Video Transcript
1-Chlorohexane, 2-chlorohexane, and 3-chlorohexane have the same molecular formula of C6H13Cl. What type of isomerism is exhibited between these three compounds?
The question asks about three compounds: 1-chlorohexane, 2-chlorohexane, and 3-chlorohexane. We are told that they have the same molecular formula, and we are asked what type of isomerism is exhibited. Isomers are molecules with the same molecular formula but a different arrangement of the atoms in space. There are two broad categories of isomers: structural isomers and stereoisomers. Structural isomers are further divided into chain isomers, positional isomers, and functional isomers. And stereoisomers also have two subgroupings: geometric and optical isomers.
Structural isomers have the same molecular formula but differ by how atoms are connected. We are told that our three compounds have the same molecular formula. And we can see that they each have a different carbon number to which the chloro group is attached. So we know we are dealing with structural isomers. Stereoisomers do not have to do with a structure or arrangement of molecules or what atoms are bonded together, but rather the spatial arrangement of parts of a molecule in three dimensions.
So what are chain, positional, and functional isomers? Let’s turn this around to have a look. Chain isomers are molecules that have the same molecular formula but a different arrangement of the carbon chain. Positional isomers have the same molecular formula and the same functional group. However, the functional group or groups have different positions on the carbon chain. And functional isomers are molecules with the same molecular formula but a different functional group or groups.
To identify which type of isomerism exists between the three given compounds, we first need to know their structures. All three isomers are based on hexane chains, or chains of six carbon atoms. However, in isomer one, we have a chlorine atom on carbon number one. So, for 1-chlorohexane, we can erase one of the hydrogen atoms on carbon number one and replace it with a chlorine atom. In the second isomer, there is a chlorine atom on carbon number two. So, in the structure for 2-chlorohexane, we can erase one of the hydrogen atoms on carbon number two and replace it with a chlorine atom. Similarly, for the third isomer, there is a chlorine atom on carbon number three. In the structure of 3-chlorohexane, we can erase a hydrogen atom on carbon number three and again replace it with a chlorine atom.
Looking at the three structures, we can see that they are all identical except for the position of the chlorine functional group. So we must be looking at positional isomers. Finally, what type of isomerism is exhibited between these three compounds? The answer is positional isomerism.
