Naming isopropyl substituent: Question 2.48

[Justin Le 2I]

I don't understand why the numbering wouldn't start at the isopropyl group and then go counterclockwise. The numbers would then be 1,2,and then 4. The answer starts at the OH and goes clockwise so the numbers are 1,2,5.

[Chem_Mod]

Hi Justin, because -OH is a suffix group (the molecule will take the ending "-ol" ), the -OH receives the lowest number possible, before we even consider the other groups.

[Justin Le 2I]

Thanks. Is isopropyl considered a functional group though?

[Chem_Mod]

No, isopropyl is an alkyl substituent, which can only take prefixes.

Prefix groups have the last priority when trying to assign low numbers (behind suffix group and also behind double/triple bonds).

[martha-1I]

Just thought I'd post this as a reminder of highest to lowest priority when it comes to numbering.
1) Functional groups (ex. carboxylic acid, alcohol, amine, aldehyde, ketone)
2) Double or triple bonds
3) Substituents

[Justin Le 2I]

Thank you!

[Chem_Mod]

yeah Martha is correct..you can follow that ordering for preferential numbering