Crystal structures of dihydroxyacetone and its derivatives

Abstract

The crystal and molecular structures of three crystalline forms of the dihydroxyacetone dimer, C 6H 12O 6, DHA-dimer: α ( 1a), β ( 1b), and γ ( 1c), the hydrated calcium chloride complex of dihydroxyacetone monomer, CaCl 2(C 3H 6O 3) 2·H 2O, CaCl 2(DHA) 2·H 2O ( 2a), the tetrahydrated calcium chloride complex of dihydroxyacetone monomer, CaCl 2(C 3H 6O 3)·4H 2O, CaCl 2(DHA)·4H 2O ( 2b), the dihydroxyacetone monomer, C 3H 6O 3, DHA ( 2c), and dihydroxyacetone dimethyl acetal, C 5H 12O 4, (MeO) 2DHA ( 3) are described. Compounds 1a and 2b crystallize in the triclinic system, and 1b, c, 2a, c, and 3 are monoclinic. Molecules of all forms of dihydroxyacetone dimer 1a, b, and 1c are the trans isomers, with the 1,4-dioxane ring in the chair conformation and the hydroxyl and hydroxymethyl groups in axial and equatorial dispositions, respectively. The Ca 2+ ions in 2a and 2b are bridged by the carbonyl O atoms from two symmetry-related DHA molecules to form centrosymmetric dimers with Ca⋯Ca distance of 4.307(2) Å in 2a and 4.330(2) and 4.305(2) Å in two crystallographically independent dimers in 2b. DHA molecules coordinate to the Ca 2+ ions by hydroxyl and carbonyl oxygen atoms. The eight-coordinate polyhedra of Ca 2+ are completed by water molecule and Cl − ion in 2a and by four water molecules in 2b. The dihydroxyacetone molecules in 2a, b, and 2c are in an extended conformation, with both hydroxyl groups being synperiplanar ( sp) to the carbonyl O atom. All hydroxyl groups in 2c (along with water molecules in 2a and 2b) are involved as donors in medium strong and weak intermolecular O–H⋯O hydrogen bonding. Some of them, as well as carbonyl O atoms or Cl − ions in 2a and 2b, act as acceptors in C–H⋯O (and C–H⋯Cl) hydrogen interactions.