Video Transcript
What type of isomerism is exhibited by the three compounds in the diagram?
This problem is asking us to examine the diagram and determine the type of isomer illustrated by the three compounds. First of all, isomers are molecules with the same molecular formula but a different arrangement of atoms in space. Let’s start by confirming that the three compounds have the same molecular formula. By using these pink circles to represent the location of the carbon atoms in the molecules, we can more easily see that all three molecules contain seven carbon atoms. Each line segment in the formulas represents a single covalent bond between atoms.
In these formulas, the hydrogen atoms that are bonded to the carbon atoms are not shown. But if we drew the displayed formulas for each molecule, we’d see that there are a total of 16 hydrogen atoms present in each molecule. Finally, each molecule also contains one oxygen atom. So each molecule contains the same number of atoms of each element. In total, each molecule contains seven carbon atoms, 16 hydrogen atoms, and one oxygen atom. Therefore, all three molecules have the same molecular formula, which is C7H16O.
Now, when comparing the three molecules, we notice that they all contain a hydroxy or OH group, which is the functional group of an alcohol. We also notice that the hydroxy group is located at a different position on the carbon chain in each molecule. In the first compound, the hydroxy group is located on carbon number one. In the second compound, it is located on carbon number two. And in the third compound, it is located on carbon number three. We can therefore classify these isomers as structural isomers because they have the same molecular formula but differ by how their atoms are connected.
There are several different types of structural isomerism possible. If the isomers have the same functional groups but these functional groups are found at different positions on the carbon chain, then the isomers are classified as positional isomers. In conclusion, since the alcohol functional group is located on a different carbon atom in each compound and each compound has the same molecular formula, the type of isomerism exhibited by the three compounds is positional isomerism.
