Laboratory Synthesis of Aspirin

Professor Dave Explains
12 Apr 202307:54
EducationalLearning
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TLDRIn this educational video, viewers learn to synthesize aspirin (acetylsalicylic acid) from salicylic acid using acetic anhydride and sulfuric acid as a catalyst. The process includes heating, crystallization, and purification steps, ultimately confirmed by a qualitative test with iron(III) chloride.

Takeaways
  • 🧪 The video covers an organic synthesis experiment where aspirin is synthesized from salicylic acid.
  • 🔬 Aspirin, known chemically as acetylsalicylic acid, is made by reacting salicylic acid with acetic anhydride in the presence of a strong acid catalyst.
  • 🔥 The reaction mixture is heated using a hot water bath to facilitate the synthesis process.
  • 💊 The synthesis involves the introduction of an acetyl group to salicylic acid, converting it into aspirin.
  • 👨‍🔬 Safety precautions are emphasized, including the use of appropriate safety gear due to the presence of irritants and strong acids.
  • 📝 Accurate recording of the mass of reagents and the reaction conditions is important for the experiment.
  • 🧊 Post-reaction, the mixture is cooled to room temperature to initiate the formation of aspirin crystals.
  • 🌡️ An ice water bath is used to ensure complete crystallization of the product.
  • 🕊️ Aspirin crystals are collected through vacuum filtration, and the process is repeated with rinsing to ensure purity.
  • 🔬 Recrystallization is performed to further purify the aspirin, dissolving the crude product in ethanol and hot water, then allowing it to recrystallize.
  • 📊 The purity of the synthesized aspirin is confirmed through a qualitative test using iron(III) chloride, which reacts with phenol rings to indicate the presence of impurities.
  • 📈 The final product's mass is determined by weighing after drying, and the purity is confirmed by its lack of color change with iron(III) chloride.
Q & A

  • What is the main objective of the laboratory session described in the script?

    -The main objective of the laboratory session is to synthesize aspirin, a drug used to reduce pain and inflammation.

  • What is the chemical name of aspirin?

    -The chemical name of aspirin is acetylsalicylic acid.

  • How is aspirin synthesized from salicylic acid?

    -Aspirin is synthesized from salicylic acid by reacting it with acetic anhydride to introduce the acetyl group.

  • What role does the hydroxyl group on salicylic acid play in the synthesis of aspirin?

    -The hydroxyl group on salicylic acid attacks protonated acetic anhydride to pick up the acetyl group, forming acetylsalicylic acid (aspirin).

  • What is the purpose of using a strong acid as a catalyst in the synthesis of aspirin?

    -A strong acid is used as a catalyst to facilitate the reaction between salicylic acid and acetic anhydride, promoting the formation of aspirin.

  • Why is heating the reaction mixture necessary in the synthesis of aspirin?

    -Heating the reaction mixture helps to drive the reaction to completion, ensuring that the aspirin is formed efficiently.

  • What is the purpose of performing crystallization steps in the synthesis of aspirin?

    -Crystallization steps are performed to isolate and purify the aspirin from the reaction mixture.

  • What safety precautions should be taken when handling reagents like ethyl acetate and sulfuric acid?

    -Appropriate safety gear and precautions should be used when handling ethyl acetate, an irritant, and sulfuric acid, an extremely strong acid.

  • How is the reaction mixture heated in the synthesis process?

    -The reaction mixture is heated by placing the flask in a hot water bath, rather than directly on a hot plate, to ensure even heating.

  • What is the purpose of using a glass rod to scratch the sides of the beaker during the crystallization process?

    -Scratching the sides of the beaker with a glass rod provides a surface for crystals to start forming, initiating crystallization.

  • How is the purity of the synthesized aspirin confirmed?

    -The purity of the synthesized aspirin is confirmed using a simple qualitative test with iron(III) chloride, which changes color in the presence of a phenol ring.

Outlines
00:00
🧪 Aspirin Synthesis in the Lab

This paragraph introduces the process of synthesizing aspirin, a common drug used for pain relief and inflammation. The chemical name of aspirin is acetylsalicylic acid, and it can be synthesized from salicylic acid and acetic anhydride in a single step. The method involves adding acetic anhydride to salicylic acid, using a strong acid like sulfuric acid as a catalyst, and heating the mixture. The reaction is carried out in a water bath to ensure even heating. After cooling, aspirin crystals form, which are then isolated and purified through crystallization steps. The process emphasizes the importance of safety gear due to the use of potentially harmful reagents like ethyl acetate and sulfuric acid.

05:03
🔍 Confirming Aspirin Synthesis with Iron(III) Chloride Test

The second paragraph focuses on the verification of the synthesized aspirin's purity and identity. After the synthesis, the product is tested using iron(III) chloride, which changes color in the presence of a phenol ring. Salicylic acid, which contains a phenol ring, turns purple upon the addition of iron(III) chloride, while aspirin, which lacks this ring, remains brown. The experiment involves adding the test reagent to samples of the starting material, crude product, and final product. The results confirm the successful synthesis and purification of aspirin when the final product remains brown, indicating the absence of the phenol ring. This qualitative test serves as a simple yet effective method to validate the synthesis process.

Mindmap
Keywords
💡Organic synthesis
Organic synthesis refers to the process of chemically combining a few simpler compounds to form a more complex molecule. In the context of the video, organic synthesis is the central theme, as the experiment demonstrates the synthesis of aspirin, an organic molecule, from simpler starting materials. This process is crucial in the production of drugs, biomolecules, and industrial materials.
💡Aspirin
Aspirin, also known as acetylsalicylic acid, is a common analgesic and anti-inflammatory drug. It is highlighted in the video as the target molecule for the synthesis process. Aspirin's synthesis is used as an example to teach the basic principles of organic chemistry and laboratory techniques.
💡Salicylic acid
Salicylic acid is a starting material in the synthesis of aspirin. It is an organic compound that contains a phenol ring, which is essential for the formation of aspirin. In the script, salicylic acid is reacted with acetic anhydride to produce acetylsalicylic acid, the final product.
💡Acetic anhydride
Acetic anhydride is the reagent used to acetylate salicylic acid, leading to the formation of aspirin. It is an anhydride with two acetyl groups that can be transferred to other molecules. In the video, it is mixed with salicylic acid to introduce the acetyl group, a key step in aspirin synthesis.
💡Acetyl group
The acetyl group is a functional group with the formula CH3CO-. It is transferred from acetic anhydride to salicylic acid during the synthesis of aspirin, forming the acetylsalicylic acid molecule. The introduction of the acetyl group is a critical reaction in the script, as it changes the properties of salicylic acid to create aspirin.
💡Recrystallization
Recrystallization is a purification technique used to separate and purify a compound from impurities. In the video, after the initial reaction, the aspirin is recrystallized from ethanol and water to remove any remaining starting materials or by-products, ensuring a pure product.
💡Concentrated sulfuric acid
Concentrated sulfuric acid is used as a catalyst in the synthesis of aspirin. It is a strong acid that helps to protonate the acetic anhydride, facilitating the reaction with salicylic acid. The script mentions adding a few drops of this strong acid to the reaction mixture to speed up the synthesis process.
💡Hot water bath
A hot water bath is a technique used to gently heat a reaction mixture. In the script, a hot water bath is set up to heat the reaction containing salicylic acid and acetic anhydride, providing a controlled heating environment to promote the reaction without direct exposure to a heat source.
💡Vacuum filtration
Vacuum filtration is a method used to separate solids from liquids under reduced pressure. In the video, vacuum filtration is used to collect the aspirin crystals after the recrystallization process, ensuring that the crystals are separated from the mother liquor and dried efficiently.
💡Iron(III) chloride test
Iron(III) chloride, or FeCl3, is used in a qualitative test to detect the presence of phenol rings. In the script, this test is applied to confirm the synthesis and purity of aspirin. The color change from brownish-red to purple indicates the presence of a phenol ring, which is not present in aspirin, thus a successful synthesis should show no color change.
💡Pharmacology
Pharmacology is the study of drugs and their effects on the body. The script mentions that aspirin's use as a pain reliever and anti-inflammatory agent was covered in a pharmacology series. This highlights the interdisciplinary nature of chemistry, where synthesized compounds have direct applications in medicine.
Highlights

Introduction to organic synthesis in the lecture series.

Synthesis of aspirin, a drug used for pain and inflammation.

Aspirin's chemical name is acetylsalicylic acid.

Synthesis of aspirin from salicylic acid in one step.

Use of acetic anhydride to introduce the acetyl group.

Role of a strong acid as a catalyst in the reaction.

Heating the reaction to completion.

Crystallization steps to isolate and purify aspirin.

Use of ethyl acetate and sulfuric acid as reagents.

Safety precautions with irritants and strong acids.

Setting up a hot water bath for even heating.

Precise mass recording of salicylic acid.

Mixing of salicylic acid, acetic anhydride, and sulfuric acid.

Use of a ring stand and clamp for flask stability.

Heating the water to 80-90 degrees Celsius.

Cooling the solution to room temperature for crystallization.

Initiating crystallization with a glass rod.

Adding cold water to halt the reaction.

Using an ice water bath to ensure complete crystallization.

Vacuum filtration to collect aspirin crystals.

Rinsing the flask and filter paper with ethanol.

Recrystallization to purify the product.

Dissolving impure aspirin in ethanol.

Heating water and adding it to the crude sample.

Adding more solvent to dissolve the sample completely.

Recrystallizing by cooling the solution.

Using a vacuum system to dry the product.

Weighing the filter paper and watch glass for mass measurement.

Using iron(III) chloride for a qualitative assay.

Color change of iron(III) chloride in the presence of a phenol ring.

Testing the presence and purity of aspirin with iron(III) chloride.

Successful synthesis and purification of aspirin confirmed by the test.

Transcripts

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Related Tags
Organic SynthesisAspirin ProductionLab TechniquesChemistry TutorialAcetylsalicylic AcidSalicylic AcidRecrystallizationCrystallizationPharmacologyQualitative Assay