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Wood Chemistry PSE 406/Chem E 470

Wood Chemistry PSE 406/Chem E 470. Lecture 9 Lignin Biosynthesis. Class Agenda Lignin I. Basic Lignin Biosynthesis Nomenclature Methoxyl Groups Phenoxy Radical Formation Radical Coupling. Random Lignin Information.

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Wood Chemistry PSE 406/Chem E 470

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  1. Wood ChemistryPSE 406/Chem E 470 Lecture 9 Lignin Biosynthesis PSE 406 Lecture 9

  2. Class AgendaLignin I • Basic Lignin Biosynthesis • Nomenclature • Methoxyl Groups • Phenoxy Radical Formation • Radical Coupling PSE 406 Lecture 9

  3. Random Lignin Information • Anselme Payen 1838: Reacts wood with nitric acid and then sodium hydroxide. Undissolved material he names cellulose. • Schulze 1857: Names dissolved material lignin from the Latin lignum meaning wood. • Phenolic Polymer - The Glue that Holds the Fibers Together • Polydisperse (Large and Small Polymers) • 3 Dimensional Networks - Branched Polymer PSE 406 Lecture 9

  4. Lignin Biosynthesis I Notes PSE 406 Lecture 9

  5. Lignin Biosynthesis II Notes PSE 406 Lecture 9

  6. Lignin BiosynthesisNomenclature Side Chain Notes } Phenylpropane Unit C9 Common Names PSE 406 Lecture 9

  7. Lignin StructureMethoxyl Content Notes PSE 406 Lecture 9

  8. Lignin BiosynthesisNomenclature • Once incorporated into lignin, the ring structures of the precursors are given these names. PSE 406 Lecture 9

  9. Lignin BiosynthesisEnzymatic Formation of Phenoxy Radical • The initial step in the polymerization of lignin is an enzymatic directed one electron abstraction forming a phenoxy radical. Notes PSE 406 Lecture 9

  10. Lignin BiosynthesisResonance Forms of Phenoxy Radical • The phenoxy radical is only one of several resonance structures. • This figure shows a second resonance structure with the free radical on the 5 carbon of the ring. PSE 406 Lecture 9

  11. Lignin BiosynthesisResonance Forms of Phenoxy Radical Notes PSE 406 Lecture 9

  12. Lignin Coupling-O-4 Notes PSE 406 Lecture 9

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