A crystallographic investigation of the structures and hydrogen bonding properties of two substituted hydantoins

Crystals of 5,5-dimethylhydantoin are orthorhombic, space group P2₁2₁2₁, with a = 7.216(2), b = 7.203(1) and c = 13.005(4) Å. Full matrix least-squares refinement has yielded an R value of 0.042 for the 777 observed reflections. The molecules are held together by stacking interactions and by hydrogen bonds between N(1) and 0(6). 0(7) apparently does not participate in hydrogen bonding.

Crystals of the 1:1 molecular complex of 9-methyladenine and 2-thiohydantoin are monoclinic, space group C2/c, with a = 21.140(3), b = 7.085(1), c = 16.101(2) Å and β = 103.27(2)°. Full matrix least-squares refinement has yielded an R value of 0.035 for the 2475 observed reflections. The crystal structure consists of ribbons with alternating adenine and hydantoin moieties linked via (hydantoin)N-H----N(adenine) hydrogen bonds. The inter-ribbon association is via N-H----N hydrogen bonds involving self-paired 9-methyladenine molecules. This interaction is of interest in that the adenine molecules are not coplanar, but rather form a dihedral angle of 47.9°. The sulfur and oxygen atoms of the 2-thiohydantoin molecules do not appear to act as acceptors in strong hydrogen bonds.