You probably recognize this image as the great seal of the United States. The motto on the seal, E pluribus unum , is Latin for “out of many, one.” It refers to the formation of one country out of many states. Large carbon compounds could have the same motto. Can you guess why? In this lesson, you’ll find out.
Out of Many, One
Carbon has a unique ability to form covalent bonds with many other atoms. It can bond with other carbon atoms as well as with atoms of other elements. Because of this ability, carbon often forms polymers. A polymer is a large molecule that is made out of many smaller molecules that are joined together by covalent bonds. The smaller, repeating molecules are called monomers . (The prefix mono - means “one” and the prefix poly - means “many.”) Polymers may consist of just one type of monomer or of more than one type. Polymers are similar to the strings of beads pictured in the Figure below . Like beads on a string, monomers in a polymer may be all the same or different from one another.
Natural Carbon Polymers
Many polymers of carbon occur naturally. Two examples are rubber and cellulose.
- Rubber is a natural polymer of the monomer named isoprene (C 5 H 8 ). This polymer comes from rubber trees, which grow in tropical areas. Structural formulas for rubber and isoprene are shown in the Figure below . Note that just a small section of the rubber polymer is represented by the structural formula.
- Cellulose is a natural polymer of the monomer named glucose (C 6 H 12 O 6 ). This polymer makes up the cell walls of plants and is the most common compound in living things. Structural formulas for cellulose and glucose are also shown in the Figure below ). As you can see from the structural formula for cellulose, when two glucose monomers bond together, a molecule of water (H 2 O) is released.
Q: How are the glucose molecules arranged in the cellulose polymer?
A: The glucose molecules alternate between right-side up and upside down.
Synthetic Carbon Polymers
Synthetic carbon polymers are produced in labs or factories. Plastics are common examples of synthetic carbon polymers. You are probably familiar with the plastic called polyethylene. All of the plastic items pictured in the Figure below are made of polyethylene. It consists of repeating monomers of ethylene(C 2 H 4 ). Structural formulas for ethylene and polyethylene are also shown in the Figure below . To learn more about synthetic carbon polymers and how they form, go to this URL: http://www.youtube.com/watch?v=7nCfbZwGWK8
- Carbon has a unique ability to form many covalent bonds, so it often forms polymers. A polymer is a large molecule that is made up of many smaller, repeating molecules, called monomers, which are joined together by covalent bonds.
- Natural polymers include rubber and cellulose. Synthetic polymers include plastics such as polyethylene.
- monomer : Small molecule that forms covalent bonds with other small molecules to produce a large molecule called a polymer.
- polymer : Large molecule that consists of many smaller molecules, called monomers, joined together by covalent bonds.
Watch the video about polymers at the following URL, and then answer the questions below.
- Define the two parts of the word polymer, and give a literal definition of polymer.
- Describe two properties of polymers that depend on their long-chain structure.
- Name three items that consist of or contain polymers.
- Define polymer and monomer.
- Describe an example of a natural carbon polymer.
- What are some uses of synthetic carbon polymers?