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Questions and Answers
What is the chemical name for aspirin?
What is the chemical name for aspirin?
What is the molecular formula of aspirin?
What is the molecular formula of aspirin?
In which solvent is aspirin most soluble?
In which solvent is aspirin most soluble?
What happens to aspirin when it comes in contact with moisture?
What happens to aspirin when it comes in contact with moisture?
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Why is the melting point of aspirin not a reliable indicator of its purity?
Why is the melting point of aspirin not a reliable indicator of its purity?
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Which method of synthesizing aspirin is preferred due to the safety and simplicity of the reagents used?
Which method of synthesizing aspirin is preferred due to the safety and simplicity of the reagents used?
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What is the role of pyridine in the second method of aspirin synthesis?
What is the role of pyridine in the second method of aspirin synthesis?
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What does a negative result in the ferric chloride test indicate about aspirin?
What does a negative result in the ferric chloride test indicate about aspirin?
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Compared to acetic anhydride, what is a major disadvantage of using acetyl chloride in the synthesis of aspirin?
Compared to acetic anhydride, what is a major disadvantage of using acetyl chloride in the synthesis of aspirin?
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In which step of the reaction mechanism does the carbonyl oxygen get protonated?
In which step of the reaction mechanism does the carbonyl oxygen get protonated?
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What is the primary reason that acetyl chloride is avoided in aspirin synthesis despite being more reactive?
What is the primary reason that acetyl chloride is avoided in aspirin synthesis despite being more reactive?
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Which compound gives a positive result in the ferric chloride test due to the presence of a phenolic group?
Which compound gives a positive result in the ferric chloride test due to the presence of a phenolic group?
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What is the order of effectiveness for the acetylation agents mentioned in the synthesis of aspirin?
What is the order of effectiveness for the acetylation agents mentioned in the synthesis of aspirin?
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Study Notes
Aspirin Synthesis
- Aspirin is also known as 2-acetyl salicylic acid or 2-acetoxy benzoic acid.
- Its molecular formula is C₉H₈O₄, and its molecular weight is 180.15.
- Aspirin appears as colorless crystals or a white crystalline powder.
- It has a slightly acidic taste and no odor.
- Aspirin is slightly soluble in water (1:300 at 25°C, 1:100 at 37°C). It is more soluble in organic solvents like ether, ethanol, and chloroform.
Stability
- Aspirin (ASA) is stable in dry air when in crystal or powder form.
- In the presence of moisture, it undergoes hydrolysis to form salicylic acid and acetic acid.
- This hydrolysis occurs through base catalysis, where water molecules attack the carboxylate anion.
Mechanism
- The mechanism of aspirin synthesis involves a reaction between salicylic acid and acetic anhydride.
- The reaction is catalyzed by a weak acid (e.g., sulfuric acid). A detailed chemical reaction is shown.
Identification Test
- The presence of a phenolic group in a molecule can be detected using a ferric chloride test.
- During this test, applying ferric chloride, a violet-colored iron complex signifies the presence of a phenolic group.
- Aspirin doesn't have this group; hence it gives a negative result. Conversely, salicylic acid gives a positive test.
Methods of Synthesis
- Method 1: Uses acetic anhydride, which is readily available, easy to handle, and doesn't produce corrosive HCl gas. The process for this method is described in detail.
- Method 2: Uses acetyl chloride. This method is more vigorous, producing corrosive HCl gas, and pyridine is a teratogenic air pollutant, so this method generally is avoided.
Procedure for Method 1
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Steps for producing aspirin using acetic anhydride:
- Place 1 gram of salicylic acid in a dry flask.
- Add 2 ml of acetic acid.
- Carefully add 1-2 drops of concentrated sulfuric acid (H₂SO₄).
- Heat and stir until all the salicylic acid dissolves.
- Allow the mixture to cool to obtain the aspirin crystals.
- Add some water and filter the product.
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Important Notes:
- If aspirin crystals haven't formed, add water to destroy excess acetic anhydride.
- Acetic acid, or excess sulfuric acid, is not added, because those substances lead to hydrolysis of the aspirin.
Calculating Percentage Yield
- The steps to calculate the yield of aspirin are shown
- The theoretical yield is calculated using the mole ratios of the reactants and products.
- The actual yield is the mass of aspirin that was collected in the reaction.
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Description
Explore the synthesis, stability, and identification tests of aspirin in this informative quiz. Learn about its molecular structure, chemical properties, and the mechanism of its formation. Test your knowledge of aspirin's characteristics and its behavior in different conditions.
