title: Preferential axial protonation in a zwitterionic calix[4]arene.
abstract: [structure: see text] Calixarene 3, substituted at two methylene bridges by dimethylamino groups, exists in the crystal and in polar solvents as a zwitterion, with the axial dimethylamino group protonated.
authors.affiliation: Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Samah
authors.initials: S
authors.lastname: Simaan
authors.forename: Silvio E
authors.initials: SE
authors.lastname: Biali