Polymerization oxidative coupling reaction

Polymerization, or conjugation, is the process in which toxic organic molecules undergo microbially mediated transformation by oxidative coupling reactions. In this case, a contaminant or its intermediate product(s) combines with itself or other organic molecules (e.g., xenobiotic residues, naturally occurring compounds) to form larger molecular polymers that can be incorporated in subsurface humic substances. 

As shown in recent investigations, catalyzed oxidative coupling of organic molecules provides a new and general route to a variety of hitherto only difficulty accessible polymer systems. While the literature on oxidative coupling reactions in polymer synthesis is already rather extensive, by further investigations of this reaction concept, particularly studies of the catalysis involved, oxidative coupling promises to rival conventional condensation and addition polymerization in importance. 

A. Coupling reaction using ferric chloride (FeCl ) as oxidant 1, The polymerization from homo-monomer Compound 16 isolated from Vitis amurensis showed strong biological activity [7, 65] and its biomimetic synthesis was achieved as shown in Fig. (7). Oxidative coupling reaction of 1 with FeCU as oxidant produced an intermediate, ( )- -viniferin (107), by silica gel column chromatography. After acetylation, it was dehydrogenated by treatment with 2,3-dichloro-5,6- dicyano-1, 4-benzoquinone (DDQ) to afford an intermediate(108) and the desired compound 16 in 20% yield [7]. 

Oxidative coupling reaction of bi-thiophene in presence of ferric chloride using AICI3, CUCI3 and organic solvents Plasma polymerization from 3-methyl thiophene or thiophene... 

Linked Eg Clusters The formation ofstable radicals [ 9 ] also opens the possibility of cluster dimerization and - through further oxidation - the formation of polymeric chains with exo-bonds between the clusters. Hitherto, such oxidative coupling reactions have been reported exclusively for Gcg clusters (Figure 3.4). In... 

Aluminum chloride reacts with an arene to give the arene radical-cation, which further follows the generally accepted oxidative coupling reaction mechanism, by an influence of copper(II) chloride as an oxidant to finally give a well defined polymeric product [65],... 

Another proposed mechanism of the polymerization is a two-electron transfer mechanism, which involvs phenolate-bridged dinuclear copper(II) complex as starting species. The complex generated phenoxonium cations and phenolate anion through a double one-electron transfer from a phenolate to both copper centres (step v) and form the quinone-ketal intermediate via nucleophilic attack (step vi). This reaction pathway is supported by theoretical calculations of atomic charges of monomeric and dimeric species of 2,6-DMP where phenoxonium cations are proposed as key intermediates. Ab Initio calculations on 2,6-DMP and 4-(2,6-Dimethylphenoxy)-2,6-dimethylphenol provided evidence of the phenoxonium cation in the copper-catalyzed oxidative coupling reaction which proposed that the selective C-O coupling was achieved via the nucleophilic attack of a phenolate on the para-carbon of a phenoxonium cation (25). Based on the experimental evidence currently reported, both... 

The resveratrol oligomers appear to be formed via oxidative coupling reactions, which are enzymatically controlled to yield optically active products. Many polyphenols of the stilbene type (e.g. resveratrol) are sensitive to oxidation in air and polymerization. The dark-colored products thus formed should be structural-... 

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