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JoVE Lab Manual
Lab: Chemistry
Education
Esterification
 

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Learning Objectives

At the end of this lab, students should know...

What is the general structure of an ester?

An ester consists of a carbonyl with an alkyl or aryl group on one side and an oxygen bound to another alkyl or aryl group on the other side.

What effect does alkyl chain length and different groups have on a simple ester?

Simple esters, or those with short alkyl chains, have smells and flavors of fruits and flowers. The structure of the alkyl chain influences the smell of the ester. Changing the length or even the groups present in the simple ester can drastically change the scent produced by the ester.

How is an ester formed?

In general, an ester is made from an acid in which at least one hydroxyl group (OH) is converted into an oxygen that is bonded to either an alkyl or aryl group. Most esters are formed from the reaction of a carboxylic acid and an alcohol, though other forms of esters exist, such as the phosphodiesters that form the backbone of DNA.

What is Le Chatelier's principle, and how can it affect the percent yield of an ester?

Le Chatelier's principle states that an equilibrium reaction can be driven in one direction by changing the concentration, pressure, temperature, or volume of the reagents or products. With a 1:1 mixture of carboxylic acid and alcohol, the esterification reaction reaches equilibrium with about 70% yield of the ester. By increasing the concentration of one of the reactants, either the carboxylic acid or the alcohol, the esterification reaction can be driven to reach equilibrium with about 90% yield of the ester.

How does Fisher esterification produce an ester?

The acid catalyst protonates the carboxylic acid via the double-bonded oxygen. This leads to an electron-poor carbon. The oxygen from the alcohol acts as a nucleophile, bonding with this carbon and losing a hydrogen in the process. The acid catalyst once again protonates the intermediate product, resulting in a restructuring of the product, where a water molecule leaves and the carbonyl group reforms. Deprotonation occurs to produce the final neutral ester.

List of Materials

  • Lab stand
    5
  • 3-prong clamp
    10
  • Stirring hotplate 
    5
  • Lab jack
    5
  • Heating mantle with temperature controller
    5
  • Tubing for waterlines
    10
  • Joint clip
    5
  • Vacuum grease
    5 tubes
  • Lab wipes
    5 boxes
  • 10-mL glass graduated cylinder
    5
  • 600-mL glass beaker
    5
  • 50-mL glass round-bottom flask with cork holder
    5
  • Standard condenser
    5
  • Small stir bar
    5
  • Glass stirring rod
    5
  • Package of pH paper
    5
  • Pasteur pipette bulb
    10
  • Small glass funnel
    5
  • Filter paper
    20
  • Acetic acid
    20 mL
  • Butanoic acid
    30 mL
  • Anthranalic acid
    20 g
  • 1-propanol
    20 mL
  • Isoamyl alcohol
    30 mL
  • 1-octanol
    40 mL
  • 1-butanol
    30 mL
  • Ethanol
    20 mL
  • Methanol
    30 mL
  • 3 M sulfuric acid
    50 mL
  • Saturated sodium bicarbonate (9.3 - 9.6%)
    100 mL
  • Propyl acetate
    5 mL
  • Isoamyl actetate
    5 mL
  • Octyl acetate
    5 mL
  • Butyl acetate
    5 mL
  • Ethyl acetate
    5 mL
  • Methyl butyrate
    5 mL
  • Methyl anthranilate
    5 mL
  • 10-mL glass vial with solvent-resistant cap
    14
  • Analytical balance
    1
  • Weigh boats
    2
  • Spatula
    1
  • Paraffin film
    1 box
  • Scissors
    1
  • Pasteur pipettes
    Dependent on lab size
  • Crushed ice
    Dependent on lab size
  • Ice scoop
    Dependent on lab size
  • Insulated ice cooler
    Dependent on lab size

Lab Prep

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

  1. Preparation of the Laboratory

    Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

    • First, put on a lab coat, safety glasses, and nitrile gloves. Note: Some of the reagents are volatile or have unpleasant odors, so you will handle them in a fume hood.
    • Ensure that you have glass and organic waste containers and that each sink has paper towels.
    • Follow the table to designate codes for the carboxylic acids and alcohols used in this lab. The carboxylic acids are coded A through C, and the alcohols are coded D through I. The students will use a 3:1 molar ratio of alcohol to carboxylic acid in the reaction.
      Code Compound MW
      (g/mol)
      Density at RT (g/cm3) Moles per vial Grams per vial cm3 per vial Number of vials
      A Acetic acid 60.05 1.049 0.07 4.2035 4.0 3
      B Butyric acid 88.11 0.953 0.07 6.1677 6.5 3
      C Anthranilic acid 137.14 - 0.07 9.5998 - 1
      D 1-Propanol 60.10 0.803 0.21 12.6210 15.7 1
      E Isoamyl alcohol 88.15 0.810 0.21 18.512 22.8 1
      F 1-Butanol 74.12 0.810 0.21 15.565 19.2 1
      G Ethanol 46.07 0.789 0.21 9.6747 12.3 1
      H Methanol 32.04 0.791 0.21 6.7284 8.5 2
      I 1-Octanol 130.23 0.830 0.21 27.348 32.9 1
    • Prepare the three carboxylic acids: acetic acid, butyric acid, and anthranilic acid. Each group will need 0.07 moles of their assigned carboxylic acid in a vial.
    • Tare a 10-mL glass vial on an analytical balance in a fume hood. Use a Pasteur pipette to measure 4.2035 g of acetic acid, which will be about 4 mL. Cap the vial and label it ‘A’. Prepare two more labeled vials of acetic acid in the same way.
    • Weigh 6.1677 g of butyric acid, which will be about 6.5 mL, in a tared 10-mL vial. Cap the vial and label it ‘B’. Prepare two more vials of butyric acid in the same way.
    • Use a small spatula to weigh 9.5998 g of solid anthranilic acid in a tared 10-mL vial. Cap the vial and label it ‘C’. You should now have a total of seven vials of carboxylic acid.
    • Prepare the 7 alcohols. Each group will need 0.21 moles of their assigned alcohol in a vial. Use the table as a guide to prepare and label one vial of each alcohol. Prepare and label two vials of methanol.
    • You should now have a total of seven vials of alcohol. Keep the reagent vials in the instructor's hood for now and put away the stock bottles of the carboxylic acids and alcohols.
    • Assign each student group one of these seven combinations of reagents.
      Ester code Carboxylic acid Alcohol Ester product Scent
      AD Acetic acid 1-Propanol Propyl acetate Pear
      AE Acetic acid Isoamyl alcohol Isoamyl acetate Banana
      AI Acetic acid 1-Octanol Octyl acetate Orange
      BF Butyric acid 1-Butanol Butyl butyrate Pineapple
      BG Butyric acid Ethanol Ethyl butyrate Strawberry
      BH Butyric acid Methanol Methyl butyrate Apple
      CH Anthranilic acid Methanol Methyl anthranilate Grape
    • Prepare or obtain seven vials of the fruit scents and label them with the fruit names as references.
    • Set out the following glassware and equipment at each student lab station (we suggest that students work in pairs):
    • Put bottles of saturated sodium bicarbonate and 3 M sulfuric acid in a dedicated fume hood, along with a roll of plastic paraffin film and scissors.
    • Set out filter paper and Pasteur pipettes in a central area so that every student group can easily access them.
       1    Lab stand
       2    3-prong clamps
       1    Stir plate
       1    Lab jack
       1    Heating mantle
       1    Temperature controller
       2    Pieces of tubing (for condenser)
       1    Joint clip
       1    Tube of vacuum grease
       1    Box of laboratory wipes
       1    10-mL graduated cylinder
       1    600-mL beaker
       1    50-mL round-bottom flask and flask stand
       1    Standard condenser
       1    Small stir bar
       1    Glass rod
       1    Package of pH paper
       2    Pasteur pipette bulbs
    • Just before the lab, fill a large insulated cooler with crushed ice. Place the cooler and an ice scoop in a central area in the lab.
    • When the students arrive, show them how to safely waft vapors before giving them their assigned reagents.

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