tbr ochem

[echoyjeff222]

@justadream

you asked this question ...

TBR page 206 #10

“To separate an amine from an amide, it would be best to use which of the following for extraction:”

1. Ether and water at pH = 3
2. Ether and water at pH = 7
3. Ether and water at pH = 11
4. Amides cannot be separated from amines

However, I thought it was D. if you use aqueous solution with amides, won't they just get destroyed (hydrolyzed)?

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[texan2414]

@justadream

you asked this question ...

TBR page 206 #10

“To separate an amine from an amide, it would be best to use which of the following for extraction:”

1. Ether and water at pH = 3
2. Ether and water at pH = 7
3. Ether and water at pH = 11
4. Amides cannot be separated from amines

However, I thought it was D. if you use aqueous solution with amides, won't they just get destroyed (hydrolyzed)?

Amides are relatively low on the reactivity scale so its hard to force hydrolysis of them.
Btw, is the answer C (choice 3)? At pH 11, amine would be deprotonated thus becomes easier to extract it in the aqueous layer whereas the amide would probably be unreacted and be present in the organic layer.

 

[echoyjeff222]

Amides are relatively low on the reactivity scale so its hard to force hydrolysis of them.
Btw, is the answer C (choice 3)? At pH 11, amine would be deprotonated thus becomes easier to extract it in the aqueous layer whereas the amide would probably be unreacted and be present in the organic layer.

Hydrolysis, especially in acidic conditions, should be fairly common ...

Amines need to be protonated to come out of solution (NH3+), thus we need an acidic solution. pH = 3 would be best.

 

[justadream]

@justadream

you asked this question ...

TBR page 206 #10

“To separate an amine from an amide, it would be best to use which of the following for extraction:”

1. Ether and water at pH = 3
2. Ether and water at pH = 7
3. Ether and water at pH = 11
4. Amides cannot be separated from amines

However, I thought it was D. if you use aqueous solution with amides, won't they just get destroyed (hydrolyzed)?

Lol I did? I don't remember.

The answer is A because you want one of the species to be much more soluble in one layer than the other.
Since amine is a base, if you add acid, you will make NH3+ which is very soluble in the water layer. The amide will be mostly unaffected by the acid so it will just go to the ether layer.

You are right that amides can by hydrolyzed by acid. I think you need HEAT to make it happen, however.

 

[echoyjeff222]

I'm just going to say this is a bad question because you're going to destroy at least some of the amide ... >.>

 

[texan2414]

Oh woops yeah - mixed carboxylate with amide.

Thanks,