Practical Review Lab 4: Preparation of p-Nitroaniline

What were the three steps used to synthesize p-nitroaniline from aniline?

(1) Acetylation of aniline (2) Nitration of acetanilide (3) Deacylation of nitro acetanilide

What are the two reasons that this synthesis could not have occurred in one step?

(1) The NH2 on the aniline would have oxidized (2) Only the para product was desired so a sterically hindered base had to be added to prevent addition of NO2 in ortho spot

How did the nitration of acetanilide occur?

-Acetanilide, acetanilide and acetic acid reacted at room temperature -Ice and sulfuric acid where then added -Sulfuric and nitric acid then added in 1:1 ratio

What happened during the acetylation of aniline? Why was this done?

-An acetyl protecting group was added to nitrogen on the aniline. -Done to prevent it from oxidizing and the protecting group is sterically hindered and directed to para position.

How did the deacylation of nitroacetanilide occur?

-Hotplate heated p-nitroacetanilide, water, and HCl -NH3 was added when solution was in crushed ice to remove H

What ratio was the sulfuric acid and nitric acid added?

1:1

How did the acetylation of aniline occur?

A hotplate was used to heat aniline, acetic acid, and acetic anhydride. Water condenser was used to prevent evaporation.

How were all three steps crystallized? Why?

By placing the chemicals into small beakers of ice. Because these are acids and you ALWAYS ADD ACID.

What is the recrystallization technique based on?

Concentration and solubility

What method is used to remove a solvent from a product dissolved in solution? (Hint: Only needed if you didn't produce enough product for vacuum filtration)

Evaporator

What was the purpose of the acetic acid in the acetylation of aniline?

It was both the solvent and the catalyst.

What method is used to precipitate and purify a chemical out of a solution?

Recrystallization

What was the purpose of the sulfuric acid in the nitration of acetanilide ?

Served as a dehydrating agent

What was the purpose of the experiment?

Synthesize p-nitroaniline from aniline in three steps

Why was reflux present?

The boiling point of the solvent was the same temperature as the reaction

In the deacylation of nitroacetanilide, why was NH3 added to the crushed ice?

To remove the hydrogen from the NH3

How were the crystals removed from the unwanted solution in each step?

Vacuum filtration

What was the function of the water and HCl in the deacylation of nitroacetanilide?

Water was the solvent and HCl was the reactant

How did we know that the solution was basic enough (that enough NH3 had been added)?

We used pH paper and waited for it to turn blue.