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Direct measurements of the rates of 1,3- and 1,5-sigmatropic hydrogen shifts in the photo-Fries rearrangements of phenyl acetate

✍ Scribed by Tadashi Arai; Seiji Tobita; Haruo Shizuka

Publisher: Elsevier Science
Year: 1994
Tongue: English
Weight: 513 KB
Volume: 223
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(94)80006-5

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✦ Synopsis

The rate constants for the 1,3-and 1,Mgmatropic hydrogen shifts of the phot&Fries rearranged intermediates of phenyl acetate produced by laser flash photolysis at 266 nm were directly measured in several solvents. The rate constant for the 1,3hydrogen shift (3.6 s-l) was faster than that for the l&shift (6.5 x lo-* s-') in the ground state in methylcyclohexane at 293 K, contrary to the expectation by the Woodward-Hoffmann rule. In protic solvents, ethanol and methanol, a remarkable increase in the rate constants ( -, lo5 s-l) was observed. A tentative mechanism including the role of the non-bonding electrons of the intermediates is discussed.

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