Explain why a change in the position of a substituent group (i. e., which carbon the group is attached to) can, but does not always, result in a different compound

Changing the position of the substituents in an organic molecule will often result in a different chemical compound. If the structure of the molecule changes but it still has the same molecular formula, i.e., the same number of each atom, then this is called a structural isomer. However, it is possible to change the position of a substituent and the structure of the molecule remain unchanged. This would most likely occur in symmetric molecules.

CH₃ - CH₂ - CH₂ - CH₂ - OH    1-butanol

CH₃ - CH₂ - CH - CH₃    2 - butanol
                    |
                   OH

Looking at the two structures above, the position of the -OH was moved from the 1-carbon to the 2-carbon, resulting in two different molecules. These are structural isomers. However, we can also move the -OH group without changing the molecule.

CH₃ - CH₂ - CH - CH₃     2-butanol
                    |
                   OH
CH₃ - CH - CH₂ - CH₃     2-butanol
           |
          OH
In the above structure, it appears that the -OH group was moved from the 2-carbon to the 3-carbon, but since this molecule is symmetrical, the 2- and 3-carbons are equivalent. Therefore, swapping substituents has no effect on the structure of the molecule and these are equivalent.

Ithink it’s one of those things that you put the object on