STRUCTURE AND VIBRATIONAL-SPECTRA OF THE SOLID COMPLEX OF BETAINE-SULFURIC ACID MONOHYDRATE

The crystal structure of betaine-sulphuric acid monohydrate has been d etermined by X-ray diffraction as a monoclinic species of space group P2(1)/a, with a = 14.108(1) Angstrom, b = 11.702(2) Angstrom, c = 6.52 0(3) Angstrom, beta = 101.00(3) and Z = 4. The crystal comprises hydro gen-bonded units containing two bisulphate ions and two water molecule s linked in a ring, with a protonated betaine molecule attached to eac h of the bisulphate ions. Neighbouring units are linked by a hydrogen bond between a bisulphate ion and a water molecule. Powder FT-IR and R aman spectra were measured, and an assignment of the observed bands to vibrations of the hydrogen bonds and internal vibrations of the bisul phate ion and the betaine molecules is proposed. No evidence was found for any spectral changes in the vicinity of the phase transition prev iously reported at 253.7 K.