synthesis and dissociation constants of calix(6)arene hydroxamic acids

calix(6)arene hydroxamic acids (iii) are synthesised for the first time by reactingcalix(6)arene acid chloride(ii) with substituted hydroxylamines at low temperature in the presence ofsodium bicarbonate. the p-carboxycalix(6)arene(i) is obtained by an acid catalysed condensationreaction of p-hydroxybenzoic acid and formaldehyde. these calixarenes are characterised by meltingpoint, uv, ir, 1h nmr and mass spectra. the thermodynamic ionization constants of calixarenehydroxamic acids have been determined by a ph titration technique in dioxane-water media.