Docstoc

Chester the Ester

Document Sample
Chester the Ester Powered By Docstoc
					“Chester the Ester”:                                                     Name___________________________
                                                                         Date____________________________
A Chemistry Lesson on the Process of Ester Formation
Recently in Chemistry class we identified the esters as one of the families of organic compounds. Ester
compounds are familiar and beneficial in that esters are the chemical compounds responsible for many of the
pleasing scents of flowers and fruits. Manufactured synthetically, esters are used as artificial fruit essences
to provide fruity aromas for soaps, shampoos and perfumes, and to provide artificial flavors for such
essentials as banana runts and pineapple lifesavers. In this lab you will have the opportunity to create your
own artificial aromas by producing a variety of ester compounds.
Part I: The Chemistry of Esters
Esters are formed when an organic acid reacts chemically with an alcohol in the presence of heat and a
catalyst.

       Define the term “Catalyst”:


The catalyst in the esterification process is not a part of the chemical reaction, but provides a “kick” to help
the reaction happen. The definition of a catalyst suggests that it is not consumed nor significantly changed
during the reaction. Therefore, whatever compound you introduce as a catalyst at the beginning of a
chemical reaction will still be present after the reaction is complete.
Esters are formed when the OH group from the end of an alcohol molecule combines with the H from the
end of an organic acid molecule to form water. Water, however, is just a byproduct of the esterification
reaction. The main product, the ester, forms when the remainder of the organic acid molecule combines with
the remainder of the alcohol molecule, which will be an alkyl group of some kind.
Interestingly, many alcohols and most organic acids are known for their pungent, often nauseating odors.
Yet, when an alcohol and an organic acid react the result is an ester that has a very pleasing aroma. For
example, butyric acid (or butanoic acid), a four-carbon organic acid, has the distinct smell of sun-ripened
road kill. But when it is reacted with methyl alcohol the result is an ester (methyl butyrate, or methyl
butanoate) that is used for artificial fruit scents and flavors.
Part II: The Naming of Esters
Suppose we react propanoic acid with ethyl alcohol. First, draw a structural model of each of these
compounds in the space below:




Now, draw propanoic acid again, but leave of the terminal hydrogen atom (it becomes part of the water
byproduct of the reaction). Next, imagine removing the hydroxyl group (OH) from the ethyl alcohol
molecule. What alkyl group is left? Attach this alkyl group to the remainder of the propanoic acid molecule
to create the ester that forms from this reaction.
To name the ester remove the ic acid ending from propanoic acid and replace it with ate to get the second
word of the name. The first word is simply the name of alkyl group that came from the alcohol molecule.
Thus, the name of molecule produced by reacting propanoic acid with ethyl alcohol is Ethyl propanoate.

Part III: The making of Esters

   A) Ester Number 1
         1. In a test tube, combine 3 ml of acetic acid with 2 ml of ethyl alcohol. Carefully assess the
             odor of the mixture.
         2. Add 8-10 drops of sulfuric acid to the ingredients in the test tube.
         3. Heat the contents of the test tube carefully over an alcohol burner until it begins to boil. Be
             careful not to allow the contents of the test tube to boil over
         4. Allow the solution to boil for about 1 minute, and then reevaluate the odor of the test tube
             contents.

           a) Describe the odor of the test tube contents prior to heating.




           b) Describe the odor of the test tube contents after heating.




   B) Ester Number 2
         1. Place 1 gram of powdered salicylic acid in a test tube. Add 1 ml of methyl alcohol. Carefully
             assess the odor of the mixture.
         2. Add 8-10 drops of sulfuric acid to the ingredients in the test tube.
         3. Heat the contents of the test tube carefully over an alcohol burner until it begins to boil. Be
             careful not to allow the contents of the test tube to boil over
         4. Allow the solution to boil for about 1 minute, and then reevaluate the odor of the test tube
             contents.

           c) Describe the odor of the test tube contents prior to heating.




           b) Describe the odor of the test tube contents after heating.
   C) Ester Number 3
         1. In a test tube, combine 3 ml of acetic acid with 2 ml of amyl alcohol. Carefully assess the
             odor of the mixture.
         2. Add 8-10 drops of sulfuric acid to the ingredients in the test tube.
         3. Heat the contents of the test tube carefully over an alcohol burner until it begins to boil. Be
             careful not to allow the contents of the test tube to boil over
         4. Allow the solution to boil for about 1 minute, and then reevaluate the odor of the test tube
             contents.

          d) Describe the odor of the test tube contents prior to heating.




          b) Describe the odor of the test tube contents after heating.




Part IV: Structural models and formulas

   1. Draw structure models for the acids and alcohols in each of your experiments.
   2. Draw structural models for each of the esters formed in your experiments.




   3. Determine the name of each of the esters formed in your experiments.




Part V: Analysis Questions

   1. If you were to write the chemical equations for the reactions that occurred in this lab, you would not
      include sulfuric acid as part of the equation. Why not? Where is the sulfuric acid after the reactions
      are complete?




   2. Write the esterification equations for each of the reactions in this lab.
   3. Write the chemical equations for the following esterification reactions:

       Ethyl Alcohol {CH3CH2OH} reacted with Butyric Acid {CH3(CH2)2COOH



       Amyl Alcohol {CH3(CH2)4OH} reacted with Benzoic Acid {C6H5COOH}



       Methyl Alcohol {CH3OH} reacted with Methanioc Acid {HCOOH}




   4. Name and draw structure diagrams for the esters formed in each of the reactions in question 3. Using
      the Internet, see if you can determine which of these esters goes by the common name of “pineapple
      oil”.




BONUS: Using the tune from “Frosty the Snowman”, write a song titled “Chester the Ester”. For credit, the
lyrics of your song must accurately reflect the chemistry involved in the formation of esters.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:19
posted:8/18/2012
language:Latin
pages:5