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Topic: How to add a double bonded oxygen to an alkane?  (Read 9781 times)

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Offline clara226

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How to add a double bonded oxygen to an alkane?
« on: December 04, 2011, 01:13:03 AM »
I was wondering, let's say you had CH3-(CH2)2-CH3, how could you add a double bonded oxygen (like a carbonyl group) to one of the middle carbons?

The only thing I can think of is adding NBS, then doing an E2 using heat and methoxide to get an alkene, then maybe adding MCPBA and hydroxide ion to form an epoxide, then doing an acid-catalyzed opening of the epoxide to get trans OH groups, but that leads me to a related question, which was on one of our previous exams -

if you had two anti OH groups on an alkane, how would you be able to turn that into an alkane with just a carbonyl group on it?

So I guess there's two questions - how, in general, would you add a double bonded oxygen to an alkane, and the question I just asked above.

Thanks so much for reading, and I can't tell you how much I'd appreciate it if someone could answer this for me.

Offline obsidianavenger

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Re: How to add a double bonded oxygen to an alkane?
« Reply #1 on: December 04, 2011, 02:05:49 AM »
i think you're overcomplicating this thing. once you make an alkyl halide, you can just use water and Sn1 to get an alcohol, and then oxidize the alcohol using sodium dichromate in sulfuric acid to get the ketone.

to get a ketone from a diol, i *think* you can simply dehydrate it to form an enol and it will tautomerize to the ketone form because that is more stable. i'm not sure how much control you would have in that situation though... it might be that it would dehydrate twice and form an alkyne instead. but i doubt it!

Offline clara226

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Re: How to add a double bonded oxygen to an alkane?
« Reply #2 on: December 04, 2011, 10:24:01 PM »
^Thank you so much!  The second part made sense to me, but for the first part, the only thing is that we didn't learn about reactions with dichromate yet, so I'm not really sure how else I could go about doing this.  Is there a way I  could do it by adding NBS, then eliminating to form a double bond, hydrating it to create an OH group, then adding NBS again, eliminating to form another double bond, and having it tautomerize?

Or if I was able to get a single bonded oxygen attached to an alkane, would one of the pairs of electrons be able to move so that the O would be double bonded to the alkane?  or would I need a reagent to do that, because I don't think we've learned about that yet.  I did learn about PCC from google, but we're not allowed to use that yet because we haven't studied it.
« Last Edit: December 04, 2011, 10:41:58 PM by clara226 »

Offline UG

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Re: How to add a double bonded oxygen to an alkane?
« Reply #3 on: December 05, 2011, 12:27:12 AM »
Is there a way I  could do it by adding NBS, then eliminating to form a double bond, hydrating it to create an OH group, then adding NBS again, eliminating to form another double bond, and having it tautomerize?
Are you still talking about an alkane or something else?

Offline clara226

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Re: How to add a double bonded oxygen to an alkane?
« Reply #4 on: December 05, 2011, 01:43:37 AM »
Is there a way I  could do it by adding NBS, then eliminating to form a double bond, hydrating it to create an OH group, then adding NBS again, eliminating to form another double bond, and having it tautomerize?
Are you still talking about an alkane or something else?

I'm still talking about an alkane, but turning it into an alkene and then adding an OH group so it's an alkane with an alcohol group.  I hope that makes sense, I'm not the best at explaining things.

Offline UG

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Re: How to add a double bonded oxygen to an alkane?
« Reply #5 on: December 05, 2011, 04:46:52 AM »
Is there a way I  could do it by adding NBS, then eliminating to form a double bond, hydrating it to create an OH group, then adding NBS again, eliminating to form another double bond, and having it tautomerize?
Let me see if I can follow you, so you add NBS to an alkane, some kind of radical substitution reaction occurs and you get a haloalkane? Then you eliminate HBr to get an alkene. Hydrate the alkene to create an alcohol, then add NBS again, I am not sure what this will do  ???

Offline orgopete

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Re: How to add a double bonded oxygen to an alkane?
« Reply #6 on: December 05, 2011, 10:18:07 AM »
^Thank you so much!  The second part made sense to me, but for the first part, the only thing is that we didn't learn about reactions with dichromate yet, so I'm not really sure how else I could go about doing this.  Is there a way I  could do it by adding NBS, then eliminating to form a double bond, hydrating it to create an OH group, then adding NBS again, eliminating to form another double bond, and having it tautomerize?


Or, perhaps you know the route from a triple bond to a ketone. In that case, brominate the alkene, eliminate to give an alkyne. Hydrate with sulfuric acid to give the ketone after tautomerization.
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