856367-49-2Relevant academic research and scientific papers
Toward the oxidative deconstruction of lignin: Oxidation of β-1 and β-5 linkages
Fang, Zhen,Meier, Mark S.
, p. 2330 - 2341 (2018/04/05)
There have been numerous reports on methods for the oxidative cleavage of β-O-4 linkages in lignin model compounds, but relatively few reports of how those methods affect other linkages that are present in lignin. We have investigated the effect of several of these oxidation methods on the β-1 and the β-5 lignin linkages, using four β-1 and β-5 model compounds. We observed that direct oxidative cleavage of C-C bonds occurs in metal-catalyzed TEMPO oxidation systems and with iron porphyrin oxidations, neither of which had we observed in similar oxidations on β-O-4 models. The β-5 linkage proved to be largely resistant to all of these oxidative systems, but the dihydrofuran ring in the β-5 model 3 was opened when treated with KMnO4 at elevated temperature. Most promising was the oxidation of 2 with DDQ, which produced the benzylic ketone in high yield (84%), as it does in reactions with β-O-4 models. This reaction exhibits selectivity for the benzylic position as well as compatibility with phenols, characteristics that are highly desirable for a two-step, benzylic oxidation/Baeyer-Villiger route for cleavage of lignin.
The Reactions of Lignin with Alkaline Hydrogen Peroxide. Part III. The Oxidation of Conjugated Carbonyl Structures
Gellerstedt, Goeran,Agnemo, Roland
, p. 275 - 280 (2007/10/02)
The alkaline hydrogen peroxide oxidation of aryl-α-carbonyl structures and cinnamaldehyde structures related to lignin has been studied using a kinetic method.Aryl-α-carbonyl structures in phenolic units are quantitatively cleaved to form the corresponding hydroquinone derivatives with rates of reaction strongly dependent on the substitution pattern in the aromatic ring.The presence of heavy metal ions like Fe(III) or Mn(IV) accelerates the oxidation but decreases the yield of hydroquinone.In nonphenolic units the oxidation of aryl-α-carbonyl structures is dependent upon the structure of the side chain.Cinnamaldehyde structures of the coniferaldehyde type are readily cleaved by alkaline hydrogen peroxide giving rise to the corresponding aromatic aldehyde.The reaction shows a first-order dependency on 2-> whereas -> has a negligible influence within the pH range studied.The significance of these results for the bleaching of mechanical pulps with alkaline hydrogen peroxide is briefly discussed.
