Structure, solid-state reactions and polymorphism of molecular crystals

This thesis reports an investigation of the crystal structures and solid-state reactivity of unsaturated carbonyl compounds. Chapter One contains a summary of the research reported in this thesis. Chapter Two reports an investigation of the solid-state reactivity of three nitrogen base/propynoic acid co-crystalline systems. The three co-crystals or co-crystalline salts studied are 4-dimethyl aminopyridinium propynoate, pyrazolium propynoate propynoic acid and 2-pyridone propynoic acid. Upon heating, all three materials undergo a high yield Michael addition reaction, with a trans-substituted acrylic acid or acrylate as the major product. 4-Dimethylaminopyridinium propynoate and 2-pyridone propynoic acid are stable to 60Co gamma-irradiation even though the crystal structures reveal short acetylene · · · acetylene contacts. Chapter Three explores the crystal structures and hydrogen bonding motifs of four substituted benzoic acid/2-pyridone co-crystals. The four co-crystals studied are 4-hydroxy-benzoic acid/2-pyridone, 4-amino-benzoic acid/2-pyridone, 3,5-dinitrobenzoic acid/2-pyridone and 4-amino-3,5-dinitrobenzoic acid/2-pyridone. Inspection of the crystal structures of the four co-crystals shows that the first two co-crystals form an acid-pyridone hydrogen bonded dimer, whereas the last two co-crystals form a self-complementary pyridone-pyridone hydrogen bonded dimer. Chapter Four reports charaterization of two polymorphs of methacrylamide. Methacrylamide crystallizes as concomitant conformational polymorphs. Crystal structures of the two polymorphs indicate that the monoclinic form contains only the s-cis conformer, while the orthorhombic form contains only the s-trans conformer. The two polymorphs are further characterized by PXRD, DSC, FTIR and Raman spectra. DSC analysis indicates an enantiotropic relationship between the two polymorphs, with the monoclinic form as the stable form. Chapter Five reports an investigation of the crystal structures and gamma-irradiation of diaquabis(4-pentenoato)zinc and bis(4-pentenoato)barium. Both crystalline materials undergo solid-state polymerization upon gamma-irradiation. Bis(4-pentenoato)barium has a reaction pathway which suggests the formation of the isotactic polymer, while diaquabis(4-pentenoato)zinc has a reaction pathway which suggests the formation of the syndiotactic polymer.