October 13, 2015

Homework Help: OChem Nomenclature

Posted by Lacey on Wednesday, June 13, 2007 at 11:30pm.

Here is a compound that I am trying to name...
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I came up with 3-methylheptene, but the answer says 2-ethyl-1-hexene. Can someone please explain why I'm wrong? Thanks

that showed up wrong - the methyl with the double bond should be on that lone carbon in the third spot...


Yeah, that's what it should look like and I'm trying to name it - I came up with 3-methylheptene but the real answer is supposed to be 2-ethyl-1-hexene and I don't understand why...

OK. If that is the correct structure (drawing structures on this board is TOUGH), you want the longest chain containing the double bond. Start counting at the CH2 group on top, go down and to the right. That gives 6 carbons which will be hexene. The double bond is on the #1 carbon and there is a CH3-CH2- group (ethyl group) on the #2 carbon. So it is 2-ethyl-1-hexene.

Ok, that makes so much more sense!!! It was driving me crazy! :) Thanks a lot!

Agreed on the name.

You could also show it as


which makes the name more obvious.

Another way to draw the structure without the spacing problem (I think) is to do the following:
I'll leave this up if it looks ok.

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