title: Trans-cinnamic acid and coumarin-3-carboxylic acid: experimental charge-density studies to shed light on [2 + 2] cycloaddition reactions.
abstract: As part of an ongoing series of experimental charge-density investigations into the intra- and intermolecular interactions present in compounds which undergo solid-state [2 + 2] cycloaddition reactions, the charge-density analyses of trans-cinnamic acid and coumarin-3-carboxylic acid are reported. Thus, high-resolution single-crystal X-ray diffraction data were recorded at 100 K for trans-cinnamic acid (sin theta/lambda(max) = 1.03 A(-1)) and coumarin-3-carboxylic acid (sin theta/lambda(max) = 1.19 A(-1)). In addition to the anticipated O-H...O hydrogen bonds weak C-H...O interactions were identified in both structures along with very weak intermolecular interactions between pairs of molecules that undergo solid-state [2 + 2] cycloaddition reactions upon irradiation.
authors.affiliation: Department of Chemistry, University Science Laboratories, Durham University, South Road, Durham DH1 3LE, England.
authors.forename: Judith A K
authors.initials: JA
authors.lastname: Howard
authors.forename: Mary F
authors.initials: MF
authors.lastname: Mahon
authors.forename: Paul R
authors.initials: PR
authors.lastname: Raithby
authors.forename: Hazel A
authors.initials: HA
authors.lastname: Sparkes
mesh_terms: D002934:Cinnamates / Q000737:chemistry* / Q000528:radiation effects*; D003374:Coumarins / Q000737:chemistry* / Q000528:radiation effects*; D018360:Crystallography, X-Ray; D003500:Cyclization; D004583:Electrons; D006860:Hydrogen Bonding; D008027:Light; D008958:Models, Molecular; D011789:Quantum Theory; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D002934:Cinnamates; D003374:Coumarins; C029010:cinnamic acid; C104227:coumarin-3-carboxylic acid