Piperazin-1-ium 4-aminobenzoate monohydrate

The asymmetric unit of the title hydrated salt, C4H11N2+·C7H6NO2−·H2O, contains a piperazin-1-ium cation, a 4-aminobenzoate anion and a water molecule. One NH group of the piperazine ring is protonated and this ring adopts a chair conformation. The anion of this salt is generated by deprotonation of the OH group of the carboxylic acid substituent of 4-aminobenzoic acid. The benzene ring makes a dihedral angle of 2.6 (2)° with the carboxylate substituent. The anion and the solvent water molecule are linked by an N—H...O hydrogen bond. Additional N—H...O and O—H...O hydrogen bonds connect adjacent anions through the water molecules, generating a two-dimensional network parallel to (100), forming R33(12) ring motifs. Adjacent cations are linked by N—H...N hydrogen bonds into infinite chains along (001). These chains are linked to the two-dimensional network of anions and water molecules by another N—H...O hydrogen bond, forming a three-dimensional network