Fisher Esterification Lab

Introduction

• Objective: Overview of the Fisher esterification reaction and its mechanism, followed by the experimental procedure and characterization techniques.
• Reaction: Acetic acid reacts with isopentyl alcohol, catalyzed by sulfuric acid, to form isopentyl acetate (banana oil) and water.
• Mechanism: Involves activation of acetic acid by sulfuric acid, nucleophilic attack by alcohol, formation of a tetrahedral intermediate, and reformation of the carbonyl group.

Reaction and Mechanism

• Principle: Reaction is in equilibrium; removal of water drives the reaction towards product formation.
• Methods to Remove Water:
  • Use silica gel beads to absorb water.
  • Employ sulfuric acid as it is non-aqueous, unlike other acids that could introduce water.
  • Use a drying tube with calcium chloride to absorb atmospheric moisture.

Experimental Procedure

• Reflux Technique: Boil compounds to achieve activation energy while preventing loss via a water condenser.
• Setup:
  • Conical vial for reaction, attached to a water condenser.
  • Tubing for water flow, with cold water circulating to condense vapors.

Isolation and Purification

• Limiting Reagent: Identify isopentyl alcohol as the limiting reagent; acetic acid remains in excess.
• Product Isolation:
  • Use sodium bicarbonate to deprotonate and extract excess acetic acid into the aqueous layer.
  • Perform three washes to ensure removal of excess acid.
• Drying: Use sodium sulfate to absorb residual water, achieving a free-flowing organic phase.
• Distillation:
  • Separate products based on boiling points.
  • Measure boiling point (target ~142°C for isopentyl acetate).

Characterization Techniques

• Boiling Point Measurement: Validate product purity.
• Refractive Index: Compare with literature value (expected ~1.4000).
• Infrared Spectroscopy:
  • Analyze functional groups; identify contamination if present (e.g., OH peak indicating impurities).

Lab Preparation and Safety

• Materials: Lab coat, goggles, gloves, long pants, and closed-toed shoes.
• Storage: Lockers for personal items; secure lab equipment in drawers.
• Safety: Handle reagents with care, cap bottles, and respect shared resources.

Clean-Up and Disposal

• Waste Disposal:
  • Aqueous waste bucket for sodium bicarb rinses and water.
  • Organic waste bucket for leftover products and solvents.
  • Desiccant waste for calcium chloride, sodium sulfate, and silica gel beads.
• Glassware Cleaning: Use acetone, which dissolves organics and mixes with water.
• Return Equipment: Ensure surgical tubing and other materials are available for future use.