1. Module 6

1.21. Page 3

Module 6 Lesson 4

Module 6—Petrochemicals

Module 6: Lesson 4 Lab—Synthesizing Esters

 

Purpose

 

You will prepare a synthetic, organic compound—an ester.

 

Retrieve your copy of the Module 6: Lesson 4 Assignment that you saved to your computer earlier in this lesson. Then, open the handout “Making Esters.” Complete the Pre-Lab question on the Assignment.

 

Materials

  • tap water
  • beaker
  • 25 mm × 250 mm test tubes (or larger) (one for each reaction)
  • three 10-mL graduated cylinders
  • test-tube clamp (or utility clamp)
  • reflux apparatus (one-hole stopper with inserted glass tubing)
  • alcohols and carboxylic acids made available by your teacher
  • dropper bottle containing concentrated sulfuric acid (handled only by your teacher)
  • weighing boat
  • lab stand
  • hot plate
  • thermometer
  • thermometer clamp
  • laboratory tongs
  • laboratory scoop
  • electronic balance
  • a vial of salicylic acid
  • evaporating dish (one per reaction)
  • test-tube rack
  • tray or large beaker containing ice

If you have access to the materials listed, you may be able to perform this investigation.

 

If you do not have access to these materials and a supervised laboratory, or if you would like to see the lab performed before you attempt it, view the virtual investigation “Lesson 4 Lab: Synthesizing Esters.” If you will not be completing the lab yourself, remember to record data and observations as you view the presentation.



 

Procedure

 

Step 1: Assemble a water bath by placing a 250-mL beaker, half-filled with tap water, onto the hot plate. Place the water bath close to the lab stand. Attach the thermometer clamp to the lab stand, and position the thermometer inside the clamp in such a way that it measures the temperature of the water inside the water bath. Attach the test-tube clamp to the lab stand.

 

Step 2: Transfer approximately 4 mL of the carboxylic acid you have chosen and approximately 5 mL of the alcohol you have selected into separate graduated cylinders. If you use salicylic acid, measure approximately 2 g of the salicylic acid crystals into a weighing boat.

 

Step 3: Transfer the contents from the graduated cylinders to the test tube. Fasten the test tube to the test-tube clamp attached to the lab stand in such a way that the reactants in the test tube are below the surface of the water bath.

 

Step 4: Use a clean graduated cylinder to measure 2 mL of concentrated sulphuric acid. Add this to the contents of the test tube.

 

Step 5: Attach the reflux apparatus to the test tube. Turn on the hot plate, and begin heating the water bath. Monitor the temperature of the water bath during the experiment to maintain the temperature of the water bath between 70 °C and 80 °C. Allow the contents of the test tube to heat for 15 minutes.

 

Step 6: Remove the test tube from the water bath, and allow the contents to cool for five minutes; then place the test tube into a second water bath containing cold or ice water for five minutes.

 

Step 7: Pour the cooled contents into an evaporating dish. Gently waft the vapour from the dish containing the synthesized ester toward you. Record the odour detected in the appropriate place in your table.

 

Step 8: Repeat Steps 2 to 7 for your two other esters.

 

Step 9: Follow your teacher’s instructions regarding the disposal of liquid waste. Be careful not to spill or splash the esters—these mixtures contain sulfuric acid.

 

Step 10: Disassemble, wash (if needed), and return the equipment to its appropriate place.

 

Module 6: Lesson 4 Assignment

 

If you have not already done so, retrieve your copy of the Module 6: Lesson 4 Assignment that you saved to your computer earlier in this lesson. Complete the remainder of the Assignment and save it in your course folder. You will receive instructions later in this lesson on when to submit your completed Assignment to your teacher.