Crystal and molecular structure of 3-hydroxy-5-phenylisoxazole (α form)

The crystal structure of the α form of 3-hydroxy-5-phenylisoxazole has been determined from three-dimensional X-ray data. The crystals are monoclinic, space group P2₁/n with four molecules in the unit cell. The cell dimensions are: a = 10.41(2); b = 3.89(1); c = 19.14(4) Å; β = 96.1° (3). The structure was refined by the block-diagonal least-squares method to a final R value of 0.080 for 1111 observed reflections. The molecular dimensions are in good overall agreement with those in β form, while the packing is markedly different. Conjugation and planarity in the molecule are discussed.