In the previous lesson, you learned that isomers are compounds that have the same molecular formula, but different structures; and the members in a group of structural isomers have different properties. For example, ethyl butyrate and hexanoic acid both have the same molecular formula C6H12O2.
However, hexanoic acid smells like sweaty gym socks while ethyl butyrate smells like fresh pineapple! The difference in their properties is due to how the atoms are arranged.
In this lesson you will learn how chemists group organic compounds into specific categories based on structure. Because the molecules within each category have a similar structure, they will also have similar properties.
Question
Consider these two structural formulas for two isomers with the molecular formula C6H12O2.
A molecule consisting of a chain of carbon atoms. A carbon atom at the end of the chain is double bonded to an oxygen atom and single bonded to a hydroxyl (OH-) group.
Hexanoic acid, C6H12O2 (stinky sock smell)
A molecule consisting of a chain of carbon atoms. A carbon atom in the middle of the carbon chain is double bonded to an oxygen atom. That carbon atom is also single bonded to an oxygen atom, which is single bonded to a carbon atom, and that carbon atom is bonded to another carbon atom.
Ethyl butyrate, C6H12O2 (pineapple smell)
Both of these molecules have a 6-carbon chain, and both include oxygen atoms as part of their structure. But how are they different?
These compounds include two oxygen atoms as part of their structure. The arrangement of these oxygens, however, is different. In ethyl butyrate, both oxygen atoms are in the middle of the carbon chain. In hexanoic acid, both oxygen atoms are at one end of the carbon chain.
