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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Aznhmonglor on March 09, 2009, 07:16:21 PM

Title: Terminal Alkenes
Post by: Aznhmonglor on March 09, 2009, 07:16:21 PM

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I know what happens in B and C but I am stuck on A. What does the NaOH do to the Br?

Title: Re: Terminal Alkenes
Post by: azmanam on March 09, 2009, 07:29:54 PM

Same thing it does in B... just a different regioisomer.  There's a rule governing these eliminations...

Title: Re: Terminal Alkenes
Post by: Aznhmonglor on March 09, 2009, 07:37:00 PM

Okay so I did what I did to B on A and got this but was not correct.

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv470%2Fazn_hmong_lor%2Funtitled-3.jpg&hash=30eb90762315bfe8dedb28fb1f5e093136a9a0c5)

What did I do wrong? Was it because the NaOH cannot attack the carbon center which already has 4 bonds?

Title: Re: Terminal Alkenes
Post by: azmanam on March 09, 2009, 07:42:38 PM

oh.  then you got B wrong.  They're all eliminations.

Title: Re: Terminal Alkenes
Post by: Aznhmonglor on March 09, 2009, 07:45:39 PM

No I got B right. This is what B came out to being.

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv470%2Fazn_hmong_lor%2Funtitled-4.jpg&hash=52e9f755f611b439bfbd2aa94259dab22f8703d0)

Title: Re: Terminal Alkenes
Post by: azmanam on March 09, 2009, 07:47:47 PM

then none of them give you the target product.  to get the target product, you must do an elimination.

Title: Re: Terminal Alkenes
Post by: Aznhmonglor on March 09, 2009, 07:50:36 PM

I am so sorry azman I forgot to include this part.

"Synthesizing terminal alkenes by the following routes is problematic because the terminal alkene shown in the box is only a minor product if formed at all."

So that does mean that all the reactions will not give me the target product thats what the professor wanted us to know. So for A would it eliminate the Br and form a double bond like so?

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv470%2Fazn_hmong_lor%2Funtitled-5.jpg&hash=ce0b3d04086ad18bfd13bdb25b129b705f5479cb)

Title: Re: Terminal Alkenes
Post by: azmanam on March 09, 2009, 08:00:56 PM

imho, yes.  You miiiiight get some E1, but that will be the major pdt of A.

Title: Re: Terminal Alkenes
Post by: azmanam on March 09, 2009, 08:01:23 PM

start here:

http://www.cem.msu.edu/~reusch/VirtTxtJml/alhalrx3.htm#hal9

Title: Re: Terminal Alkenes
Post by: Aznhmonglor on March 09, 2009, 08:03:05 PM

Thanks much. I was correct.