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Photoreactions of 1,4‐Naphthoquinones: Effects of Substituents and Water on the Intermediates and Reactivity ¶
Author(s) -
Görner Helmut
Publication year - 2005
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2005.tb00197.x
Subject(s) - chemistry , photochemistry , intramolecular force , naphthoquinone , semiquinone , quinone , reactivity (psychology) , radical , nucleophile , medicinal chemistry , triplet state , stereochemistry , molecule , organic chemistry , catalysis , medicine , alternative medicine , pathology
The photochemistry of lapachol and other 1,4‐naphthoquinone (NQ) derivatives, e.g. 2‐methoxy‐1,4‐naphthoquinone (MeONQ), 2‐hydroxy‐1,4‐naphthoquinone (2‐HONQ) or 5‐hydroxy‐1,4‐naphthoquinone (5‐HONQ) and 2‐methyl‐5‐hydroxy‐1,4‐naphthoquinone (P‐NQ) in solution at room temperature was studied by ultraviolet‐visible spectroscopy after nanosecond laser pulses at 248 nm. The triplet state and semiquinone radicals were observed for MeONQ, HONQ and P‐NQ, whereas for lapachol, intramolecular H‐atom and charge transfer processes take place, as in the case of vitamin K 1 . The photoinduced reaction of NQ into HONQ is initiated by nucleophilic water addition to the triplet state, and for the secondary reactions, a modified mechanism is proposed.