What is Acetylsalicylic Acid (Aspirin)?
The concept of acetylsalicylic acid (aspirin) is essential in chemistry and helps students understand various practical and theoretical applications related to this topic.
What is Acetylsalicylic Acid (Aspirin) in Chemistry?
Acetylsalicylic acid (aspirin) is an organic compound classified as an NSAID (nonsteroidal anti-inflammatory drug). This concept appears in chapters related to pharmaceutical chemistry, functional groups, and esterification reactions, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formula of acetylsalicylic acid is C9H8O4. It consists of a benzene ring, an acetyl group (COCH3), and a carboxylic acid group (COOH), and is categorized under aromatic carboxylic acids and esters. Its IUPAC name is 2-acetoxybenzoic acid.
Preparation and Synthesis Methods
Acetylsalicylic acid (aspirin) is commonly synthesized through the esterification of salicylic acid with acetic anhydride. This process is widely demonstrated in chemistry labs as well as used industrially. Sulfuric acid or phosphoric acid often acts as the catalyst. Here is a simplified reaction:
Salicylic acid + Acetic anhydride → Acetylsalicylic acid + Acetic acid
This method highlights the core principles of esterification—a very important reaction in organic chemistry.
Physical Properties of Acetylsalicylic Acid (Aspirin)
Acetylsalicylic acid is a white crystalline solid at room temperature. Key physical properties include:
- Melting point: 136 °C
- Boiling point: 140 °C (decomposes)
- Density: 1.40 g/cm3
- Molar mass: 180.16 g/mol
- Solubility in water: ~3 g/L (greater in organic solvents)
- Odor: Vinegar-like (in moist air due to hydrolysis)
- Weakly acidic (acid dissociation constant pKa ≈ 3.5 at 25 °C)
Chemical Properties and Reactions
Aspirin reacts as a typical ester and weak acid:
- Hydrolyzes in moist air to form salicylic acid and acetic acid
- Decomposes in basic solutions such as alkali metal hydroxides
- Forms salts with bases (sodium acetylsalicylate)
- Participates in aromatic reactions due to the benzene ring
- May explode when dispersed in air as a powder (rare in lab settings)
For more on these types of properties, see Carboxylic Acid Properties.
Uses of Acetylsalicylic Acid (Aspirin) in Real Life
Acetylsalicylic acid is widely used in everyday life and industry:
- Medicine: Pain relief, reducing fever, anti-inflammatory action, blood-thinning after surgery or for cardiovascular risk
- Lab: Analytical sample for testing carboxylic acids or esters, classic synthesis experiment
- Found in products like headache tablets (e.g., 75 mg or 81 mg “baby aspirin” doses for heart health)
- Occasionally studied for its cancer risk reduction and potential neuroprotective effects
To deepen understanding of how functional groups yield these uses, see Functional Group.
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with acetylsalicylic acid, as it often features in questions about organic synthesis, reaction mechanisms, functional group identification, properties, or applications in medical chemistry. Knowing its reactions and differences from salicylic acid or paracetamol is especially important for exam MCQs and short answer sections.
Relation with Other Chemistry Concepts
Acetylsalicylic acid is closely related to topics such as esterification (its synthesis), functional group (acetyl and carboxylic acid), and ester vs ether (for revision of classifications). These connections help students see the pathways from fundamental reactions to real-life drug chemistry.
Step-by-Step Reaction Example
1. Set up the reaction: Mix salicylic acid and acetic anhydride in a flask.2. Add a few drops of sulfuric acid (catalyst) and gently heat the mixture.
3. The hydroxyl (-OH) group of salicylic acid combines with the acetyl group, forming acetylsalicylic acid and releasing acetic acid.
4. cool, add water to decompose excess acetic anhydride, then filter the white crystals (aspirin) that form.
5. Final reaction: C7H6O3 + (CH3CO)2O → C9H8O4 + CH3COOH
Lab Tip or Classroom Mnemonic
Remember acetylsalicylic acid as “aspirin = acetyl group + salicylic acid.” Vedantu educators often use the phrase “pain-relieving ester” to highlight its structure and function together, making it easier for students to recall during quick revision sessions.
Try This Yourself
- Write the IUPAC name of acetylsalicylic acid.
- Identify if acetylsalicylic acid is acidic or basic in aqueous solution.
- Give two real-life examples of acetylsalicylic acid usage.
We explored acetylsalicylic acid (aspirin)—its structure, properties, reactions, and real-life importance. For more in-depth explanations and exam-prep tips, explore live classes and notes on Vedantu.
FAQs on Acetylsalicylic Acid (Aspirin): Structure, Synthesis, and Uses
1. What is Acetylsalicylic Acid or Aspirin - Formula and Structure?
Acetylsalicylic acid, commonly known as aspirin, is a widely used medication. Its chemical formula is C9H8O4. Its structure features a benzene ring with both an acetyl and a carboxylic acid group attached. This structure is crucial to its function as a nonsteroidal anti-inflammatory drug (NSAID).
2. What are the uses of Acetylsalicylic Acid or Aspirin?
Aspirin has several key medical uses:
- Pain relief (analgesic): Effective for headaches, muscle aches, and other types of pain.
- Fever reduction (antipyretic): Helps lower body temperature during illness.
- Inflammation reduction (anti-inflammatory): Reduces swelling and inflammation associated with conditions like arthritis.
- Cardiovascular protection: Inhibits platelet aggregation, reducing the risk of blood clots and heart attacks (often prescribed at low doses for this purpose).
The specific dosage and use depend on the individual's condition and doctor's advice.
3. What are the properties and side effects of Acetylsalicylic Acid or Aspirin?
Acetylsalicylic acid is a white, crystalline solid at room temperature. Key properties include a melting point of 135-136°C and weak acidity. However, it's essential to be aware of potential side effects:
- Gastrointestinal distress: Stomach upset, heartburn, nausea.
- Bleeding risk: Aspirin thins the blood, increasing the risk of bleeding or bruising.
- Allergic reactions: Some individuals experience allergic reactions, ranging from mild rashes to severe anaphylaxis.
- Reye's syndrome: Aspirin should not be given to children or teenagers with viral infections due to the risk of this rare but serious condition.
Always follow the recommended dosage and consult a doctor if you experience adverse effects.
4. How is acetylsalicylic acid synthesized?
Acetylsalicylic acid is synthesized through esterification. Salicylic acid reacts with acetic anhydride in the presence of an acid catalyst (like sulfuric acid) to produce aspirin and acetic acid. This reaction is a common organic chemistry laboratory experiment.
5. What is the difference between acetylsalicylic acid and salicylic acid?
Acetylsalicylic acid (aspirin) is a derivative of salicylic acid. The key difference is the presence of an acetyl group (-COCH3) in aspirin. This acetyl group modifies the properties of salicylic acid, making aspirin less irritating to the stomach and a more suitable oral medication.
6. Why should acetylsalicylic acid not be given to children with viral infections?
There is a strong association between aspirin use and Reye's syndrome in children and teenagers recovering from viral infections. Reye's syndrome is a rare but serious condition that can cause liver and brain damage. Therefore, alternative medications like acetaminophen are recommended for children and adolescents with viral illnesses.
7. What is the mechanism of action of aspirin?
Aspirin inhibits the cyclooxygenase (COX) enzymes. COX enzymes are involved in the production of prostaglandins, which mediate pain, fever, and inflammation. By blocking COX, aspirin reduces these effects.
8. How is acetylsalicylic acid metabolized and excreted?
Aspirin is rapidly absorbed from the gastrointestinal tract. It's then hydrolyzed to salicylic acid and acetic acid in the body. Salicylic acid is further metabolized in the liver and excreted primarily via the kidneys.
9. What are some common brand names for acetylsalicylic acid?
While acetylsalicylic acid is the generic name, many brand names exist, such as Bayer Aspirin, Bufferin, and others. The specific brand name doesn't affect the chemical composition of the drug itself.
10. What is the recommended dosage of aspirin?
The appropriate dosage of aspirin varies greatly depending on the reason for use (pain relief, fever reduction, cardiovascular protection). It's crucial to follow the instructions on the medication label or your doctor’s prescribed dosage. Never exceed the recommended dosage.
11. What happens in an aspirin overdose?
Aspirin overdose can be very dangerous and lead to serious complications, including tinnitus (ringing in the ears), respiratory problems, and metabolic acidosis. Seek immediate medical attention if an overdose is suspected.
