Paper
Photochemical Reduction of Nitrobenzene and Its Reduction Intermediates. IX. The Photochemical Reduction of 4-Nitropyridine in a Hydrochloric Acid-Isopropyl Alcohol Solution
Published Apr 1, 1971 · S. Hashimoto, K. Kano, K. Ueda
Bulletin of the Chemical Society of Japan
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Abstract
The photochemical reduction of 4-nitropyridine has been investigated in hydrochloric acid-isopropyl alcohol solutions. 4-Nitropyridine was not photoreduced in isopropyl alcohol, whereas when the photolysis was carried out in hydrochloric acid-isopropyl alcohol solutions, the photoreduction of 4-nitropyridine proceeded from its n,π* triplet state to give 4-hydroxylaminopyridine in a quantitative yield. The quantum yields for the disappearance of 4-nitropyridine in hydrochloric acid-isopropyl alcohol solutions increased with the concentration of hydrochloric acid up to 3.6×10−2 mol l−1 (Φ=0.27–0.94). These results suggest that the hydrogen abstraction of photoexcited 4-nitropyridine proceeds electrophilically because of the decrease in the electron density of the nitro group, in decrease resulting from the protonation of heterocyclic nitrogen and the n,π* excitation of the nitro group.
Photochemical reduction of 4-nitropyridine in hydrochloric acid-isopropyl alcohol solutions produces 4-hydroxylaminopyridine in a quantitative yield, with hydrogen abstraction occurring electrophilically due to decreased electron density of the nitro group.
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