Sugars monomers from

Monosaccharide Simple sugars (monomers) from which more complex carbohydrates are constructed. 

The reliance of fossil fuels has been challenged by lower cost and renewable sources that are more environmentally friendly. The traditional chemical plant has met serious competition from green plants. Many monomers are now made via fermentation, using low-cost sugars as feedstock. Some of the commodity monomers are under siege by chemicals extracted from biomass. Monomer production has been expanded to include many more monomers from nature. 

Cellulose and starch are macromolecules with empirical formulas that resemble hydrated carbon, CX (H2 0)y, where x and y are integers. The monomers from which these macromolecules are consfructed are sugars such as glucose and fructose. These monomers and macromolecules are the carbohydrates. Structurally, carbohydrates are very different from simple combinations of carbon and water. Even the smallest carbohydrates contain carbon chains with hydrogen atoms, OH groups, and occasional ether linkages. 

The complete elimination of functional groups is often an undesirable side reaction in organic synthesis, but on the other hand it is a possibility for the recycling of environmentally harmful compounds, for example phenols and haloarenes such as polychlorinated dibenzodioxins (PCDDs or dioxins ). For example, aryl chlorides can be effectively dechlorinated with Pd(0) NPs in tetra-butylammonium salts with almost quantitative conversions also after 19 runs (entry H, Table 1.4) [96]. On the other hand, a C-0 bond cleavage reaction also seems suitable for the fragmentation of sugar-based biomass such as cellulose or cello-biose in that way, sugar monomers and bioalcohol can be derived from renewable resources (entry F, Table 1.4) [164]. 

Polymers are large molecules formed by the repetitive bonding together of many smaller molecules, called monomers. As we ll see in the next chapter, biological polymers occur throughout nature. Cellulose and starch are polymers built from small sugar monomers, proteins are polymers built from amino acid monomers, and nucleic acids are polymers built from nucleotide monomers. The basic idea is the same, but synthetic polymers are much less complex than biopolymers because the starting monomer units are usually smaller and simpler. 

There is an anomeric carbon, resulting from the equilibrium between the acychc form and the four cyclic forms of a sugar monomer in solution. These cychc forms are comprised of a five-membered furanose ring and the generally more abundant six-membered pyranose ring. Mutorotation around the anomeric centre converts the a-form into the P-form. 

The molecular mass of a oligosaccharide can be calculated from residue masses of individual sugar units in the molecule from M = 18 + S (Residue masses of monomeric units). Residue masses of some important monomeric units are given in Table 20.1. Relevant sugar monomer stmctures are shown in Figure 20.1. 

A variety of vinyl sugar monomers have been prepared and polymerized.154 Many of the syntheses involve various protecting groups. Probably, the most practical and direct syntheses are those involving enzymatic formation of acrylates (as described in Chapter 9). This has been used to produce sucrose acrylate, as well as a monomer (12.29) made from a-methylgalactose and vinyl acrylate. 

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