Base Extraction- help!

[meant2be10]

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If you have aniline, p-nitro aniline, and CH3NO2 in a chloroform soln, how do you extract each of the compounds??

The answer (this is from Kaplan, OChem test 3, problem 12) says to
1)use a weak acid to extract the strongest base (aniline), then
2) use a stronger acid to extract the p-nitro aniline from the CH3NO2
3)use distillation

Wouldn't a weak acid in the first step separate out the weakest base? Why would it is separate out the strongest base?? Please help!

 

[RCT PC CRN]

Weak acid react with Strong base. It won't react with weak base. Once you have extracted Strong base (Aniline here) you can use Strong acid to extract weak base (p-nitroaniline) from neutral compound (CH3NO2).

Just a thought, 2 weak don't go together.😉

This is a basic theme for extraction. It goes same for any mixture of Strong, weak and neutral compound.

Step 1. Treat the mixture with Weak so the strong will react and you can extract the product.

Step 2. Treat the remaining mixture with strong so the weak will be out and you will be left with neutral compound.

Hope this helps.

If you have aniline, p-nitro aniline, and CH3NO2 in a chloroform soln, how do you extract each of the compounds??

The answer (this is from Kaplan, OChem test 3, problem 12) says to
1)use a weak acid to extract the strongest base (aniline), then
2) use a stronger acid to extract the p-nitro aniline from the CH3NO2
3)use distillation

Wouldn't a weak acid in the first step separate out the weakest base? Why would it is separate out the strongest base?? Please help!

 

[meant2be10]

Ah, ok, that makes sense! Thank you!

 

[nainaaz]

If you have aniline, p-nitro aniline, and CH3NO2 in a chloroform soln, how do you extract each of the compounds??

The answer (this is from Kaplan, OChem test 3, problem 12) says to
1)use a weak acid to extract the strongest base (aniline), then
2) use a stronger acid to extract the p-nitro aniline from the CH3NO2
3)use distillation

Wouldn't a weak acid in the first step separate out the weakest base? Why would it is separate out the strongest base?? Please help!

A strong base (here aniline) easily accepts protons and can readily get protonated either in presence of weak or strong acid. whereas weak bases (p-nitro aniline) only gets protonated in presence of strong acid.

Understanding this concept, if we first do the extraction with weak acid, strong base (aniline) will easily gets protonated and hence easily separated. On the other hand if we would have used strong acid both aniline and P-nitro anilne would have been protonated...therefore hard to seperate.

hope it helps

 

[RCT PC CRN]

Ah, ok, that makes sense! Thank you!

You are very welcome.