Competing processes in the photochemistry of picolines and their N-methyl salts: photoinduced charge transfer, phototransposition and photohydration
| Autor: | Vesna Blažek Bregović, Nikola Basarić |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
chemistry.chemical_classification
010405 organic chemistry Chemistry Radical Iodide Protonation General Chemistry Aziridine 010402 general chemistry Photochemistry 01 natural sciences 0104 chemical sciences chemistry.chemical_compound Excited state Pyridine Picoline Perchloric acid pyridine pyridinium salt excited state proton transfer excited state charge transfer phototransposition photohydration |
| Popis: | Photochemical reactivity of a series of picolines and their N-methylated salts has been investigated by preparative irradiations and UV–vis spectroscopy. Understanding competing photochemical processes and knowledge of their relative efficiencies is important in the application of pyridines as photocages or in the synthesis of complex polycycles. Contrary to previous reports for the gas phase, picolines are not reactive in the phototransposition, presumably due to protonation of the pyridine nitrogen in the excited state. Deuterium exchange was observed upon irradiation in CD3CN–D2O, but it was rationalized by photoionization and radical formation. On the other hand, N-methylated picoline salts are not protonated upon excitation. They undergo photohydration and phototransposition (Φ R = 0.01–0.06). Upon irradiation of iodides, azabicyclic [3.1.0] hydration products were obtained. A difference in product distribution was observed between iodides and perchlorates, due to photoelimination of perchloric acid leading to the thermal aziridine ring opening. Moreover, excitation of iodide derivatives gives rise to change transfer transition forming iodide radicals that eventually give I3 − with the quantum efficiency Φ R = 0.015–0.02. |
| Databáze: | OpenAIRE |
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