Abstract
The crystal structure of the second polymorphic form of the title compound (α-form : Chem. Pharm. Bull., 30, 2629 (1982)) has been determined by X-ray diffraction analysis of a single crystal. The crystal of the β-form, C8H9FN2O3, is monoclinic, space group P21/n, with a=11.891 (5), b=14.556 (2), c=5.062 (1)Å, β=99.05 (2)°, U=865.3 (4)Å3, Mr=200.17, Z=4; Dc=1.54, Dm=1.54 gcm-3, F(000)=416, λ(Mo Kα)=0.7107Å, μ=1.433 cm-1. The structure was solved by the direct method using the MULTAN 78 program. Refinement by the full-matrix least-squares method gave a final R factor of 0.055 (1669 independent reflections). Bond lengths and angles agree well with those of both molecules in the α-form. The molecular conformation is very similar to one of those in the α-form. The cyclic dimer structure of the β-form is different from that of the α-form.
