Multiple possible names

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Ethan_Kato_1D
Posts: 25
Joined: Fri Jul 15, 2016 3:00 am

Multiple possible names

Postby Ethan_Kato_1D » Tue Mar 07, 2017 6:00 pm

When you are naming a cycloalkane, and you find multiple names possible, how do you determine which is best? Do you pick the name with overall lower numbers? Do you compare each number consecutively? Do you pick the name with the lowest first number (because it is based alphabetically)?

Why does the book/notes say to give the first substituent the lowest number, even when in some examples that is not followed?

Karan Ishii 3E
Posts: 21
Joined: Wed Sep 21, 2016 3:00 pm

Re: Multiple possible names

Postby Karan Ishii 3E » Tue Mar 07, 2017 6:46 pm

The one with the smallest overall number.

ex) 4-bromo-1-methoxy-2-nitrobenzene is correct
1-bromo-4-methoxy-3-nitrobenze is incorrect

Johnson Thai 1L
Posts: 19
Joined: Wed Sep 21, 2016 2:59 pm

Re: Multiple possible names

Postby Johnson Thai 1L » Thu Mar 09, 2017 2:30 pm

I think it depends on the number of substituents. When there are just two substituents, it would make sense to assign the smaller number to the substituent that would be named first alphabetically, and then the second substituent would get the next number. However, when you have three or more substituents, if you use that rule, then the overall numbering might be a lot bigger. In that case, you would use the smallest overall numbering. I hope that made some sense.


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