CRYSTAL-STRUCTURE OF 2-CARBOXY-N,N,N-TRIMETHYLETHANAMINIUM BROMIDE MONOHYDRATE

A new betaine derivative, 2-carboxy-N,N,N-trimethylethanaminium bromide monohydrate, (Me3NCH2CH2COOH)Br.H2O, I, has been synthesized and characterized by X-ray crystallography. Compound I crystallizes in space group Pnma (No. 62), with a = 10.452(2), b = 6.855(2), c = 13.737(2) angstrom, and Z = 4. The structure (R(F) = 0.047 for 881 observed (\F0\ > 6-sigma\F0\) Mo K-alpha data) features a hydrogen-bonded (Br-.H2O) infinity zigzag chain running parallel to the a axis. The quaternary ammonium ions, each attaining C(s) molecular symmetry, are laterally attached by donor hydrogen bonds to the exposed water molecules of the zigzag chain. The crystal structure consists of layers each having a zipper-like arrangement of the quaternary ammonium "side-chains".