Numbering

Moderators: Chem_Mod, Chem_Admin

Jasmine Alcantara 3G
Posts: 18
Joined: Wed Sep 21, 2016 2:58 pm

Numbering

Postby Jasmine Alcantara 3G » Wed Mar 08, 2017 6:29 pm

For numbering multiple constituents, do we always make the first constituent the lowest possible number even when sacrificing a smaller overall number total? Or are we going for the lowest sum total?

Mannat Sukhija 1E
Posts: 23
Joined: Fri Jul 22, 2016 3:00 am

Re: Numbering

Postby Mannat Sukhija 1E » Wed Mar 08, 2017 6:51 pm

I believe you want to aim for the first number to be as small as possible opposed to a smaller sum of substituent numbers.

Janice Kim 3I
Posts: 33
Joined: Wed Sep 21, 2016 2:56 pm

Re: Numbering

Postby Janice Kim 3I » Wed Mar 08, 2017 6:51 pm

Hey! When numbering multiple constituents, always aim for the lowest sum total. If there is equal numbering between constituents (for example 2,3 or 3,2) then apply the lowest number to the first alphabetical constituent, not including the prefixes.

DBaquero
Posts: 13
Joined: Wed Sep 21, 2016 2:59 pm
Been upvoted: 1 time

Re: Numbering

Postby DBaquero » Sun Mar 12, 2017 9:03 pm

I believe Professor Lavelle told us to aim for the lowest first number. If the first number would be the same either way then aim for the lowest second number as well (and so on).

andrea_Disc3D
Posts: 10
Joined: Wed Sep 21, 2016 2:55 pm

Re: Numbering

Postby andrea_Disc3D » Sun Mar 12, 2017 10:01 pm

I heard someone say that you should also number a molecule so that you have the most substituents. I was wondering if anyone knew whether this was true or not?

ribal_daniel_3H
Posts: 13
Joined: Wed Sep 21, 2016 2:58 pm

Re: Numbering

Postby ribal_daniel_3H » Mon Mar 13, 2017 11:37 am

The way I see it is that we should strive to have the longest carbon chain. Also you want the first number to be the lowest I think. So if you have a 2 or 4-methyl and a 2 or 4-ethyl on a pentane, you would write 2-ethyl-4methylpentane.

angelicapayne
Posts: 10
Joined: Wed Sep 21, 2016 2:58 pm
Been upvoted: 1 time

Re: Numbering

Postby angelicapayne » Mon Mar 13, 2017 3:20 pm

My TA mentioned the sum rule works only in some cases so it is not always a reliable way to determine numbering


Return to “*Alkanes”

Who is online

Users browsing this forum: No registered users and 3 guests