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Photolysis of acetophenone derivatives with α‐cyclopropyl substituents
Author(s) -
Ranaweera Ranaweera A. A. Upul,
Weragoda Geethika K.,
Bain John,
Watanabe Shinji,
Abe Manabu,
Gudmundsdottir Anna D.
Publication year - 2015
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3389
Subject(s) - chemistry , ketyl , flash photolysis , photochemistry , acetophenone , ketone , reaction rate constant , photodissociation , benzophenone , medicinal chemistry , quenching (fluorescence) , organic chemistry , fluorescence , kinetics , physics , quantum mechanics , catalysis
Laser flash photolysis of cyclopropyl(phenyl)methanone 6 in argon‐saturated methanol yields the triplet ketone (T 1K ) of 6 that is formed with a rate constant of ~1.7 × 10 7 s −1 ( λ max = 360 nm) and has a lifetime of ~1.4 µs. T 1K of 6 decays to form ketyl radical 7 ( λ max ~300 nm), which dimerizes to form photoproducts, pinacol derivatives 8 and 9. In comparison, photolysis of trans ‐phenyl(2‐phenylcyclopropyl)methanone 1 in argon‐saturated chloroform‐d results in cis ‐phenyl(2‐phenylcyclopropyl)methanone 2 and a smaller amount of 3, presumably through 1,3‐biradical 11. Nanosecond laser flash photolysis of 1 does not reveal significant transient absorption, although the T 1K of 1 is detected with phosphorescence at 77 K. Density functional theory calculations were used to elucidate the triplet reactivity of 1, 2 and 6 by comparing the feasibility of H atom abstraction, cyclopropyl cleavage and β‐quenching of their triplet ketones. Copyright © 2014 John Wiley & Sons, Ltd.