[newkiddonblock]

 

Would using Br and H₂O work for the first one?

[Schrödinger]

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?

[newkiddonblock]

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:

[newkiddonblock]

What about the second reaction though?
I don't get it

[discodermolide]

You have "epoxidised" the double bond. But in your subsequent products it is still there. Remove it and see how you get on.

[newkiddonblock]

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??

[newkiddonblock]

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^-?

[discodermolide]

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?

[newkiddonblock]

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?

[newkiddonblock]

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?

[discodermolide]

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.

[discodermolide]

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!!

[newkiddonblock]

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?

[newkiddonblock]

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)  methanol (CH₃OH) must be present

Is it the same as...

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

[discodermolide]

What would methanolic HBr solution give you?