Zwikker

An interesting alternative method for formulating f/(jt) was proposed in 1929 by de Boer and Zwikker [80], who suggested that the adsorption of nonpolar molecules be explained by assuming that the polar adsorbent surface induces dipoles in the first adsorbed layer and that these in turn induce dipoles in the next layer, and so on. As shown in Section VI-8, this approach leads to... 

ZSM-5 catalyst ZSM-5 zeolite Zudopenthixol [53772-Zvyagintsevite Zweifel alkene synthesis Zwikker reaction... 

Hydantoin itself can be detected ia small concentrations ia the presence of other NH-containing compounds by paper chromatography followed by detection with a mercury acetate—diphenylcarba2one spray reagent. A variety of analytical reactions has been developed for 5,5-disubstituted hydantoias, due to their medicinal iaterest. These reactions are best exemplified by reference to the assays used for 5,5-diphenylhydantoiQ (73—78), most of which are based on their cycHc ureide stmcture. Identity tests iaclude the foUowiag (/) the Zwikker reaction, consisting of the formation of a colored complex on treatment with cobalt(II) salts ia the presence of an amine (2) formation of colored copper complexes and (3) precipitation on addition of silver(I) species, due to formation of iasoluble salts at N. ... 

Por the formylation of amines with the mixed anhydride of formic and trimethylacetic acid, see Vlietstra, E.J. Zwikker, J.W. Nolte, R.J.M. Drenth, W. Reel. Trav. Chim. Pays-Bas, 1982, 101, 460. 

The ZwiKKER reaction involving Co + salts is frequently used for the detection barbituric acid derivatives [31-35], but some purine, pyridine and piperidine derivati and heterocyclic sulfonamides also yield colored derivatives. The Zwkker reaction particularly sensitive when it is possible to form a tetrahedral complex [Co(Barb) Xj] (X = donor ligand, e.g. amine) [4]. 

Zwikker A 1% cobaltous nitrate in absolute ethanol is sprayed on the plate, which is dried (at room temperature) and exposed to a wet chamber containing 25% ammonium hydroxide. 

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