Separation of a Basic (3-nitroaniline) and neutral (menthol) compound

[BIG]

Hey guys, new member here, i always have a hard time writing my lab discussion for organic because i dont really understand it that well, and hoping someone can give me a lending hand,

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What happens when NaOH is added to 3-nitroaniline??, i know a yellow color appears, but can someone give me an explanation as to what actually happens and what the color indicates??

Edited January 22, 2010 by BIG
Consecutive posts merged.

[stonedcarli]

actually, mothing happens. NaOH solvates it, thats all.

 

You see, the only thing that could happen is that OH deprotonates the amine which is unlikely because amine is a very weak acid.

Edited January 22, 2010 by stonedcarli

[akcapr]

If it changes color that means a reaction likely occured. With the added EW/staibilizing effect of NO2 group id say it got deprotonated. WIth a pKa of about 2.5, its fairly acidic.

[Horza2002]

If it changes color that means a reaction likely occured. With the added EW/staibilizing effect of NO2 group id say it got deprotonated. WIth a pKa of about 2.5, its fairly acidic.

 

The nitro group is in the wrong place to help stabilise the anion. Its meta to the amine so will only have a tiny stabilisng effect. If it was ortho or para to the amine it MIGHT b able to deprotante the amin but i seriously doubt it. 2,4,6 tri nitro aniline might be ok...

[akcapr]

to me it seems that the meta position is the most stabilizing for the anion. Or at least i think you could be able to protonate, and seperate it that way from the nuetral compound, if thats the goal. Or perhaps its forming some sort of complex

[John Cuthber]

Wiki gives a pKa of 2.47

Since it changes colour there's something going on; deprotonation seems a good bet.

This base is an acid.

[Horza2002]

akcapr, draw curly arrows for the anion and you'll find that meta is the only poistion a nitro group will no stabilise the anion

[akcapr]

well all the positions have the same number of resonance structures the meta position just has the best one. correct me if im wrong

[Horza2002]

Ive drawn out what I mean. It doesn't matter if they have the same number of resonance srcutures, its how stable the anion is what is important. In the case when the nitro is meta, the anion can't be stabilised by the electron withdrawing nitro group. However, when the nitro is ortho or para, it has no problem in being stbaiulised by the nitro group.

 

An anion on oxygen is far more stable than one on carbon (electronegativity). And remember that nitro groups are one the most electron withdrawing you can have.

 

 

[akcapr]

ok gotcha