Pharmaceutical Organic Chemistry 2024-2025

Pharmaceutical Organic Chemistry 2024-2025

• Course covers calculation of yield of reactions, atom economy, and practical work.

Calculation of Yield of Reaction

• Yield: The amount of product obtained in a chemical reaction.
• Actual yield: The measured amount of product.
• Theoretical yield: The maximum amount of product that can be obtained from the complete conversion of the limiting reagent.
• Limiting reagent (reactant): The reactant with the fewest moles, which limits the reaction.
• Ideal/Theoretical Yield: 100%

Calculation of Yield of Reaction

• Yield Percentage (relative yield): Measures the effectiveness of a synthesis.
• Theoretical Yield Calculation: no. of moles of limiting factor x molecular wt of product.
• Yield Percentage Calculation: (Actual yield / Theoretical yield) x 100%

Classifying Reaction Yields

• Quantitative: Yields around 100%.
• Excellent: Yields above 90%.
• Very Good: Yields above 80%.
• Good: Yields above 70-60%.
• Fair: Yields below 50%.
• Poor: Yields below 40%.

Atom Economy

• Definition: A measure of the efficiency of a chemical reaction. It's calculated by dividing the total number of atoms in the desired product by the total number of atoms in all reactants.
• Calculation: (Mass of Product / Mass of Reactants) x 100%
• Importance: Helps choose the most efficient reactions, reducing waste and maximizing desired product. If two reactions produce the same product, the one with higher atom economy is more efficient.

Atom Economy in Aspirin Synthesis

• Different acylating agents (acetyl chloride, acetic anhydride, acetic acid) have different atom economies for aspirin synthesis.
• Acetic acid has the highest atom economy (95.47%).

Reaction Efficiency

• Definition: Measures the mass of reactant atoms in the final product.
• Calculation: % yield x atom economy
• Green chemistry goal: Design synthetic pathways that improve both atom economy and yield to minimize waste.

Example 1: Ethyl Acetate Synthesis

• Reactants: 120 g of acetic acid and 230 g of ethanol.
• Product: 132 g of ethyl acetate.
• Calculations: Include steps to calculate molecular weights, moles, limiting reagent, theoretical yield, yield %, and reaction efficiency.

Practical Work: Liberation of Acid from Salt (Sodium Benzoate)

• Reaction: Sodium benzoate + HCl → Benzoic acid + NaCl
• Purpose: Demonstrates the liberation of benzoic acid from its salt form. Used as an antifungal preservative and test for liver function.
• Procedure:
  1. Dissolve sodium benzoate in water.
  2. Add HCl dropwise until precipitation occurs.
  3. Filter the precipitate.
  4. Recrystallize the benzoic acid.
• Materials: 1 g of sodium benzoate, 5 mL of water, 2.5 mL of 3N HCl, small beakers, filtration apparatus, and hot water.

Tools

• 2 small beakers
• Conical flask
• Watch glass
• Funnel
• 2 filter papers
• Dropper
• Lab coat
• Eye goggles
• Towel
• Holder

This quiz covers the calculation of yields in organic chemistry reactions, including actual yield, theoretical yield, and the concept of limiting reagents. Test your understanding of yield percentages and their classification. Perfect for students in a pharmaceutical organic chemistry course.