A low temperature study (30 K) of Form I 5 showed that the thiol group is ordered with regular S-H...S bonds and a N-C-C-S gauche (g+) dihedral angle of 70.6 • . However, a neutron diffraction study at room temperature showed disorder in the Form I lattice that can be modelled as either involving just the thiol hydrogens or modelled using both sulfur and hydrogen atoms.