Preparation of p-Nitroacetanilide

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What is p-Nitroacetanilide?

Para nitro acetanilide is also referred to as 4-Nitroacetanilide. Para nitro acetanilide is defined as a chemical compound that is a derivative of nitro acetanilide prepared from the mixture of nitrating and acetanilide. Along with the para product, a trace of ortho product is also formed.

Other names of p-Nitroacetanilide can be given as p-Acetamido Nitrobenzene, N-(4-nitrophenyl) acetamide, N-Acetyl-4-nitroaniline, and p-Nitroacetanilide.


Introduction

Nitration is described as an important reaction that is used in the nitro compound preparation. These nitro compounds can be used as starting materials for several essential commercially useful materials like drugs, dyes, explosives, and more. In this experiment, we will prepare the p-nitro acetanilide by the acetanilide nitration.


Objectives

After performing this experiment, we should be able to:

  • recrystallize the p-nitro acetanilide,

  • prepare p-nitro acetanilide,

  • determine the melting point of prepared p-nitro acetanilide, and

  • perform the other compounds nitration


Preparation of para nitro acetanilide from acetanilide

Let us know about the preparation of para nitro acetanilide below:

Aim

To prepare the p-Nitroacetanilide from acetic acid and acetanilide in the presence of nitrating mixture.


Theory

The organic compound p-nitro acetanilide can be prepared from the acetanilide through nitration. When acetanilide is treated with the nitrating mixture, that is, a mixture of sulphuric acid and nitric acid, it forms p-nitro acetanilide. Also, along with p-nitro acetanilide, as a minor product, o-nitro acetanilide is also formed. Since o-nitro acetanilide is much soluble in alcohol, it is so easy to isolate p-nitro acetanilide through crystallization.

The chemical reactions involved in this process can be given as follows:

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It is a type of electrophilic substitution reaction. Here, the electrophile -NO2 will attach the para position because the -NHCOCH3 is considered as an electron releasing group. And nitro anilines will be prepared by this form of reaction, since if it is not possible to nitrate aniline, the amino group would be oxidised with a nitrate mixture. Also, in order to protect the amino group from oxidation, first, acetanilide is nitrated to produce p-nitro acetanilide and then on hydrolysis to produce p-nitroaniline, which is difficult to obtain by direct nitration.


Materials Required

The essential materials that are required for the preparation of p-Nitroacetanilide can be listed as follows:

  • Acetic acid

  • Acetanilide

  • Fuming Nitric acid

  • Concentrated Sulphuric acid

  • Ethyl alcohol

  • Beaker

  • Conical flask

  • Filter paper

  • Dropping funnel

  • Buchner funnel

  • Glass rod

  • Pipette


Apparatus Setup

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Procedure

  • Take 3 grams of finely powdered acetanilide in a clean beaker and then dissolve it by adding glacial acetic acid by carefully stirring the content at room temperature.

  • Now, warm the mixture gently to dissolve acetanilide completely.

  • Then, cool the solution and slowly add the concentrated sulphuric acid with constant stirring. By doing so, the solution becomes warm. Then, keep the mixture in an ice-bath, and a clear solution is obtained.

  • Now, add fuming nitric acid dropwise through a dropping funnel with constant stirring to the cool solution.

  • During this whole process, always maintain the temperature below 20℃.

  • Once the addition of nitric acid is over, the beaker can be removed from the freezing mixture bath and allowed to stand at room temperature for half an hour.

  • In a beaker, pour the mixture into 100 grams of crushed ice and stir well.

  • By doing so, large crystals of p-nitro acetanilide are obtained and then filter those crystals via filter paper.

  • The separated p-nitro acetanilide is washed with cold water to remove excess acid.

  • It is then crystallized from ethyl alcohol. Now, dry the crystals in filter paper folds and weigh them to know the yield.


Observations

Let us look at the sample observations, which are tabulated below:

Color of the Crystals

Colorless

Expected Yield

4 Grams

Melting Point

214℃


Results and Discussion

The p-Nitroacetanilide yield is _____ grams.


Precautions

  • The temperature should not exceed greater than 20℃.

  • It is also advisable to add nitric acid into the mixture of reaction while it is immersed in an ice-bath

  • Also, add fuming nitric acid carefully in a drop by drop method and do not inhale the nitric acid fumes.


Principle

p-Nitroacetanilide can be prepared by acetanilide nitration. The acetamido group (which is -NHCOCH3) in acetanilide is para and directing. Thus, on nitration, an o- and p-nitro acetanilide mixture is formed:

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Acetamido group, being a bulky group, will cause the steric hindrance at the position of ortho. Thus, the p-nitro acetanilide can be formed as a major product. Also, when crystallised from ethyl alcohol, the p-nitro acetanilide crystallises mostly as colourless crystals, whereas, the ortho isomer remains in the same solution.


Safety

Let us look at the safety points of p-Nitroaniline.

Ethanol is flammable, so it is advised to handle with care. Sodium acetate trihydrate (which is CH3COONa.3H2O), acetophenone oxime, and the acetophenone irritates the human eyes, ears, and respiratory system, if came into contact. It is advised to avoid direct or indirect contact and does not inhale or ingest. Hydroxylamine hydrochloride (NH2OH.HCl) is defined as corrosive; hence, avoid all contact and handle this compound with caution. Deuterochloroform (CDCl3) is defined as toxic, so it also should be handled with care.


FAQs (Frequently Asked Questions)

1. What is a nitrating mixture called?

The concentrated fuming nitric acid and the sulphuric acid combination is referred to as nitrating mixture.

2. How does the p-nitro acetanilide get separated from o-nitro acetanilide in the sample of crude?

o-nitro acetanilide is given as more soluble in ethanol. So, it remains in the mother liquor, and also, during crystallization, only p-nitro acetanilide gets separated.

3. Why is the para product major and ortho derivative minor? State with a reason.

Here, the reaction is described as an electrophilic substitution reaction, and the nitronium ion that is formed is directed towards para and ortho positions. Because of the steric hindrance in the ortho position, the nitronium electrophile can be directed more towards the para position. Thus, the para product is given as major.

4. Give the formula for p-nitro acetanilide, including its IUPAC name.

The formula for the p-nitro acetanilide is given as C8H8N2O3, and the IUPAC name for the same is N-(4-nitrophenyl) acetamide.

5. List the uses of p-nitroacetanilide.

Some of the uses of p-nitroacetanilide can be listed as follows:

  • It can be used in pharmaceuticals in the preparation of phenacetin and paracetamol.

  • It is also used in pesticides, and in addition, rubber chemicals are also used as an intermediate for dyes.