5 Steps to a 5 AP Chemistry

274  Step 4. Review the Knowledge You Need to Score High

molecular masses in the millions. They are large, complex molecules, but most are com-

posed of repeating units called monomers. Figure 18.4 shows two macromolecules, cellu-

lose and nylon, and indicates their repeating units.

Macromolecules are found in nature. Cellulose, wool, starch, and DNA are but a few

of the macromolecules that occur naturally. Carbon’s ability to form these large, complex

molecules is necessary to provide the diversity of compounds needed to make up a tree or

a human being. But many of the useful macromolecules that we use every day are created

in the lab and industrial complex by chemists. Nylon, rayon, polyethylene, and polyvinyl

chloride are all synthetic macromolecules. They differ by which repeating units

(monomers) are joined together in the polymerization process. Our society has grown to

depend on these plastics, these synthetic fabrics. The complexity of carbon compounds is

reflected in the complexity of our modern society.

Experimental

Experiment 22 in the Experimental chapter applies the concepts of organic chemistry in a

synthesis situation.

Common Mistakes to Avoid

1. When writing organic formulas, make sure that every carbon has four bonds.


2. When naming alkanes, make sure to number the carbon chain so the sum of all loca-
   tion numbers is as small as possible.


3. When naming branched alkanes, be sure to consider the branches when finding the longest
   carbon chain. The longest chain isn’t always the one in which the carbon atoms all lie in a
   horizontal line.


4. In naming identical substituents on the longest carbon chain, be sure to use repeating
   location numbers, separated by commas (2,2-dimethyl).


5. Be sure that every carbon has four bonds!

H

H

HO OH

CH 2 OH

H

H

O

O

H

H

H

HO OH

CH 2 OH

H

H

O

O

H

H

H

HO OH

CH 2 OH

H H

O

O

H

H

H

HO OH

CH 2 OH

H H

O

O

Repeating unit H

Cellulose

HO C

O

CNH NH H

n

(CH 2 ) 4

O

(CH 2 ) 6

Nylon

Figure 18.4 Two macromolecules.

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