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Selenium Diimides, Aminoselenanes, l5N N M R , 77Se N M R , Coupling C onstants / ( 77Se15N) Selenium diimides R(NSeN)R [R = 'Bu (la ), 'Oct (1 b)], the eight-membered heterocycle 'BuN(SeSeSe)2N'Bu (2) and the aminoselenanes of the type [R(Cl3Si)N]2Se (4a,b) and [(Me3Si)2N]2Se (5) were studied by multinuclear N M R with emphasis on l5N N M R for detec tion of coupling constants J(77Se15N). The selenium diimides possess the largest values of '/ ( 77Sel5N) observed so far ( la : 158.4 and 163.5 Hz; lb : 158.6 and 162.8 Hz). Com pound lb was found to be much more stable than 1 a, the heterocycle 2 being the m ajor decomposition product of la . The selenium diimides ( la ,b ) react readily with hexachlorodisilane to give the bis[alkyl(trichlorosilyl)amino]selenanes 4a,b. The solid state 13C, 15N, 29Si and 77Se CP/M AS N M R spectra of bis[bis(trimethylsilyl)amino]selenane (5) gave results in accord with the known crystal structure, and there is agreement with the solution state N M R data.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are widely distributed in the environment. In this study the accumulation potential of PFOA and PFOS in two fish species with different feeding strategies, i.e. chub (Leuciscus cephalus) and river goby (Gobio gobio) inhabiting a river receiving treated waste waters from a municipal waste water treatment plant, were estimated. PFOS was detected in chub (7-250 microg kg(-1) wet weight) and river goby (70-400 microg kg(-1) wet weight) with bioaccumulation factors (BAFs) of 4600 (liver) and 11,000 (organs). PFOA concentrations in both fish were low and in chub mostly below detection limit.

Environmental ranking of refrigerants is of need in many instances. The aim is to assess the relative environmental hazard posed by 40 refrigerants, including those used in the past, those presently used, and some proposed substitutes. Ranking is based upon ozone depletion potential, global warming potential, and atmospheric lifetime and is achieved by applying the Hasse diagram technique, a mathematical method that allows us to assess order relationships of chemicals. The refrigerants are divided into 13 classes, of which the chlorofluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, hydrofluoroethers, and hydrocarbons contain the largest number of single substances. The dominance degree, a method for measuring order relationships among classes, is discussed and applied to the 13 refrigerant classes. The results show that some hydrofluoroethers are as problematic as the hydrofluorocarbons. Hydrocarbons and ammonia are the least problematic refrigerants with respect to the three environmental properties.