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Topic: Convert methyl bromide to 2-methoxypropane  (Read 4783 times)

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Offline neobenzene

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Convert methyl bromide to 2-methoxypropane
« on: October 14, 2012, 10:50:52 PM »

Hi..I got this question on a test yesterday; I got up to a certain point after which I didn't know what to do.

The question : Convert methyl bromide to 2-methoxy propane

I know methyl bromide is CH3Br and 2-methoxy propane is CH3-CH(OCH3)-CH3

This is what I did

1) React CH3Br with CHCNa (Sodium ethynide) to form propyne
2) Hydrogenate propyne with a nickel catalyst (Propyne + 2H2) to form propane (CH3-CH2-CH3)
3) Now I want to add a methoxy group (OCH3) to the carbon #2. How do I do that?

But before that, is this sequence of steps correct?

Offline discodermolide

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #1 on: October 14, 2012, 10:55:45 PM »
You should not have hydrogenated it all the way to an alkane. There are plenty of methods that will stop it at the alkene level.
So find such a method and see where you can go from there.
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Offline neobenzene

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #2 on: October 14, 2012, 10:57:49 PM »
Ok..so instead of adding 2H2, I'll add H2 in the presence of nickel to give me propene.

Offline discodermolide

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #3 on: October 14, 2012, 11:00:52 PM »
No that will do a complete hydrogenation. Try a Lindlar catalyst.
When you get to propene what's next?
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Offline neobenzene

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #4 on: October 14, 2012, 11:03:32 PM »
I'm not sure

Offline discodermolide

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #5 on: October 14, 2012, 11:06:36 PM »
Try consulting a textbook or google it!
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Offline neobenzene

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #6 on: October 14, 2012, 11:09:55 PM »
Can you give me a hint, if that's possible?


Offline neobenzene

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #8 on: October 14, 2012, 11:18:13 PM »
So, if I add H2SO4 to propene, I will get (CH3)2-CH-O-SO3H. If I hydrolyse that, I will get CH3-CHOH-CH3

So all I need to do is to replace the "H" in the "OH" by a "CH3" group. Do I do Friedel Craft's alkylation?

Offline discodermolide

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #9 on: October 14, 2012, 11:22:35 PM »
No you do a Williamson's ether synthesis.
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Offline neobenzene

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Re: Convert methyl bromide to 2-methoxypropane
« Reply #10 on: October 14, 2012, 11:27:25 PM »
Thank you!

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