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December 6, 2009 2:33 PM   Subscribe

Organic Chemistry filter: I just want to make sure I'm doing this right...

Yes, this is a homework problem. I admit it freely. But I put the time into it, and just want to make sure that I'm on the right track. I think I have it right. It seems pretty straightforward. If anyone can tell me if I am not thinking about it right or if I am on the right track, I would really appreciate it.

The problem: provide syntheses (should take 3 steps) to get from 1-butanol to hexene, from only the starting material and reagents or compounds with 2 carbons or less.

My answer:
Step 1: I used PBr3 to turn 1-butanol into 1-bromo butane + HoPBr2.
Step 2: I used an ethyne anion (via E2) to turn the 1-bromo butane
into 1-hexyne.
Step 3: I used 2 mol of H2 and a Pd catalyst to convert the
1-hexyne to hexene.

I hope I did this right! Can someone please let me know, and if not, tell me what direction to look in? Thank you!
posted by bolognius maximus to Science & Nature (4 answers total) 1 user marked this as a favorite
Two equivalents of hydrogen gas will bring it down to hexane. There are other techniques for a partial hydrogenation.
posted by d. z. wang at 4:12 PM on December 6, 2009

Oops, my bad. That was a typo. Thanks!
posted by bolognius maximus at 4:46 PM on December 6, 2009

You have it basically down, but for some nitpicks:

1. SN2, not E2. E2 is elimination.
2. You can't stop hydrogenation by limiting equivalents. You have to do it by reagent (using Lindlar's catalyst or Li/NH3).

posted by Dr.Enormous at 4:51 PM on December 6, 2009

Original problem should have said convert to hexane instead of hexene, my bad. Thanks for the suggestions.
posted by bolognius maximus at 6:49 PM on December 6, 2009

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