Cleavage of Ether Bonds

Lignin The fragmentation of lignin through the cleavage of ethereal bonds may produce a wide variety of chemicals that have a complex structure (Figure 13.3). 

The pioneer work in this field was carried out on polystyrene-supported acid catalysts [161]. Thereafter, several works on the use of sulfonic, strong acidic cation exchangers as acid catalysts were reported for alkylation, hydration, etherification, esterification, cleavage of ether bonds, dehydration, and aldol condensation [162,168-171], Besides, industrial applications of these materials were evaluated with reactions related to the chemistry of alkenes, that is, alkylation, isomerization, oligomerization, and acylation. [163,169], Also, Nation, an acid resin which has an acid strength equivalent to concentrated sulfuric acid, can be applied as an acid catalyst. It is used for the alkylation of aromatics with olefins in the liquid or gas phases and other reactions however, due to its low surface area, the Nation resin has relatively low catalytic activity in gas-phase reactions or liquid-phase processes where a nonpolar reactant or solvent is employed [166],... 

Lundquist K, Lundgren R (1972) Acid degradation of lignin VII The cleavage of ether bonds Acta Chem Scand 26 2005-2023... 

Selective cleavage of ether bonds is useful to determine the contribution of carbon-carbon bonds for polymer lignin. Pivaloyl iodide [90] is known to cleave a-ether bonds selectively and trimethylsilyl iodide [91,92] can cleave a- and P-ether bonds quite effectively under the proper reaction conditions. Because of the very small amount of sample required, pyrolysis GC-MS may be applied for the analysis of a specific morphologi region of a cell wall. 

There are cases when a substrate is not used for growth, but is metabolized in the presence of a second substrate that is used to support microorganism reproduction. This type of transformation is called cometabolism. Cometabolic conversions that apparently involve a single enzyme include hydroxylations, oxidations, denitrations, deaminations, hydrolyses, acylations, and cleavages of ether bonds. Many of these conversions are complex and involve several enzymes. This may be explained by the existence of enzymes that perform a single type of reaction, but which act on a series of closely related molecules. 

The reductive alkylation proceeds by the addition of electrons to the aromatic nuclei to form the corresponding anions followed by C-alkylatlon. Cleavage of ether bonds results In phenolate anions and subsequent 0-alkylatlon of the anions solubilizes coal. Coal has also been solubllzed by a grafting... 

A polymeric triphenylphosphine dibromide was synthesized by Michels and Heitz (1975) and was used for the cleavage of ether bonds. 

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