PHENOLPHTHALEIN AND 3',3''-DINITROPHENOLPHTHALEIN

Phenolphthalein, C20H14O4, crystallized in the noncentrosymmetric spac e group Pna2(1) with two crystallographically inequivalent molecules. Each of these is linked to four others of its own type by four hydroge n bonds having O-donor... O-acceptor distances ranging from 2.631(4) t o 2.787(4) Angstrom. While chains of hydrogen bonds propagate in a num ber of directions in this structure, cyclic hydrogen bonding is not ob served. 3',3''-Dinitrophenolphthalein, C20H12N2O8, crystallized in the centrosymmetric space group Pbcn with a single molecule in the asymme tric unit. Each molecule is linked to three others by four hydrogen bo nds having O-donor... O-acceptor distances ranging from 2.572(4) to 3. 274(3) Angstrom. Although chains of hydrogen bonds are prominent in th is structure, cyclic hydrogen bonding also occurs and forms dimers. As expected on the basis of the excess of potential acceptor O atoms ove r donors in both structures, significant C-H ... O interactions are al so abundant.