[silverre]

Hi all
I have some questions for my chemistry lab.
First, it is the nitration of acetanilide by adding NO2 to the para position of acetanilide.
Acetanilide is dissolved in glacial acetic acid by warming on a water bath.
Why is acetic acid chosen as the solvent here?

Next the solution is cooled and 5ml of concentrated sulfuric acid is added dropwise. What is the function of sulfuric acid in the acetanilide/acetic acid solution? Is it to increase the melting point of the mixture or to make the mixture more acidic so that adding the nitrating mixture later results in a faster reaction?

Finally the nitrating mixture is added in an ice bath. After leaving to stand for about 10 minutes, the mixture is added to ice water. As the mixture was added to ice water, i noticed that the mixture started to precipitate into a yellowish solid which was para-nitroacetanilide.
What is the function of the ice water here??

in order to get para-nitroaniline, para-nitroacetanilide was hydrolysed in hydrochloric acid. What is the function of hydrochloric acid? does it act as a catalyst to cleave the amide bonds? Is it possible to hydrolyse under basic conditions as well??

Thanks for reading!!

[zsinger]

Forum Rules, You must provide us with your answers as you think they might be .  We are happy to assist after that.
          -Zack

[AlphaScent]

What is the nitrating mixture??

You are missing a step where you add any reagent with a nitro group in it at all.

What is the standard way of nitrating a aromatic compound? (i.e. list of reagents for this reaction?)

[silverre]

What is the nitrating mixture??

You are missing a step where you add any reagent with a nitro group in it at all.

What is the standard way of nitrating a aromatic compound? (i.e. list of reagents for this reaction?)

oh sorry. the nitrating mixture was forming a No2+ by adding HNO3 to H2SO4.
acetic acid added to acetanilide (acetanilide used as the CH3C=O group protects the amine group when adding nitrating mixture)
then add conc H2SO4
Then the nitrating mixture is added.
Then the whole mixture is added to ice water, p-nitroacetanilide precipitates?
Filter and dissolve p-nitroacetanilide in water
Add Conc HCL
Reflux in condenser till a orange solution
Add Base (conc NH3) to precipitate p-nitroaniline
filter and Recrystallize to get pure p-nitroaniline (and a by product of ortho-nitroaniline?) 

Forum Rules, You must provide us with your answers as you think they might be .  We are happy to assist after that.
          -Zack

I thought I gave my ideas after every question?
First the question was the function of acetic acid. I only know it as a solvent. Are there any special features of acetic acid for it to be chosen as a solvent?

Next they asked what is the function of Adding sulphuric acid to the acetanilide/acetic acid solution(note I havnt added the nitrating mixture yet. The nitrating mixture was prepared by adding HNO3 to H2SO4.) I can only think of it as to increase the melting point of the mixture? as glacial acetic acid has very low melting point at 16 degree Celsius.

After adding nitrating mixture and left for the reaction to finish, ice water is added. And they asked for the purpose of ice water. Really stuck here. Don't really know why the product precipitates upon adding ice water. I am guessing something to do with the NO2- functional group?

Finally, the HCL that is added during hydrolysis of the amide functional group. I know it is to cleave off the amide bonds but I don't get how.

Thanks for reading

[kriggy]

I think the aceit acid is chosen as a solvent because the sulfuric acid might deprotect the amide protecting group. By using acetic acid as a solvent you move the equilibrium to the protected aniline.
Just a guess..

[zsinger]

Funny, none of those explanations are in your initial post .