The crystal structure of thiamine hydrochloride (vitamin B)

Abstract

The crystal structure of thiamine hydrochloride has been determined by three-dimensional Patterson superposition methods and refined by full-matrix least-squares computations to a final R factor of 8.0% for 3039 reflections with measurable intensities. The unit cell is monoclinic, space group P21/c, with a-6-99, b = 20.59, c = 12.73/~ and fl = 114.0 °. The locations of 17 out of 20 hydrogen atoms in the asymmetric unit have been determined from a difference-Fourier synthesis and ~n attempt has been made to refine the coordinates of these hydrogen atoms by least squares. The pyrimidine portion of the molecule is protonated at the ring nitrogen opposite the amino group. The planes of the thiazolium and pyrimidine rings are at a dihedral angle of 76 °, and are turned so as to bring the amino group closer to the hydrogen-bearing carbon of the thiazolium ring. The structure contains two weak but distinct C-H • • • C1-hydrogen bonds.