Aki Yoshioka, Teruyuki Seino, Masayoshi Tabata, Mitsuo Takai
Homolytic Scission of Interunitary Bonds in Lignin Induced by Ultrasonic Irradiation of MWL Dissolved in Dimethylsulfoxide
Summary
An electron spin resonance (ESR) method combined with a spin trapping technique was applied to trap
and characterize unstable radicals which were generated by ultrasonic irradiation of the dimethylsulfoxide
(DMSO) solution of a softwood, Yezo Spruce (Picea jezoensis carr.) lignin. It was found that an
unstable secondary carbon radical, ~CH ? in the solution was trapped as the stable nitroxide spin adduct
when the DMSO solution was subjected to ultrasonic irradiation in the presence of a spin trapping
reagent: 2,4,6-tri-tert-butylnitrosobenzene (BNB) at 50°C for 30 min. This means that the alkyl phenyl
ether bonds, ~CH-O-phenyl, known as interunitary bonds in lignins were homolytically cleaved by the
ultrasonic irradiation, although the phenoxy radical Ph-O ?, called guaiacoxy radical, i.e. the counter radical
of the secondary carbon radical, was not trapped by the BNB spin trap. This suggests that the trapping
of the guaiacoxy radical, having a methoxy group in an ortho-position, by the BNB molecule, carrying
two bulky butyl groups in the ortho-positions, is sterically hindered.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 07/2000
Pages: 357 - 364
Show full article (external site)
Show all available items of this journal
Search
