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Molecular Arrangement and Photoreaction of Sorbamides and Hexadienyl Carbamates with Various N-Substituents in the Solid State

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posted on 2007-07-03, 00:00 authored by Yutaka Mori, Tsuyoshi Chiba, Toru Odani, Akikazu Matsumoto
The crystal structure and solid-state photoreaction of sorbamides and 2,4-hexadienyl carbamates with various N-substituents have been investigated. One-dimensional (1D) hydrogen bond chains with a repeating distance of 5 Å were observed in their crystals, due to the strong intermolecular interaction between the CO and N−H groups in the amide and carbamate moieties. We have revealed that N-benzylsorbamide and 2,4-hexadienyl N-(1-naphthyl)carbamate have a molecular stacking structure appropriate for the occurring [2+2] photodimerization and topochemical polymerization, respectively. The former sorbamide derivative gave a cyclodimer with an asymmetric structure, which was determined by NMR spectroscopy, under UV irradiation in the crystalline state. The γ-radiation of the latter carbamate derivative gave a polymer that is insoluble in any solvent. The polymer structure was determined by powder X-ray diffraction and IR spectroscopy. The reactivity in the solid-state photoreaction was discussed on the basis of the molecular stacking structures such as the stacking distance, the carbon-to-carbon distance, and the overlap of the π-orbitals. A twisted molecular conformation of the reacting diene planes against the carbamoyl planes connected with each other by the 1D hydrogen bonding is important for topochemical polymerization in the solid state.