Lab Activity 15: Esters

Background:
An ester is an organic compound formed by the reaction of an alcohol with an organic acid. An ester will hydrolyze unless the water formed in the reaction is removed by dehydrating agent. In this investigation, you will use sulfuric acid as the dehydrating agent in the general reaction:

Where R represents an organic radical such as -CH3 or -C2H5. The -COOH group is the functional group of an organic acid. The -OH group is the functional group for alcohols.
Esters are useful as flavorings, aromatics, and solvents. The presence of an ester is often noticed by a characteristic odor that is different from either of the reactants. In this investigation, you will prepare several familiar esters and try to identify them by their odors.

Purpose:
To prepare several esters and observe the mechanism for their general reaction.

Materials:

CAUTION: DO NOT HEAT ORGANIC CHEMICALS DIRECTLY WITH THE BURNER FLAME. ALWAYS HEAT ORGANIC CHEMICALS IN A WATER BATH, SINCE MANY ORGANIC CHEMICALS ARE VOLATILE AND FLAMMABLE. WEAR SAFETY GLASSES AND AN APRON THROUGHOUT THIS INVESTIGATION.
	Figure 1: Setup

Procedures:

1. Fit a cork with a 60 cm piece of glass tubing. This tubing will serve as a condenser.
2. Set up a ring stand with ring and wire gauze. Half fill a 400-ml beaker with water and place it on the wire gauze. Immerse a 125-ml Erlenmeyer flask in the water bath and clamp it to the ring stand.
3. Add 5 ml of stock glacial acetic acid and 5 ml of methyl alcohol to the flask. Then add 4 drops of concentrated sulfuric acid. Stopper the flask with the cork you have fitted with the 60-cm piece of glass tubing (See figure 1). Clamp the tubing to the ring stand.
4. Heat the water bath slowly until the mixture in the flask is gently boiling. Make sure the heated reaction mixture does not rise above the end of the glass tubing and spurt out. Continue to heat the water bath for about 10 minutes.
5. Turn off the Bunsen burner and allow the mixture in the flask to cool. Remove the glass tubing and note what has happened in the flask. Cautiously smell the product of the reaction. Suggest a name for the ester that has been formed.
6. Clean the Erlenmeyer flask and repeat procedures 1-5 using 5 ml of amyl (n-pentyl) alcohol and 5 ml of glacial acetic acid. Remember to add 4 drops of concentrated sulfuric acid.
7. Clean the Erlenmeyer flask and repeat procedures 1-5 using 1 spatula full of salicylic acid crystals and 5 ml of methyl alcohol. Remember to add 4 drops of concentrated sulfuric acid.

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