Preparation of an Ester
Name ______Period ______
PREPARATION OF AN ESTER
Objective/Purpose: to produce an ester (methyl salicylate) and to identify its characteristic odor
Introduction: Many natural and artificial flavorings belong to a class of compounds called esters. An ester is formed when a carboxylic acid reacts with an alcohol in a process known as esterification.
The general reaction is shown below:
In this reaction, a hydrogen from the acid combines with the hydroxide (-OH) from the alcohol to form water. In order to speed up the process, you will add concentrated sulfuric acid, which acts as a dehydrating agent.
Safety Precautions:
• You MUST wear safety goggles at all times.
• Concentrated sulfuric acid is extremely corrosive. Use caution when handling any solutions containing this chemical. If you get sulfuric acid on your skin, wash the area immediately and notify your teacher.
• Organic alcohols are flammable. Keep them away from all open flames and make sure your hotplates are turned off before starting the reaction.
• When smelling esters, do not “sniff” them directly from the flask. Using your hand, waft the odor gently towards your nose.
Materials
100 mL beaker, 125 mL Erlenmeyer flask, Small test tube, Test tube holder, Thermometer,
Safety Goggles
Procedure:
1. Add about 50 mL of tap water to a 100 mL beaker. Heat the water on a hot plate until it reaches 90ºC. Then, turn off the hot plate.
2. Add 0.1 grams of salicylic acid to a clean, dry test tube. Then add 10 drops of methanol.
3. Add 2 drops of concentrated sulfuric acid to your test tube. Be VERY careful!
4. Using a test tube holder, place the test tube in the warm water and gently swirl for 5 minutes. Do not allow the contents of the test tube to bubble over!
5. Add approximately 50 mL of tap water to a small Erlenmeyer flask. Pour the contents of the test tube into the flask and swirl gently.
6. Carefully smell the ester by wafting the vapor towards your nose. Describe the odor of the sample and record your observations.
7. To clean up, pour the contents of your flask into the designated waste container (NOT down the drain!), wash the test tube, and wipe down your lab bench.
Observations:
Lab Questions:
1. What flavoring agent was produced in this reaction? In what type(s) of products would you expect to find methyl salicylate?
2. Using the information on page 1, write the chemical reaction for the formation of methyl
salicylate. The structures of salicylic acid and methanol are given below.
3. Explain why the reaction performed in this experiment is known as a dehydration reaction.