## Order of writing halogens

Betty Tesfaye 2G
Posts: 11
Joined: Fri Sep 25, 2015 3:00 am

### Order of writing halogens

If you have more than one halogen attached to a carbon ring or chain how do you know which to give the lowest number and then how would you order that in the name?

Pauline Tran 2G
Posts: 20
Joined: Fri Sep 25, 2015 3:00 am

### Re: Order of writing halogens

You would first figure out all possible sets of numbers for the two halogens and then assign the lowest set of numbers to them. For example, in 5-chloro-2-iodoheptane, 5 and 2 is the lowest set of numbers, as the other possible set would be 3 and 6.

angelicapayne
Posts: 10
Joined: Wed Sep 21, 2016 2:58 pm
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### Re: Order of writing halogens

You would start numbering at the halogen that comes alphabetically first. For example if you had 1-bromo-3-chlorocyclohexane, because "b" comes before "c", you start numbering at the bromo and then go in the direction that gives the chloro the smallest number.

angelicapayne
Posts: 10
Joined: Wed Sep 21, 2016 2:58 pm
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### Re: Order of writing halogens

angelicapayne wrote:You would start numbering at the halogen that comes alphabetically first. For example if you had 1-bromo-3-chlorocyclohexane, because "b" comes before "c", you start numbering at the bromo and then go in the direction that gives the chloro the smallest number.

http://www.chemsink.com/compound/22760233/ here is a picture of the molecule