is made possible by the recent observation that easily reduced bis(enones) are subject to intramolecular [2 + 2] cycloaddition upon cathodic reduction or chemically induced ET from arene anion radicals, and is herewith showcased as a novel method of testing for the intermediacy of enone anion radicals.     

The preparation,properties, crystal lattice and thermal decomposition reactions of cobalt malonate dihydrate

Cobalt malonate dihydrate crystallizes in the monoclinic system, the dimensions of the unit cell are reported. On heating, two molecules of water are lost at ～400 K to give the anhydrous salt which is amorphous to X-rays. At higher temperatures (520K) the initial stages of carboxylate decomposition obey the zero-order kinetic equation to 30% reaction. Thereafter, there is a marked diminution in rate of the vacuum reaction but kinetic behaviour is sensitive to the gases present; the influences of reaction products, of carbon monoxide and of oxygen have been investigated quantitatively. Form these observations we conclude that the decomposition of cobalt malonate proceeds by an autocatalytic mechanism, through the nucleation and growth of an ill-crystallized mixture of product phases. The rate of reactions at the reactant-product contact surface are controlled, to some extent, by available gaseous molecules which may participate in equilibria at the interface and at active surfaces of the residual phases.