Naming hydrocarbons (1 Viewer)

[hs17]

For halogenated alkanes, say there is a chloro and fluoro on different positions of the chain...which one gets priority in numbering?

 

[jazz519]

The priority isn't based on the type of halogen atom. It is about the total sum of the numbers used in the naming being the lowest

So for example in naming this:


We would either name it as:
1,1-dichloro-3-fluoropropane or 3,3-dichloro-1-fluoropropane

The Cl comes first in the name as it alphabetically before fluoro, that is the only thing the type of halogen influences.

Other than that we just look at the total sum for haloalkanes. We can see in the first name that it has a sum of 1+1+3=5 and the second name has sum of 3+3+1=7.

Therefore, we choose the first name

 

[hs17]

Thank you,
I read somewhere that it is based on the electronegativity of the halogen but that rule wasn't working with any past questions so I was really confused. Thank you for clearing that up!