4)xylylene (2) in solution, the paramagnetism of the blueviolet crystals indicates the presence of radicals (and possibly twisted biradicals (4)). By suitable substitution of the dibromide (f), it can be shown that the difference in behavior of the Thiele hydrocarbon ( 5 ) from that of thep-xylylene (2) is due to interaction of the mutual hindrance of the H atoms on C-1 and C-2' with the aromatization tendency of the quinonoid system.Thus the properties of the p-xylylene system (2) remain essentially unchanged by substitution at C-2 and 12-3, whereas radicals very sensitive to oxygen are obtained, e.g. ( 7 ) and ( 8 ) , when methyl groups are introduced in positions 1 or 2'.In hydrocarbon (61, on the other hand, the mutual hindrance of the H atoms in positions 1 and 2' is removed as a result of the angular structure. Hence compound (6), like the Thiele hydrocarbon (5), is stable as the p-xylylene and in contrast to (2) shows no tendency to oligomerize.Formation of complexes between cations of alkali metals or alkaline earth metals and organic ligands is of importance in:1. The activation of inorganic anions in organic solvents; 2. The transport of cations.We have synthesized diazapolyoxa macrobicyclic compounds of the following type"]:The substances react with a variety of cations to form stable complexes which may be regarded as inclusion compounds. Since the cation is "hidden" in the center of the molecule, the name "cryptates" is proposed for these compounds. The stabilityconstants of complexes of ( I ) with alkali metals and alkaline earth metals decrease in the following order:(in water). Both the bicyclic compounds and the complexes can occur in several conformations. Compound ( I ) can be used as a means for dissolving inorganic salts in organic solutions, e.g. KSCN, KF, and Ba(SCN)Z can be dissolved in chloroform.In a few cases the rate of cation exchange (in DzO) could be measured by N M R spectroscopy. At 30°C alkali metal cations exchange much more rapidly than alkaline earth metals.If potassium hydroxide is dissolved in tetrahydrofuran together with (f), the hydroxide ion becomes a very strong base which, among other things, cleaves a proton from the methylene group in fluorene.Radioactive drugs, e.g. compounds containing 1311 or 32P, are widely used in nuclear medicine as radiopharmaceuticals for localization of different organs and functional diagnosis. Moreover, the term "radioactive drugs" can also refer to drugs that are, in themselves, not radioactive but have been labeled with radioisotopes. Such labeled compounds are used in the elucidation of questions involving the resorption, distribution, and excretion, as well as for the study of the metabolism, of these drugs in the organism. The development and testing of new drugs by the pharmaceutical industry would nowadays be almost unthinkable without using radioisotopes. In contrast, these methods have found almost no application in pharmaceutical edocation at universities. Radioactive drugs can be synthesized by the standard methods of prepara...
