Dimeric alcohol

Typical specifications for commercially available amyl alcohols (104) are given in Table 4. The impurities typically present are other monomeric alcohols, dimeric alcohols, acetals, and several miscellaneous substances. The alcohols are substantially free of suspended matter. 

Each PIR entry consists of Entry (entry ID), Title, Alternate names, Organism, Date, Accession (accession number), Reference, Function (description of protein function), Comment (e.g., enzyme specificity and reaction, etc.), Classification (superfamily), Keywords (e.g., dimer, alcohol metabolism, metalloprotein, etc.), Feature (lists of sequence positions for disulfide bonds, active site and binding site amino acid residues, etc.), Summary (number of amino acids and the molecular weight), and Sequence (in PIR format, Chapter 4). In addition, links to PDB, KEGG, BRENDA, WIT, alignments, and iProClass are provided. 

Besides the aforementioned Kolbe dimers, alcohols, esters or ethers can become the major products in the electrolysis of carboxylic acids. These results have suggested that in anodic decarboxylation the intermediate radicals were further oxidized to carbocations that yielded solvolysis and elimination prod-ucts. °2 This part of the anodic decarboxylation, which leads to carbenium ions, is frequently called nonKolbe electrolysis. Applications of the nonKolbe electrolysis to synthesis and to mechanistic investigation of carbocations are summarized in refs. 8,19,20 and 23. ... 

High performance in the synthesis of hydrolytically resistant polyurethanes was obtained by using in the polyesterification reaction, very hydrophobic fatty dimer acids and fatty dimer alcohols, products obtained from vegetable oils (see Chapter 12.5). The use of fatty dimeric acids and fatty dimeric alcohols (obtained by the hydrogenation of dimeric acids or dimeric esters) to build the polyester structure, creates an extremely high hydrophobic environment alongside a low concentration of labile ester bonds. 

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

By hydrogenation of these dimeric or trimeric acids the corresponding diols or triols are obtained. The dimer alcohol (Figure 17.12) has an hydroxyl number of 202-212 mg KOH/g and a molecular weight of 565 daltons and a viscosity of around 3,500 mPa-s at 25 °C [73, 74]. Trimer alcohols (Figure 17.13) have an hydroxyl number about 205 mg KOH/g and a viscosity of around 9,500 mPa-s at 25 °C [74]. 

It is considered that the polyurethanes based on oleochemical polyols, dimer acids and dimer alcohols, PTHF and PC-polyols lead to polyurethanes with excellent hydrolytic stability. Polycaprolactone (PCL) polyols and poly (butylene adipate) lead to polyurethanes with good hydrolytic stability, but use of poly (diethylene glycol adipate) give polyurethanes with poor hydrolytic resistance. 

Other Zinc Enzymes. Studies aimed at elucidating the mechanism of dimeric alcohol dehydrogenase enzymes have also been reported. Cobalt(n) can replace zinc(ii) at the two catalytic and non-catalytic sites in the liver enzyme, LADH. Reduction of pyridinealdehyde derivatives by the yeast enzyme has been examined. In acetonitrile solution, reduction by NADH analogues is catalysed by metal ions and mechanistic studies of the reaction have been carried out. Biomimetic studies of zinc-catalysed carbonyl reduction have also been reported. ... 

Tailor-made surface catalysts are required to improve the technical performance of known homogeneous processes as in alkene dimerization, alcohol homologation, and methanol carbonylation. 

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