Esters: The Secret of Natural and Synthetic Fragrances

Marianne Dlugo                 St. Cletus School
                               700 W. 55th Street
                               La Grange IL 60525
                               708-352-4820

Objectives:

1. To acquaint junior high students with the many natural foods and plants that
   contain an ester. 
2. To learn what an ester is in chemistry.
3. To learn how an ester is synthesized in the laboratory.
4. To learn how a scratch'n'sniff is encapsulated on a sticker.

Materials:

1. Alcohols, organic acids, sulfuric acid
2. Beaker for hot water bath
3. Test tube racks
4. Grease pencil for marking test tubes
5. Graduated cylinder and/or plastic syringe
6. Hot plate
7. Stirring rods
8. Gloves
9. Goggles
10. Pipet

Strategy:

1. To have students detect smells of known objects as they are displayed in a
   hidden form, covered with cheesecloth.
2. To show how some plants have a natural odor, eg., sweet alyssum, herbs, etc.
3. To explain what an ester is:
 organic acid + alcohol (using sulfuric acid as a catalyst) " ester + water
4. Have students make an ester by using fresh peas, brown sugar and some apple.
   This mixture, when blended together, will smell, but not taste, like 
   strawberries.
5. Now demonstrate how to make a synthetic ester in the lab using one of the 
   following formulas:
    
       acid                    alcohol           sulfuric acid     essence
1 gram salicyclic acid  2 mL methyl alcohol       8 -10 drops     wintergreen 
3 mL acetic acid        2 mL octyl alcohol       10 -15 drops     orange
4 mL formic acid        2 mL ethyl alcohol       20 drops         rum
2 mL butyric acid       2 mL ethyl alcohol       15 -20 drops     pineapple
2 mL butyric acid       2 mL methanol            15 -20 drops     apple
   
 
6. Prepare a hot water bath by filling 1/2 of a 400 mL beaker with water and,
   placing it on a hot plate, heat it to a point where it is slightly boiling.
7. Look at the formula of the acid-alcohol combination you are looking for.
8. Into that solution you are going to add the catalyst, sulphuric acid.
9. Then you will place the entire contents of the test tube into the hot water 
   bath for about one minute. 
10. Waft the odor and notice the essence.  Then place this essence in a small 
    amount of hot water.  This will help diffuse the odor throughout the room.
11. Each group will then proceed to make their own ester.
12. Following this, I will simulate how a scratch'n'sniff is made using bubble
    packaging material that has been injected with an ester.  I will break the
    bubbles and display the puddle explaining how the scent is released.
 
Performance assessment:

1. What essence have you made using the formula that was given?
  ________________________________________

2. What is the difference between a natural and a synthetic essence?
  ________________________________________

3. You have been named to the head of the perfume department at Marshall 
   Field's.  Among the numerous essences under your authority, the CEO has asked 
   that you assemble them according to natural and synthetic fragrances.  Since 
   many people today are going back to the natural, it is very important that 
   you do this correctly. 

   What factors would you use to assemble them in their proper section?       
   Name some of the products that can be placed under natural, then name some
   under synthetic.


Rubric:

6.  A student will successfully understand the difference between natural and 
    synthetic essences.  S/he will look at the labels and determine if there is
    an ingredient having an "yl" (for the alcohol ending) and an "ate" ending
    (for the acid).  Then they must have a synthetic fragrance.  They will 
    correctly place at least three different cosmetic/perfumes, etc.,  under
    natural and an equivalent number under the synthetic.

5.  A student will successfully understand the difference between natural and 
    synthetic essences.  They will understand the "yl" and "ate" ending.  They 
    will correctly place at least two different cosmetic/perfumes, etc., under 
    natural and an equivalent number under the synthetic.     

4.  A student will successfully understand the difference between natural and 
    synthetic essences.  They will understand the "yl" and "ate" ending.  They 
    will correctly place at least one different cosmetic/perfume, etc., under 
    the natural and another under the synthetic column.

3.  A student will successfully understand the difference between natural and 
    synthetic essences.  They will understand the "yl" and "ate" ending.

2.  The student will successfully understand the difference between natural and 
    synthetic essences, or the "yl" and the "ate" ending on the label being a
    synthetic ester.

1.  The students will successfully understand how to make an ester.

0.  The students will not have done the lab.