SCH4U
(Isomerism)
Handout
Isomerism
Isomerism is the phenomenon whereby certain compounds, with the same molecular formula, exist in
different forms owing to their different organisations of atoms. The concept of isomerism illustrates the
fundamental importance of molecular structure and shape in organic chemistry.
Structural Isomers have different structural formulae because their atoms are linked together in
different ways
Example1:
Notice that the number of carbon atoms and hydrogen atoms are same in both molecules.
Example 2:
Stereoisomers have the same structure and bond order but their atoms and groups of atoms are
arranged differently in space. They have different spatial arrangements and their molecules are not
superimposable. There are two types:
Geometric Isomerism: involves a double bond, usually C=C, that does not allow free rotation about the
double bond (unlike a C-C single bond).
Example:
Optical isomerism: Involves an atom, usually carbon, bonded to four different atoms or groups of
atoms. They exist in pairs, in which one isomer is the mirror image of the other.
Answer the following questions
1. How many structural isomers does C5H12 have? Draw them.
2. Name them.
3. How many structural isomers does C7H16 have? Draw them.