Synthèse et propriétés acido-basiques de l'acide calix[6] arène hexasulfonique hydraté

The hydrated hexasulfonic calix[6]arenes of formulae (C 7 H 6 O 4 S) 6 7H 2 O1 and (C 7 H 6 O 4 S) 6 16H 2 O2 have been synthesized and characterized. Compound 1 is hydroscopic, rapidly giving rise to compound 2 when left in contact with air. When heated, it remains stable until approximately 100°C; thereafter it loses seven water molecules and decomposes around 270°C. The acid-base behaviour of these potential ligands H 12 A shows that in aqueous solution, two of the six OH groups dissociate between pH 2.5 and 7(pK 6 H =3.45; pK 5 H =5.02) whereas the four remaining OH groups only dissociate at pH>11