LOW-TEMPERATURE CRYSTAL-STRUCTURE AND MOLECULAR-CONFORMATION OF L-(+)-LACTIC ACID

L-(+)-Lactic acid, C3H6O3, M(r) = 90.08, orthorhombic, P2(1)2(1)2(1), a = 5.4896(3), b = 8.4221(3), 9.3453(5)angstrom, V = 432.07(4)angstrom3, Z = 4, D(x) = 1.385 g cm-1, lambda(MoKalpha) = 0.71073 angstrom, mu = 1.2 cm-1, F(000) = 192. Diffraction data have been collected at 100 K and the structure has been solved by direct methods to R = 0.030 for 976 unique observed data. The hydroxyacetic acid moiety of the molecule is almost planar with the aliphatic hydroxy-group oxygen atom at the side of the carbonyl oxygen atom of the carboxy group. The two hydroxy groups are involved in intermolecular hydrogen bonding. The aliphatic hydroxy group forms a bifurcate planar hydrogen-bond configuration in which the aliphatic hydroxy and acid carbonyl oxygen atoms of a symmetry-related molecule participate as acceptors. The acidic hydroxy group donates an intermolecular hydrogen bond to the aliphatic hydroxy-group oxygen atom.