Counting Isomers (1 Viewer)

[facebooknerd123]

For example, 1-bromohexane, would I just count how many times the bromine can be placed on one side (in this case, this gives us 6)
and not count the other side as you could just rotate it? so the isomers is 6? Or is it just 3 because you can flip it?
Also, could the bromine atom be on either ends of the chain? Or do hydrogen atoms HAVE to occupy them?

 

[rand_althor]

There are 6 carbon atoms. The Br could be on any of the 6, but some of these are identical, so we don't count them. If the Br was on the first carbon atom, there are 3 places where you could position it when drawing, but these 3 are essentially the same as they all show 1-bromohexane. Similarly, if the Br was on the second carbon atom, there are 2 places where it can be drawn, but these 2 are the same as they show 2-bromohexane. Finally, following the same logic for the third carbon atom, there is essentially only one place where the Br atom can be drawn to depict 3-bromohexane. In total, there are 3 isomers. You don't consider the fourth carbon atom, as this would be the third carbon atom from the other side, and the lower number gets preference.

The bromine atom can occupy the ends of a chain.

 

[someth1ng]

There's even more isomers if you rearrange the carbon atoms such as 2-bromo-3-methylpentane. However, of you want only isomers of the 6 carbon straight chain, it would be 3.

 

[facebooknerd123]

so, I shouldn't examine it based on what it looks like? I should just name it to confirm if it would have the same name?
Also, so any other atom can also occupy the end positions? Not just hydrogen?

 

[someth1ng]

Don't really know what you mean, if the structures are different if you try to superimpose them, then they are isomers (assume same chemical structure).

 

[rand_althor]

so, I shouldn't examine it based on what it looks like? I should just name it to confirm if it would have the same name?
Also, so any other atom can also occupy the end positions? Not just hydrogen?

Draw the structure and you should see if some are the same. You don't have to name it, unless that helps you.