NUCLEOPHILIC ACYL SUBSTITUTION: THE SYNTHESIS OF ESTERS PRE-LAB

EXPERIMENT 13 NUCLEOPHILIC ACYL SUBSTITUTION: THE SYNTHESIS OF ESTERS I.

Objective(s) 1. To synthesize ester through a reversible acid-catalyzed reaction of a carboxylic acid with an alcohol 2. To verify experimentally the interconversion among acyl compounds.

II.

Schematic Diagram of Procedures

Flavor Banana

Alcohol 2-pentanol (0.06 mol)

Volume,mL 6.54 mL + 0.3mL

Acid Acetic acid (0.06 mol)

Volume,mL 3.43

Peach

Benzyl alcohol (0.04 mol)

4.14 mL + 0.3 mL

Acetic acid (0.04 mol)

2.29

Pear

1-propanol (0.09 mol)

6.74 mL + 0.3 mL

Acetic acid (0.09 mol)

5.15

Pineapple

Ethanol (0.09 mol)

5.25 mL + 0.3 mL

Butyric acid (0.09 mol)

8.28

Raspberry

2-butanol (0.08 mol)

7.36 mL + 0.3 mL

Formic acid (0.08 mol)

3.04

Materials and Apparatus 2-pentanol 1-propanol 2-butanol Benzyl alcohol Butyric acid NaHCO3 Glacial CH3COOH CH3CH2OH Formic acid

anhydrous Na2SO4 conc. H2SO4 separatory funnel (30 ml) Bunsen burner round bottom flask (25 ml0 boiling chips water condenser Formic acid

From the table, determine the quantity of alcohol and acid needed to prepare the ester.

Add boiling stones. Mix the reactants in a 25-mL round bottom flask.

(Do not use calcium carbonate (marble) boiling stones because it will dissolve in the acidic medium.)

Cool the mixture to room temperature.

Attach a reflux condenser and allow the mixture to reflux for 4560 minutes.

Carefully add 2-3 drops of concentrated H₂SO₄ while gently swirling.

Pour into a 30 mL separatory funnel.

Rinse the reaction flask with cold water and add the washings to the separatory funnel.

Repeat this until the aqueous layer is twice the volume of the organic layer.

Add saturated NaCl solution to hasten separation.

Shake and allow the layers to stratify.

Add solid NaHCO₃ until the acid is removed completely. (How do you know? Separate the layers.)

Add approximately 1.00g of anhydrous Na₂SO₄.

Determine the boiling point.

Weigh the ester and calculate the percentage yield.

If the mixture does not appear dry ( drying agent clumps in the mixture or does not "flow", cloudy solution or obvious drops of  water) transfer the ester to a dry and clean 25 mL Erlenmeyer flask.

Distill the ester using thoroughly dried glassware.

Add 0.5 g Na₂SO₄ to complete the drying.

Ensure that the crude ester is clear.

III.

Set-ups No set-ups used

IV.

Waste Disposal Aqueous solutions should be discarded by diluting with water first before pouring in the sink. Dispose the spent drying agent in the trash bin or you may dissolve it in water and flush it down the sink. Halogenated organic solvents are disposed into “halogenated solvent waste” jar.