SummaryThe synthesis of a series of polyguanidinium salts of potential interest as anion complexones is described. Among the various synthetic methods investigated, the polyguanidinium salts were found to be most conveniently prepared from polyamines via polypitroguanidine intermediates. The complexation of phosphate and carboxylate anions by these complexones and by related polyammonium salts were studied by analysis of pH-metric titration data. The ligands studied form relatively stable complexes (log K,= 2.0-4.0 for PO:-in water) which also present good selectivities in some cases. Both the stability and the selectivity of complexation are primarily governed by electrostatic forces and thus depend on charge accumulation in the interacting species; structural effects are also observed. Since the binding is primarily electrostatic, polyammonium salts form more stable complexes (at a given charge) than do polyguanidinium salts. However, whereas the complexation properties of the latter are independent of pH, the complexes of the former are observed only in the limited ranges of pH where both the protonated polyamine and the anion of interest can coexist. The polycationic ligands may, in principle, form chelate type anion complexes. Comparison with the corresponding single binding sites reveals an increase in complexation constant of about two or three orders of magnitude; this may be considered as a thermodynamic indication of a chelate effect for the polydentate ligands (by analogy with the well known effects displayed by cation complexones); however, structural data on the formation of chelate 'rings' are not yet available. The nature of the complexes and the prospects of anion complexones in various fields are discussed.

No abstract

Low-temperature nitration of the title compounds in acetic anhydride gives 1,2 nitronium acetate adducts, except p-fluorotoluene which gives both 1,2 and 1,4 adducts and a-p-tolyloxyisobutyric acid which gives a spiro adduct.NITRATION of appropriately substituted aromatic compounds in acetic anhydride leads to the formation of nitronium acetate a d d ~c t s . l -~ The reaction is initiated by the addition of nitronium ion to an ips0 position. The great majority of substrates investigated have given 1,4 adducts. However, P-t-butyltoluene* and 2-nitro-p-xylene5 each

Nitration of 4-acetamido-, 4-chloro-, and 4-methoxy-toluene in acetic anhydride gives in each case a cis 1,2 nitronium acetate adduct in addition to the nitro substitution product(s). Nitration of 4-fluorotoluene gives a pair of diastereomeric 1,4 nitronium acetate adducts and the cis 1,2 adduct.

Die bequemste Art, die Titelverbindungen (IV)‐(VI) darzustellen, ist die Umsetzung z.B. des Diamins (I) in Wasser bei 5°C mit dem Nitroisoharnstoff (II) zum Derivat (III), dessen Hydrogenolyse in saurer Lösung zum Ethylendiguanidinium (IV) führt.