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.
Introduction to Preparation of p-Nitroacetanilide
Nitration is an important reaction that is used within the training of nitro compounds. Nitro compounds are used as beginning substances for lots of commercially beneficial materials consisting of dyes, pills, explosives, and so forth. In this experiment, you'll put together p-nitroacetanilide through the nitration of acetanilide.
Main Objective of p-Nitroacetanilide
After conducting this experiment, you should be capable of:
Putting together p-nitroacetanilide,
Recrystallise the p-nitroacetanilide.
Principle of p-Nitroacetanilide
The p-Nitroacetanilide is prepared via nitration of acetanilide. The acetamido institution (-NHCOCH3) in acetanilide is ortho and para directing. therefore, on nitration a aggregate of o- and p-nitroacetanilide is shaped:
The acetamido organization being a bulky group causes steric challenge at the ortho function. Therefore, p-nitroacetanilide is fashioned as the primary product. . On crystallization from ethyl alcohol, p-nitroacetanilide crystallizes out as nearly colorless crystals even as the ortho isomer stays in solution.
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.
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:
Results and Discussion
The p-Nitroacetanilide yield is _____ grams.
Precautions:
Temperature has to not exceed extra than 20 degree C.
beneficial to feature nitric acid into the reaction aggregate even as it is immersed in ice-bath
upload fuming nitric acid drop through drop cautiously and do not inhale the fumes of nitric acid.
make sure you have been nicely educated within the threat communique general.
identify the chemical substances you're using.
hold a stock of all chemicals being stored at your place of work. make certain to list the quantities, garage location and storage technique.
Ask your chemical supplier for protection information Sheets and preserve them on hand for reference.
Label all boxes with the name, awareness, manufacturing date and statistics on the hazards associated with the chemical being saved.
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 on Preparation of p-Nitroacetanilide
1. What is p-nitroacetanilide and how is it prepared in a laboratory setting?
p-Nitroacetanilide, or N-(4-nitrophenyl)acetamide, is an organic chemical compound. It is prepared in the lab through the electrophilic nitration of acetanilide. This process involves treating acetanilide with a nitrating mixture, which is a combination of concentrated nitric acid and concentrated sulphuric acid, while carefully controlling the temperature.
2. What is the specific role of the 'nitrating mixture' in this reaction?
The nitrating mixture is essential for generating the electrophile required for the reaction. Concentrated sulphuric acid acts as a catalyst; it protonates the nitric acid, which then loses a water molecule to form the highly reactive nitronium ion (NO₂⁺). This nitronium ion is the electrophile that attacks the benzene ring of acetanilide to form p-nitroacetanilide.
3. In the nitration of acetanilide, why is the para-product formed as the major product, while the ortho-product is minor?
The acetamido group (-NHCOCH₃) on the acetanilide ring is an ortho-para directing group. However, this group is quite bulky. Due to steric hindrance, the large nitronium ion (NO₂⁺) finds it physically difficult to attack the ortho positions, which are adjacent to the bulky acetamido group. The para position is less crowded, making it the preferred site for electrophilic attack, thus resulting in p-nitroacetanilide as the major product.
4. Why must the reaction temperature be kept low (below 20°C) during the addition of the nitrating mixture?
Maintaining a low temperature is crucial for two main reasons. Firstly, the nitration reaction is highly exothermic (releases heat), and keeping it cool prevents the reaction rate from becoming uncontrollably fast. Secondly, higher temperatures can lead to unwanted side reactions, such as dinitration (the addition of a second nitro group) or the oxidation of the benzene ring, which would decrease the yield of the desired p-nitroacetanilide product.
5. What is the importance of converting aniline to acetanilide before carrying out nitration?
This is a critical step involving the concept of a protecting group. The amino group (-NH₂) in aniline is highly activating and gets readily oxidised by strong acids like nitric acid, leading to tarry, undesirable products. By converting aniline to acetanilide, the amino group is protected. The acetamido group (-NHCOCH₃) is only moderately activating and is not susceptible to oxidation, allowing the nitration to proceed smoothly and yield the desired nitro-product.
6. How is the crude p-nitroacetanilide purified from the reaction mixture?
The crude p-nitroacetanilide is purified using the technique of crystallisation. Because the ortho-isomer is more soluble in ethanol than the para-isomer, the mixture can be dissolved in a minimum amount of hot ethanol. Upon cooling, the less soluble p-nitroacetanilide crystallises out as pure, pale yellow crystals, while the more soluble ortho-isomer and other impurities remain dissolved in the solvent. The pure crystals can then be separated by filtration.
7. What are the main uses or applications of p-nitroacetanilide?
p-Nitroacetanilide serves as an important intermediate in the synthesis of various other compounds. Its primary uses include:
- The preparation of p-nitroaniline, which is a key component in creating azo dyes.
- The synthesis of pharmaceutical drugs like paracetamol and phenacetin.
- Its use in the manufacturing of certain pesticides and rubber chemicals.
