The Crystal Structures of Three Rhodanine-3-Carboxylic Acids

The rhodanine derivatives show various pharmacological activities. Rhodanine-3-carboxylic acids can be used as the substrates in various synthesis of compounds containing rhodanine-3-carboxyalkyl moiety. In this paper new crystal structures of rhodanine-3-acetic acid and its two homologues, i.e. rhodanine-3-propionic acid and rhodanine-3-butyric acid, are reported. The relationship between the length of the alkyl chain and the geometry of these molecules was studied. The crystal network is dominated by strong hydrogen bonds O-H center dot center dot center dot O formed by the carboxyl groups. Additionally, weak C-H center dot center dot center dot O and C-H center dot center dot center dot S contacts are observed. To study the difference in intermolecular interactions of rhodanine-3-carboxylic acid, three crystal structures were determined by X-ray diffraction method. The crystal network in all studied structures is built of homosynthons and stabilized by weak C-H center dot center dot center dot O and C-H center dot center dot center dot S contacts.