Photoinduced Intramolecular Hydrogen Transfer Reaction of Ortho Nitrobenzyl Compounds

Hiroaki Takahashi,Masanori Tachikawa,Makoto Sakai,Yoshiki Watanabe

doi:10.1155/1999/29456

Hiroaki Takahashi, Masanori Tachikawa + Show 2 more

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https://doi.org/10.1155/1999/29456

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Journal: Laser Chemistry	Publication Date: Jan 1, 1999
Citations: 2	License type: CC BY 3.0

Affiliation: Waseda University

Abstract

Time-resolved resonance Raman and absorption spectra have revealed that the photoinduced intramolecular hydrogen transfer reaction of ortho nitrobenzyl compounds is initiated by the abstraction of methylene hydrogen by the ortho nitro group to generate the ortho aci-nitro acid isomer. In polar solvents the ortho aci-nitro acid is dissociated into the aci-nitro anion and a proton, and the proton is captured by other hydrogen accepting sites, such as 2-pyridyl, 4-pyridyl and 4-nitro groups to generate the ortho N—H quinoid, para N—H quinoid and para aci-nitro acid isomers, respectively. For 2-nitroethylbenzene and 2- and 4-(2′-nitrobenzyl)pyridines the structure of the aci-nitro anion is very similar to that of their respective ortho aci-nitro acid, while for 2,4-dinitroethylbenzene the structure of the aci-nitro anion quite resembles that of the para aci-nitro acid.

Highlights

Benzyl derivatives having a nitro group at the ortho position are known to undergo photoinduced reversible intramolecular transfer of methylene hydrogen of the benzyl group
Time-resolved resonance Raman and absorption spectra have revealed that the photoinduced intramolecular hydrogen transfer reaction of ortho nitrobenzyl compounds is initiated by the abstraction of methylene hydrogen by the ortho nitro group to generate the ortho aci-nitro acid isomer
In polar solvents the ortho aci-nitro acid is dissociated into the aci-nitro anion and a proton, and the proton is captured by other hydrogen accepting sites, such as 2-pyridyl, 4-pyridyl and 4-nitro groups to generate the ortho N--H quinoid, para N--H quinoid and para aci-nitro acid isomers, respectively

Summary

Introduction

Benzyl derivatives having a nitro group at the ortho position are known to undergo photoinduced reversible intramolecular transfer of methylene hydrogen of the benzyl group. Time-resolved resonance Raman and absorption spectra have revealed that the photoinduced intramolecular hydrogen transfer reaction of ortho nitrobenzyl compounds is initiated by the abstraction of methylene hydrogen by the ortho nitro group to generate the ortho aci-nitro acid isomer. This band is assignable to the ortho aci-nitro acid isomer generated by hydrogen transfer from the methylene group to the ortho nitro group.

Results

Conclusion