Lignin, photodegradation

Castellan, A., Colombo, N., Fomier de Violet, Nourmamode, A., and bouas-Laurent, H., "Photodegradation of Lignin A Photochemical Study of Bleached CTMP and Lignin Model Molecules", Proceedings of the 5th International Symposium of Woos and Pulping Chemistry, Raleigh, N.C., 1989, p.421-. 

Kringstad, K.P., Lin, S.Y., "Mechanism in the Yellowing of High-Yield Pulps by Light. Structure and Reactivity of Free Radical Intermediates in the Photodegradation of lignin", Tappi, 1970, 53(12), 2296. 

Photolysis of lignin n - Oxidative Photodegradation of Dioxane-Lignin", Polymer Photochem., 1986, 7, 461. 

Vanucci, C., Fomier de Violet, P., Bous-Laurent, H., Castellan, A., Photodegradation of Lignin. "A Photophysical and Photochemical Study of Non-phenolic a-Carbonyl 0-O-4 Lignin Model Dimer 3,4-Dimethoxy-a-(2 -methoxyphenoxy)acetophenone", J. Photochem. Photobiol., A Chem., 1988, 41, 251. 

Schmidt, J.A., Berinstain, A.B., de Rege, F., Heitner, C., Johnston, L.J., Scaiano, J.C. "Effect of Solvent on the Photodegradation of a-Guaiacoxyacetoveratrone, A Phenacyl-a-Aryl Ether Lignin Model" In Paper Lignocellulosics, Science, Technology, Development and Use Kennedy, J.F., Philips,G.O. and Williams, P.A. eds , Ellis Harwood Limited, N. Y., p.587. 

Berinstain, A.B. In Singlet State Participation and Solvent Effects on the Photodegradation of a-guaiacoxyacetoveratrone, a Lignin Model Compound Concordia University, Institute for Co-operative Education, Department of Chemistry and Biochemistry Work Term Report 1990. 

Lignin and lignin-related model compounds are subject to air oxidation and photodegradation, particularly in a dilute, alkaline solution. It is strongly recommended that a fresh solution of the sample be prepared immediately before making spectral measurements. The following precautions should be taken in the preparation of solutions ... 

Krmgstad KP, Lin SY (1970) Mechanism in the yellowing of high-yield pulps by light Structure and reactivity of free radical intermediates in the photodegradation of lignin TAPP1 53 2296-2301... 

The bulk chemical composition of seawater DOM (Table 8.8), however, is not consistent with a predominant riverine origin. In particular, seawater DOM is depleted in C and enriched in C and compared with most DOM discharged by rivers (with the Amazon being taken here as an example). Seawater DOM is also depleted in aromatic carbon (as measured by C NMR) and lignin phenol structural units (as determined by CuO oxidation), possibly as a consequence both of the low phenol content of marine plankton, and of selective alteration of aromatic carbon by photodegradation. Thus all evidence to date, including elevated total concentrations in surface marine waters (Fig. 8.19), indicates that seawater DOM is largely... 

These examples show the utility of using C NMR spectroscopy, dissolved lignin, and stable isotopes as molecular tracers of photodegradation of CDOM. Other tools of mass spectroscopy and compound separation and identification should provide additional information on changes to DOM as it is photodeg-raded. Recently, several groups have presented spectroscopic and spec-trophotometric methods for identification of chromophores [47-49,131]. 

C Vanned, P Pomier de Violet, H Bouas-Laurent, and A Castellan. Photodegradation of Lignin A Photophysical and Photochemical Study of a Nonphenolic a-carbonyl (3-0-4 Lignin Model Dimer, 3,4-dimethoxy-a-(2 -methoxyphenoxy)acetophenone. J. Photochem. Photobiol., A. Chem. 41 251-265, 1988. 

JA Schmidt, AB Berinstain, E de Rege, C Heitner, LJ Johnston, and JC Scaiano. Photodegradation of the Lignin Model a-guaiacoxyacetoveratrone. Unusual Effects of Solvent, Oxygen, and Singlet State Participation. Cart J. Chem. 69 104—107, 1991. 

K Konya and JC Scaiano. Development and Applications of Pyrene-Containing Fluorescent Probes for Monitoring the Photodegradation of Lignin-Rich Products. Chem. Mater. 6 2369-2375, 1994. 

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