- The photodimerisation of the α- and β-forms of trans-cinnamic acid: A study of single crystals by vibrational microspectroscopy
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Infrared and Raman microspectroscopy have been used to follow the photodimerisation reactions of single crystals, the α- and β-forms of trans-cinnamic acid. This approach allows the starting materials and products - α-truxillic acid that has Ci symmetry and β-truxinic acid, which has Cs symmetry - to be identified. It also allows the topotactic nature of the reaction to be confirmed. Attempts to produce the poorly-defined unreactive γ-form of trans-cinnamic acid resulted only in a mixture of the α- and β-forms. The findings suggest a wide role for these spectroscopic methods in monitoring solid-state organic reactions.
- Atkinson, Samantha D.M.,Almond, Matthew J.,Hollins, Peter,Jenkins, Samantha L.
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- Reversible cross-linking of aliphatic polyamides bearing thermo- and photoresponsive cinnamoyl moieties
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Photosensitive polymers have gained strong attention in development of different polymeric systems for diverse applications. Particular attention is paid to polymers with cinnamoyl groups either in polymer backbone or in pendent position owing to their excellent photoreactivity and thermoreactivity upon UV light irradiation or heating. This work aims at synthesizing a novel photo- and thermosensitive aliphatic polyamide by anionic ring-opening copolymerization of ε-caprolactam and α-cinnamoylamido-ε-caprolactam. The photochemical reversible cross-linking of solutions and thermal cross-linking of spin-coated films made up of these new cinnamoyl-functionalized polyamides were monitored by UV-vis spectroscopy. These aliphatic polyamide copolymers were characterized by magic angle spinning solid-state NMR, and their thermal behaviors were studied by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis.
- Tunc, Deniz,Le Coz, Cedric,Alexandre, Michael,Desbois, Philippe,Lecomte, Philippe,Carlotti, Stephane
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- Competitive isomerization and dimerization in co-crystals of 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol and sorbic acid: A new look at stereochemical requirements for [2+2] dimerization
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Competitive [2+2] photodimerization and E→Z isomerization reactions occur in a co-crystal of 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol upon irradiation with 325 nm light. At 90 K both reactions are observed, whereas at 280 K the dimerization reaction is very fast and inhibits isomerization as the nature of the chromophore is affected by the reaction. The temperature dependence of the stereospecificity of the dimerization reaction is related to the large sliding motion required to bring the reacting molecules into juxtaposition. The progress of the reactions has been monitored by photocrystallographic methods. The Royal Society of Chemistry.
- Zheng, Shao-Liang,Pham, Oanh,Vande Velde, Christophe M. L.,Gembicky, Milan,Coppens, Philip
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- Nickel-Catalyzed Reductive [2+2] Cycloaddition of Alkynes
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The nickel-catalyzed synthesis of tetrasubstituted cyclobutenes from alkynes is reported. This transformation is uniquely promoted by the use of a primary aminophosphine, an unusual ligand in nickel catalysis. Mechanistic insights for this new transformation are provided, and postreaction modifications of the cyclobutene products to stereodefined cyclic and acyclic compounds are reported, including the synthesis of epi-truxillic acid.
- Ca?ellas, Santiago,Montgomery, John,Pericàs, Miquel à.
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p. 17349 - 17355
(2019/01/04)
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