Reaction with ozonized lignin

Many of the chemical reactions used to modify lignosulfonates are also used to modify kraft lignins. These include ozonation, alkaline—air oxidation, condensation with formaldehyde and carboxylation with chloroacetic acid (100), and epoxysuccinate (101). In addition, cationic kraft lignins can be prepared by reaction with glycidjiamine (102). 

Kratzl K, Claus P, Reichel G (1976) Reactions of lignin and lignin model compounds with ozone TAPPI 59(11) 86-87... 

M Ragnar, T Eriksson, T Reitberger, P Brandt. A new mechanism in the ozone reaction with lignin like strnctnres. Holzforschung 53 423-428, 1999. 

H Kaneko, S Hosoya, J Nakano. Degradation of lignin with ozone Reactions of biphenyl and a-carbonyl type model compounds with ozone. Mokuzai Gakkaishi 27 678-683,... 

The aromatic ring of a phenoxy anion is the site of electrophilic addition, eg, in methylolation with formaldehyde (qv). The phenoxy anion is highly reactive to many oxidants such as oxygen, hydrogen peroxide, ozone, and peroxyacetic acid. Many of the chemical modification reactions of lignin utilizing its aromatic and phenoHc nature have been reviewed elsewhere (53). 

Miksche, G. E. Lignin reactions in alkaline pulping processes (rate processes in soda pulping). In Chemistry of Delignification with Oxygen, Ozone, and Peroxides Nakano, J. Singh, R. P.,Eds. Uni Publishers Co Tokyo, Japan, 1980 pp. 107-120. 

Dence, C. W. In Reactions of Hydrogen Peroxide with Lignin Current Status in Chemistry of Delignification with Oxygen, Ozone and Perox-... 

Other processes in which the aromatic ring is modified via electrophilic substitution reactions are nitration and ozonation. The electrophilic substitution of nitro groups on the aromatic moiety of lignin and accompanying reactions have been reviewed by Dence (1971). A nitration process consisting of the pretreatment of chemical pulp with nitrogen dioxide followed by treatment... 

Dorland et al (1939) used 95% formic acid in water and Miura et al (1985) 50% formic acid in dichloromethane as reaction media In the latter study, the results were not strikingly different from those obtained using acetic or propanoic acids in parallel experiments, even though formic acid is known to be consumed by ozone in dilute aqueous perchloric acid This finding is also consistent with the appearance of formic acid as a lignin ozonation product Bonnet et al (1989) found that up to 36% of the total acidity that developed on ozonation of alkali lignin in water was due to the presence of formic acid... 

The choice of liquid phase can affect the course of ozonation. This has been shown with phenylindenes by Miura et al. (1985) and with lignin models by Kratzl et al. (1976), who found that 4-methylveratrole gave a higher yield of dimethyl -methyl-cis,cis-muconate in 45% aqueous acetic acid than in dichloromethane and that the yield of dimethyl oxalate from acetoveratrone was markedly dependent on the solvent. Eriksson and Gierer (1985) found that in methanol the benzene ring of vanillin is cleaved (albeit only very slowly, after acetalization has occurred), but that in nonprotic solvents, such as acetone, the initial reaction is oxidation of the aldehyde function to a carboxyl group. 

DC Johnson. Lignin reactions in delignification with peroxyacetic acid. In RP Singh, J Nakano, JS Gratzl, eds. Chemistry of Delignification with Oxygen, Ozone and Peroxides. Uni Publishers Co., Ltd., Tokyo, 1980, pp. 217-228. 

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