L -Threonine at 12 K

The crystal structure of l-threonine, C4H9NO3, was redetermined at 12 K. The present X-ray data allowed the determination of more accurate molecular geometry and of all the H-atom positions. The precision of the C—C, C—N and C—O distances is 0.002 Å or better, while that of the H-atom distances is 0.02 Å. The shape of the molecule relative to the Cα—Cβ bond corresponds to the staggered (D3 d) conformation, with the H atoms at Cα and Cβ trans to each other, yielding the least-crowded molecular conformation. All H atoms of the NH3 and OH groups are involved in intermolecular hydrogen bonds, which interconnect the molecules to form a three-dimensional network.