ESR study of reactions of cellulose with ·OH generated by Fe⁺²/H₂O₂

Abstract

SynopsisIt was demonstrated by ESR spectroscopy that the Fe+2/Hz0z syst,em gave a reactive species which generated an ESR triplet spectrum or sorbitol similar to that generated by hydroxyl radicals from the Ti+3/Ha03 system. An ESR spectrum was obtained for the hydroxyl radicals generated by the latter system. However, the lifetime of hydroxyl radicals, generated by the Fe+2/Hz0z system, was apparently very short, and an ESR spectrum for the hydroxyl radicals, generated by this system, was not observed. The Fe+z/HzOz system also generated triplet spectra with cotton cellulose I, cotton cellulose 11, and microcrystalline cellulose, suggesting that a hydrogen at.om had been abstracted from the hydroxyl group on carbon C , or possibly the hydrogen atom on carbon Cg.The ESR spectrum generated on microcrystalline cellulose was less intense than those generat,ed on cellulose I and 11. On initiation of graft polymerization of the activated celluloses with acrylonitrile, the triplet spectrum disappeared and was replaced by two strong singlet spectra. One of the singlet spectra was likely generated on carbon C1 or C, on depolymerization of the cellulose molecule, and the other was probably generated on the end of the growing polyacrylonitrile molecular chain. The absence of a triplet spectrum gave direct evidence for the order in which the acrylonitrile monomer was being grafted onto the cellulose molecule. The mechanisms proposed by Haber and Weiss for the reactions generated in the Fe + 2 / H~0 z system were generally supported.

ESR Spectroscopy in Polymer Research

“…ESR studies of the reaction of cellulose with hydroxy radicals generated by Fe 2+ -H202 in a flow system, have been described by Arthur et al 76 ). It has been suggested, considering ESR spectrum shown in Figure 5.86, that hydrogen atoms 5.…”

Vinyl Cellulose Copolymers

“…; droxyl radicals, in a separate reaction, for example, in the ferrous ion-hydrogen peroxide system, which . abstract hydrogen atoms from cellulose to leave freeradical sites on the cellulose molecule [ 14 ] . _ Using electron spin resonance (ESR) spectroscopy, we have investigated these methods and the copolymerization reactions of the activated celluloses with acrylonitrile.…”

“…reaction when the free-radical sites were formed. Analyses of ESR spectra indicated that with ceric ions the radicals were likely formed at carbon C2 arid/or Cs and that with ferrous ion-hydrogen peroxide the radicals were likely formed at carbon C6 and/or C6 [2,14] . Also, in using methods VI and VII, it was likely that the free-radical sites were formed in the less ordered areas of the cotton fiber.…”

“…The graft copolymerization reactions of acrylonitrile with cotton have been initiated at free radical sites formed on the cellulose molecule by interaction with high-energy radiation [ 3-5, 7-13, 15-19, 21, 22], by reaction with ceric ions in an acidic medium [ 2, ~ 9, 28], or by formation of hydroxyl radicals in a separate reaction [14,28], such as in ferrous ionhydrogen peroxide solution which abstracted a hydrogen atom from the cellulose molecule. We have shown that the molecular weight of the grafted copolymer was dependent on the experimental conditions of the copolymerization reaction ( 7,28 ] .…”

“…In recent years, some work has been done on polyamides and corresponding model compounds in order to explain the course of the oxidative degradation of nylon [3,11,14,19] . Most of this work is concerned with photo-oxidation, and little has been done on the oxidation of nylon in the presence of oxygen and water at temperatures below 100°C.…”