Naphthalene-1,8-dicarb-oxy-lic anhydride: a monoclinic polymorph.

A new type of naphthalene-1,8-dicarb-oxy-lic anhydride, C(12)H(6)O(3), was synthesized hydro-thermally. Unlike the two previously reported polymorphs, which crystallize in the ortho-rhom-bic space groups P2(1)2(1)2(1) [Shok et al. (1971). Kristallografiya, 16, 500-502; Grigor'eva & Chetkina (1975). Kristallografiya, 20, 1289-1290] and Pbca [Shok & Gol'der (1970). Zh. Strukt. Khim.11, 939-940], this present structure crystallizes in the monoclinic space group P2(1)/c. In this structure, the planar [total puckering amplitude Q = 0.0362 (15)] mol-ecules lie parallel to each other along the a axis.