18-CROWN-6 AND SMALL CARBOXYLIC-ACIDS - F ORMATION AND STRUCTURE OF BINARY ADDUCTS WITH FORMIC AND ACETIC-ACID, AS WELL AS TERNARY ONES WITH ACETIC-ACID AND WATER

The melting diagrams of the binary systems 18-crown-6/formic acid and 18-crown-6/acetic acid have been set up and the crystal structures of the adducts 18C6 . 2 HCOOH (1, space group P2(1)/c with Z = 2 formula units per unit cell) and 18C6 . 2 CH3COOH (2, C2/m, Z = 2) determined, Furthermore three ternary phases, 18C6 . CH3COOH . H2O (3, P2(1)/c, Z = 4) and dimorphic 18C6 . 2 CH3COOH . 4 H2O (high temperature form 4. P2(1)/n, Z = 2; low temperature form 5, P2(1)/n, 2 = 2) have been cha racterized in the same way. In each structure the crown ether molecule has the (pseudo) D-3d conformation common for many of its complexes. Various aspects of the intermolecular hydrogen bonding are described.