COOH synthesis

1. Jan 20, 2005

tipton12

Having trouble with this one; I've tried working backwards from the three carbon carboxylic acid product, but to no avail. Please help!! I can not figure out 'K'.

"A hydrocarbon K adds one equivalent of H2 upon hydrogenation over a Pt catalyst. When K is oxidized vigorously with hot KMnO4, a single three carbon carboxylic acid is obtained. Give the structures of K and the carboxylic acid."

This seems simple but K is giving me a lot of grief.

2. Jan 20, 2005

chem_tr

Well, vigorous reaction with hot permanganate is not still enough for pure hydrocarbons, this is an alkene with single double bond, this is okay. Since decarboxylation won't occur with KMnO4, I think the K hydrocarbon has three carbons. The vinylic hydrocarbon $$H_3C-CH=CH_2$$ may be the structure for K and the corresponding carboxylic acid may be $$HOOC-CH=CH_2$$. I think the carboxylic acid should be like this, since it is principally similar with an aromatic alkane, say, toluene, which can also be oxidized with permanganate to the acid.

I may be wrong, so you will have to finish the remaining work by yourself.

3. Jan 20, 2005

movies

Sounds like a symmetrical alkene to me. Probably 3-hexene.

4. Jan 20, 2005

chem_tr

Hmm, does permanganate cleave double bonds to give carboxylic acid? I couldn't remember this one. However, this is logical. I remember ozonolysis to produce ketones or aldehydes, so this sounds okay to me.

EDIT: I looked up my textbook and saw the example with cyclohexene to give adipic acid with hot permanganate. So your assumption is okay, I think.

Last edited: Jan 20, 2005
5. Jan 20, 2005

tipton12

I'll play around with both ideas and get back to you on my answers. Thank you both for all your help!!!

6. Jan 20, 2005

movies

Yeah, I think KMnO4 first does a dihydroxylation, much like OsO4, and then cleaves the diol, much like NaIO4 does. The resulting aldehydes are then oxidized to the acids.

7. Feb 23, 2005

tipton12

sorry i never got back to writing my answer. I waited for it to be graded.
This is what I did and it was marked correct:

K ____H2/Pt___K ____Oxidized___KMnO4/heat___ 3-hexene___H2/Pt___hexane w/carbocation on the 3carbon_____warm KMnO4/-OH___>> HO-C-CH2-CH3
ll
O

Thanks for your help!

8. Feb 23, 2005

tipton12

i don't know why my answer posted that way, but the =O is supposed to be on the Carbon attached to the -OH.