Numbering for Cycloalkenes

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Daniel_Sands3L
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Joined: Fri Sep 25, 2015 3:00 am

Numbering for Cycloalkenes

Postby Daniel_Sands3L » Fri Feb 26, 2016 12:27 pm

How does the numbering for cycloalkenes work? Do you have the lowest number next to the double bonds or largest substituent?

Andre Tsivis 1K
Posts: 16
Joined: Fri Sep 25, 2015 3:00 am

Re: Numbering for Cycloalkenes

Postby Andre Tsivis 1K » Fri Feb 26, 2016 1:16 pm

Double bonds hold priority. The best way to name cycloalkenes is to have the double bonds have priority over the substituents. However, the double bond with the most substituants directly in front of it should get the lower number, hence making the most substituent groups have lower numbers. Of course most organic rings will be unique, but for he cycloalkenes, look for the double bonds, find the nearby substituents for each, then pick a direction (clockwise vs counterclockwise) that will include the most substituents giving a relatively lower number for each. Number each on the ring, line up the substituents alphabetically and number accordingly. Hope this helps!

Andre Tsivis 1K
Posts: 16
Joined: Fri Sep 25, 2015 3:00 am

Re: Numbering for Cycloalkenes

Postby Andre Tsivis 1K » Fri Feb 26, 2016 1:21 pm

Also, the length of the substituent doesn't matter, only the placement does. A methyl group holds the same numbering priority as a larger substituting such as an isopropyl or tert-pentyl group. But as always, this ordering still has a lower priority than making the double bonds as low of a number as possible. Again, hope this helps!


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