Together to form a large molecule

Another important reaction involving certain unsaturated hydrocarbons is polymerization, a process in which many small molecules are joined together to form a large molecule. Polymerization will be discussed in Section 22.5. 

In initiation, a chemical creates an active free radical. This free radical is quite unstable but very reactive because of unpaired electrons in the molecule. This is a monomer with an unpaired electron. Once this is formed, the addition begins as the free radical reacts with another monomer radical. This reaction results in the formation of another monomer and the chain reaction is started as the addition continues with subsequent monomers. Within a fraction of a second, addition of tens of millions of monomers takes place. Finally, when two of the free radical ends encounter each other and bond together to form a large molecule, the termination occurs as the unpaired electrons are joined. 

Polymerization a process in which small molecules called monomers are joined together to form a large molecule. 

In addition polymerisation, the molecules of the same or different monomers add together to form a large polymer molecule. Condensation polymerisation is a process in which two or more bi-functional molecules undergo a series of condensation reactions with the elimination of some simple molecules and leading to the formation of polymers. 

A key related property of carbohydrates in their role as mediators of cellular interactions is the tremendous structural diversity possible within this class of molecules. Carbohydrates are built from monosaccharides, small molecules that typically contain from three to nine carbon atoms and vary in size and in the stereochemical configuration at one or more carbon centers. These monosaccharides may be linked together to form a large variety of oligosaccharide structures. The unraveling of these oligosaccharide structures, the discovery of their placement at specific sites within proteins, and the determination of their function are tremendous challenges in the field of proteomics. 

Cellulose consists of several thousand o-glucose units linked by l- 4-/3-glyco-side bonds like those in cellobiose. Different cellulose molecules then interact to form a large aggregate structure held together by hydrogen bonds. 

Ethene or ethylene is the most important organic chemical used in commercial applications. Annual production of ethylene in the United States was over twenty-five million tons in the year 2000. Propylene is also used in large quantities with an annual production of over thirteen million tons. Alkenes such as ethylene and propylene have the ability to undergo addition polymerization. In this process, multiple addition reactions take place and many molecules link together to form a polymer. A polymer is a long chain of repeating units called monomers. For example, the addition of two ethylene molecules can be represented as... 

A large fraction of the chemical industry worldwide is devoted to polymer manufacture, which is very important in the area of hazardous wastes, as a source of environmental pollutants, in toxicology, and in the manufacture of materials used to alleviate environmental and waste problems. Synthetic polymers are produced when small molecules called monomers bond together to form a much smaller number of very large molecules. Many natural products are polymers for example, cellulose in wood, paper, and many other materials is a polymer of the sugar glucose. Synthetic polymers form the basis of many industries, such as rubber, plastics, and textiles manufacture. 

How are such intermediates formed from the parental duplexes and resolved to form products Many details for this process are now available, based largely on the results of studies of Cre recombinase from bacteriophage PI. This mechanism begins with the recombinase binding to the DNA substrates (Figure 27 39). Four molecules of the enzyme and their associated DNA molecules come together to form a. recombination synapse. The reaction begins with the... 

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