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Topic: How do I solve for these Alkene and Epoxide Chemistry problems? :(  (Read 11903 times)

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Offline newkiddonblock

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 :'(

Would using Br and H2O work for the first one?

Offline Schrödinger

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #1 on: December 08, 2012, 10:57:50 AM »
Please post your attempts in order to receive any help. Forum rules.

And what do you mean Br and H2O? what brominating agent are you using here?
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Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #2 on: December 08, 2012, 11:12:10 AM »
Please post your attempts in order to receive any help. Forum rules.

And what do you mean Br and H2O? what brominating agent are you using here?

Sorry about that...

This is what I did for the first reaction:

« Last Edit: December 08, 2012, 11:23:42 AM by newkiddonblock »

Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #3 on: December 08, 2012, 11:15:10 AM »
What about the second reaction though?
I don't get it

Offline discodermolide

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #4 on: December 08, 2012, 11:53:56 AM »
You have "epoxidised" the double bond. But in your subsequent products it is still there. Remove it and see how you get on.
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Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #5 on: December 08, 2012, 12:10:14 PM »
You have "epoxidised" the double bond. But in your subsequent products it is still there. Remove it and see how you get on.

Oh oops...ok I removed it...

Wait but for the second one.

I know it's an epoxide ring opening with a base. But how do I determine the missing components of that reaction??

Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #6 on: December 08, 2012, 12:23:05 PM »
This is what i did...

How did they get the CH3O on the top of the product though??




Oxygen has to be protonated from H+(compound-)

The other missing component (after Br2) would have to be H+CH3-?
« Last Edit: December 08, 2012, 12:33:09 PM by newkiddonblock »

Offline discodermolide

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #7 on: December 08, 2012, 12:34:20 PM »
Two things, watch your stereochemistry, and if you have a methyl ether formed then there must be methanol present.
Why are you using Br2? Do you have to? Can you use HBr?
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Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #8 on: December 08, 2012, 12:44:00 PM »
Two things, watch your stereochemistry, and if you have a methyl ether formed then there must be methanol present.
Why are you using Br2? Do you have to? Can you use HBr?

Well I just wouldn't be using H-Br because the oxygen won't get protonated right away... Also, this isn't an acid epoxide reaction...
The nucleophile from Br-Br will readily attack the less sterically hindered carbon.

And about the whole methyl ether produced from methanol thing...
So, whenever I have a problem like this, where I have something at the top right beside oxygen (O), do I always ask myself what compound that can be derived from?

Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #9 on: December 08, 2012, 12:47:26 PM »
Two things, watch your stereochemistry, and if you have a methyl ether formed then there must be methanol present.
Why are you using Br2? Do you have to? Can you use HBr?

Also, why would the answer be CH3OH instead of CH3-H??
I don't get it.
Because if the Oxygen in the diagram I drew wants to be protonated, then you'd just need CH3 (the molecule in the product) attached to H+, no?

Offline discodermolide

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #10 on: December 08, 2012, 12:49:05 PM »
Why should bromine attack an epoxide? To get ring opening you will have to protonate the epoxide oxygen atom.
And again if you form a methyl ether methanol must be present.
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Offline discodermolide

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #11 on: December 08, 2012, 12:50:15 PM »
Two things, watch your stereochemistry, and if you have a methyl ether formed then there must be methanol present.
Why are you using Br2? Do you have to? Can you use HBr?

Also, why would the answer be CH3OH instead of CH3-H??
I don't get it.
Because if the Oxygen in the diagram I drew wants to be protonated, then you'd just need CH3 (the molecule in the product) attached to H+, no?

CH3 attached to H is methane!!
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Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #12 on: December 08, 2012, 12:52:47 PM »
Why should bromine attack an epoxide? To get ring opening you will have to protonate the epoxide oxygen atom.
And again if you form a methyl ether methanol must be present.

Idk :(
That's what my teacher said in his solution key: the answer on top of the arrow says
Br2/CH3OH


So that's what I assumed...
Is that assumption wrong?

Offline newkiddonblock

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #13 on: December 08, 2012, 12:58:00 PM »
Why should bromine attack an epoxide? To get ring opening you will have to protonate the epoxide oxygen atom.
And again if you form a methyl ether methanol must be present.

Ok so that's like a general rule...

If you form methyl ether (CH3O)  :rarrow: methanol (CH3OH) must be present

Is it the same as...

If you form OH  :rarrow: an acid (H-Nucleophile) must be present

Offline discodermolide

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Re: How do I solve for these Alkene and Epoxide Chemistry problems? :(
« Reply #14 on: December 08, 2012, 01:00:10 PM »
What would methanolic HBr solution give you?
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