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Naming isopropyl substituent: Question 2.48

Posted: Mon Mar 09, 2015 9:07 pm
by 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.

Re: Naming isopropyl substituent: Question 2.48

Posted: Mon Mar 09, 2015 9:14 pm
by 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.

Re: Naming isopropyl substituent: Question 2.48

Posted: Mon Mar 09, 2015 9:16 pm
by Justin Le 2I
Thanks. Is isopropyl considered a functional group though?

Re: Naming isopropyl substituent: Question 2.48

Posted: Mon Mar 09, 2015 9:19 pm
by 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).

Re: Naming isopropyl substituent: Question 2.48

Posted: Tue Mar 10, 2015 10:28 am
by 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

Re: Naming isopropyl substituent: Question 2.48

Posted: Wed Mar 11, 2015 10:00 pm
by Justin Le 2I
Thank you!

Re: Naming isopropyl substituent: Question 2.48

Posted: Wed Mar 11, 2015 11:30 pm
by Chem_Mod
yeah Martha is correct..you can follow that ordering for preferential numbering