Introduction

As knowledge of chemistry slowly grew in the 1700s, mysterious differences were noted between compounds obtained from living sources and those obtained from minerals. It was found, for instance, that chemicals from living sources were often liquids or low-melting solids, while chemicals from mineral sources were usually high-melting solids. Furthermore, chemicals from living sources were generally more difficult to purify and work with than those from minerals. To express these differences, the term organic chemistry was introduced to mean the study of compounds from living organisms, while inorganic chemistry was used to refer to the study of compounds from minerals.

Today we know that there are no fundamental differences between organic and inorganic compounds: The same scientific principles are applicable to both. The only common characteristic of compounds from living sources is that they contain the element carbon. Thus, organic chemistry is now defined as the study of carbon compounds.

Why is carbon special? The answer derives from its position in the periodic table. As a group 4A nonmetal, carbon atoms have the unique ability to form four strong covalent bonds. Furthermore, carbon atoms can bond together, forming long chains and rings. Of all the elements, only carbon is able to form such an immense array of compounds, from methane with one carbon atom to DNA with billions of carbons.

In this and the next five chapters, we'll look at the chemistry of organic compounds, beginning with answers to the following questions:

1. What are functional groups, and how are they used to classify organic molecules?
   The goal: Be able to classify organic molecules into families by functional group.
2. What are isomers?
   The goal: Be able to recognize and draw constitutional isomers.
3. How are organic molecules drawn?
   The goal: Be able to convert between structural formulas and condensed or line structures.
4. What are alkanes and cycloalkanes, and how are they named?
   The goal: Be able to name an alkane or cycloalkane from its structure, or write the structure, given the name.
5. What are the general properties and chemical reactions of alkanes?
   The goal: Be able to describe the physical properties of alkanes and the products formed in the combustion and halogenation reactions of alkanes.