Xanthene-9-carboxylic Acid

In xanthene-9-carboxylic acid, C₁₄H₁₀O₃, hydrogen bonding is of the cyclic dimer type but involves two crystallographically inequivalent molecules and does not occur about a center of symmetry. The carboxylic H atoms are ordered. The dihedral angle (fold angle) of the xanthene core is 14.2 (1)° for molecule A and 11.3 (2)° for molecule B. The planes of the carboxyl groups are almost perpendicular to the xanthene cores.

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