Meclofenamic acid, C I4HIICI2NO2, probably the most
potent among analgesic fenamates, crystallizes in the
triclinic space group P1, with a = 8.569 (5), b =
8.954(8), c -- 9.371 (4) A, ct = 103.0 (2), fl --
103.5 (2), y = 92.4 (2) ° , Z = 2, D m = 1.43 (4), D c =
1.41 Mg m -3. The structure was solved by direct
methods and refined to R = 0.135 for 1062 observed
reflections. The anthranilic acid moiety in the molecule
is nearly planar and is nearly perpendicular to the
2,6-dichloro-3-methylphenyl group. The molecules, which exist as hydrogen-bonded dimers, have an internal hydrogen bond involving the imino and the carboxyl groups. The methyl group is disordered and occupies two positions with unequal occupancies. The disorder can be satisfactorily explained in terms of the rotational isomerism of the 2,6-dichloro-3-methylphenyl group about the bond which connects it to the anthranilic acid moiety and the observed occupancies on the basis of packing considerations