Laser flash photolysis studies on radical formation by H-atom abstraction of triplet vitamin K3 and by H-atom transfer via the triplet exciplex between triplet methyldihydroxynaphthalene and benzophenone

Laser flash photolysis studies on radical formation by H-atom abstraction of triplet vitamin K3... Nanosecond laser photolysis techniques were incorporated to obtain (1) the absorption spectra and coefficients of triplet vitamin K3 (2-methyl-1,4-naphthoquinone, MNQ) and its ketyl radical (2-methylnaphthosemiquinone, 2MNQH*) in acetonitrile (ACN) as well as to reveal (2) the mechanisms for hydrogen atom abstraction of triplet MNQ (3MNQ*) from phenol which proceeded in a diffusion process with an efficiency of unity. On the other hand, the hydroxymethylnaphthoxy radical was produced with the benzophenone ketyl radical (BPK) by the hydrogen atom transfer from triplet 2-methyl-1,4-dihydroxynaphthalene (MDHNp) sensitized by triplet benzophenone to benzophenone (BP) via the triplet exciplex. The question to be addressed was, which was produced in the MDHNp-BP system, the 2-methyl or 3-methylnaphthosemiquinone radical? Comparing the absorption spectrum and coefficient of the radical produced via the triplet exciplex with those of the 2MNQH* obtained by H-atom abstraction of 3MNQ*, the radical formed with BPK was revealed to be 2MNQH*. The reasons for the preferable formation of 2MNQH* are discussed for H-atom abstraction as well as the transfer reactions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

Laser flash photolysis studies on radical formation by H-atom abstraction of triplet vitamin K3 and by H-atom transfer via the triplet exciplex between triplet methyldihydroxynaphthalene and benzophenone

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Publisher
Springer Netherlands
Copyright
Copyright © 1997 by Springer
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1163/156856797X00277
Publisher site
See Article on Publisher Site

Abstract

Nanosecond laser photolysis techniques were incorporated to obtain (1) the absorption spectra and coefficients of triplet vitamin K3 (2-methyl-1,4-naphthoquinone, MNQ) and its ketyl radical (2-methylnaphthosemiquinone, 2MNQH*) in acetonitrile (ACN) as well as to reveal (2) the mechanisms for hydrogen atom abstraction of triplet MNQ (3MNQ*) from phenol which proceeded in a diffusion process with an efficiency of unity. On the other hand, the hydroxymethylnaphthoxy radical was produced with the benzophenone ketyl radical (BPK) by the hydrogen atom transfer from triplet 2-methyl-1,4-dihydroxynaphthalene (MDHNp) sensitized by triplet benzophenone to benzophenone (BP) via the triplet exciplex. The question to be addressed was, which was produced in the MDHNp-BP system, the 2-methyl or 3-methylnaphthosemiquinone radical? Comparing the absorption spectrum and coefficient of the radical produced via the triplet exciplex with those of the 2MNQH* obtained by H-atom abstraction of 3MNQ*, the radical formed with BPK was revealed to be 2MNQH*. The reasons for the preferable formation of 2MNQH* are discussed for H-atom abstraction as well as the transfer reactions.

Journal

Research on Chemical IntermediatesSpringer Journals

Published: Apr 14, 2009

References

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