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Chapter 40

Chapter 40 Esterification. Synthesis of n -Butyl Ester of Unknown Acid by Azeotropic Distillation of Water. Purpose. In this experiment an Unknown carboxylic acid is esterified with butanol in the presence of an acid catalyst in an azeotropic distillation mode. The product is isolated by:

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Chapter 40

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  1. Chapter 40 Esterification. Synthesis of n-Butyl Ester of Unknown Acid by Azeotropic Distillation of Water

  2. Purpose • In this experiment an Unknown carboxylic acid is esterified with butanol in the presence of an acid catalyst in an azeotropic distillation mode. • The product is isolated by: • withdrawing the reaction mixture from reaction flask with a Pasteur pipette to leave the catalyst behind and • extraction with aqueous NaHCO3 solution and ether.

  3. Reaction Mechanism • The mechanism involves initial protonation of CO2H group, attack of the nucleophilic OH, a proton transfer, and loss of H2O followed by loss of the catalyzing proton to give an ester.

  4. Comments • Follow pp. 559-560 (microscale). • Follow the lab handout for all experimental procedures. • Unreacted acid should be removed by washing reaction mixture with aqueous NaHCO3 with following extraction. • Perform IR and GC/MS analysis of the product. Prepare sample for NMR. • Determine the structure of the Unknown acid from spectral data. • Calculate yield. High to moderate yields should be achieved.

  5. Safety • Flammable reagents are used in this experiment, keep away from open flame. • Acids are corrosive, avoid contact with skin and eyes. • Caution: Note ‘fruity’ fragrance of the final product (use wafting, do not inhale!). n-Butyl acetate can cause irritation of eyes, upper respiratory system and skin.Potential symptoms of overexposure are headache, drowsiness, narcosis. Do not inhale, avoid contact with skin and eyes.

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