No abstract

SHORT COMMUNICATIONSWe have revealed unusual transformations in the series of accessible N-(1-aryl-2,2,2-trichloroethyl)arenesulfonamides [1, 2] by the action of secondary amines in dimethylformamide or dimethyl sulfoxide. These transformations are accompanied by rearrangement, and they result in formation of a mixture of products. The reaction of N-[2,2,2-trichloro-1-(4methylphenyl)ethyl]-4-chlorobenzenesulfonamide (I) with an equivalent amount of dipropylamine in the presence of excess sodium or potassium carbonate gave a mixture of compounds from which we isolated N-[2-chloro-1-dipropylamino-2-(4-methylphenyl)ethylidene]-4-chlorobenzenesulfonamide (II) and N-[1,2-bis(dipropylamino)-2-(4-methylphenyl)ethylidene]-4-chlorobenzenesulfonamide (III). When the reaction was performed in the presence of excess amine, no compound II was isolated. The reaction in DMSO, apart from compounds II and III, afforded N- [1,2-dioxo-2-(4-methylphenyl)ethyl]-4-chlorobenzenesulfonamide (IV). The yield of the latter decreases as the amount of dipropylamine increases.The structure of products II-IV was confirmed by the data of elemental analysis and NMR spectroscopy ( 1 H, 13 C, 13 C JMOD, 13 C RGGD, two-dimensional techniques). A probable reaction mechanism leading to amidines II and III includes intermediate formation of 2,2-dichloro-1-(4-chlorophenylsulfonyl)-3-(4-methylphenyl)aziridine and its subsequent transformations by the action of secondary amine. Compound IV could be formed via hydrolysis of the aziridine intermediate, followed by oxidation of the hydrolysis product with DMSO.Study of the discovered transformations is now in progress with a view to elucidate their mechanism and develop effective methods for the preparation of new polyfunctional sulfonamide derivatives. Reaction of N-[2,2,2-trichloro-1-(4-methylphenyl)ethyl]-4-chlorobenzenesulfonamide (I) with dipropylamine.A mixture of 4.13 g (0.01 mol) of amide I, 2.12 g (0.02 mol) of sodium carbonate, 1.37 ml (0.01 mol) of dipropylamine, and 25 ml of DMSO was stirred for 1.5 h at 90°C. The mixture was

No abstract

No abstract

The existence of stable thermal stratification in a reservoir during the summer alters appreciably the conditions under which its oxygen regime is formed, since the thermocline prevents diffusion of oxygen supplied to the body from the atmosphere and during photosynthesis of algae, and from the epilimnion to the hypolimnion. As a result, water supersaturated with oxygen may be observed in the epilimnion, and, conversely, an oxygen deficit in the hypolimnion. In the near-bottom layers, its content may be diminished virtually to zero with fatal consequences for near-bottom and bottom fauna.The thermal regime of a stratified reservoir can be schematized by a two-layer model consisting of an epilimnion and hypolimnion, which separates the plane with a pronounced change (jump) in water temperature, being conditionally adopted as the thermocline. Here, the temperature of the upper boundary of the thermocline can be assumed equal to or less than the temperature of the water surface, and the temperature of the lower boundary equal to or greater than the temperature of the water at the bottom, depending on specific conditions. In the latter case, the temperature variation of the water throughout the depth of the epilimnion and hypolimnion is assumed to be linear. A similar assumption is also made for the variation in the oxygen content over the depth of the hypolimnion, which, as a rule, decreases with depth in mesotrophic and eutrophic bodies of water. As for the epilimnion in which, in contrast to the hypolimnion, the oxygen content is largely determined not by diffusion, but by adequate transfer, i.e., by the mixing of water (runoff, wind-generated, and convective flows), its oxygen content may be assumed constant over the depth. A mathematical model [1] on which the hypothesis of the ideal mixing of water in a reservoir on the whole, or taken layer at a time, is based, can then be used to calculate the oxygen regime of a stratified reservoir. Using this model, the oxygen regime is calculated successively in the epilimnion at first, and then in the hypolimnion. In that case, the thermal regime of some layers is assumed to be known, and the average velocities of the flows in these layers are assumed to be directly proportional to their average water temperature [2]. Proceeding from this condition, which is valid for poor circulating and deep reservoirs, irrespective of the degree of circulation in the latter (for which temperature stratification in the summer is also characteristic) and the draw down of water into the tailrace is known, the flow of water is determined separately for the epilimnion and hypolimnion, which will also determine the water volume in these layers, and, accordingly, their oxygen regime.The fact that the oxygen-saturation concentration of water O~ in both layers is determined by the surface temperature of the water is common to calculation of the regime in the epilimnion and hypolimnion. This temperature controls the equilibrium concentration of O 3 in the epilimnion. Maximum oxygen concentration...