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Making Scents of Esters Introduction: An ester is an organic compound that is formed, in addition to water, when a carboxylic acid reacts with an alcohol. This process is called esterification. General Reaction: Specific Reaction: Esterification typically requires a catalyst to speed it, and for decades, concentrated sulfuric acid (18M H2SO4) has been used to do so. Sulfuric acid is a very dangerous chemical, which can cause severe chemical burns when in contact with skin, and therefore, the utmost care should be taken when working with sulfuric acid. When carboxylic acids are esterified (combined with an alcohol to form an ester), the resulting esters are liquids with fruity flavors. These synthetic esters are used in the food industry as flavorings. In many cases, the synthetic esters produced in the laboratory are nearly the same molecules that give fruits their characteristic flavors. Materials: 4 small test tubes 400-mL beaker 4 125-mL Erlenmeyer flasks hot plate test tube holder goggles apron 4 alcohol/carboxylic acids pairs concentrated sulfuric acid (18M H2SO4) Procedure: *Record all data in the attached data table. 1. Add about 200 mL water to the 400-mL beaker. Heat the water until it boils and then turn off the hot plate. 2. Add 10 drops iosamyl alcohol to a clean, dry test tube. Label the test tube “1.” 3. Add 10 drops octyl alcohol to a second clean, dry test tube. Label the test tube “2.” 4. Add 20 drops methyl alcohol to a third clean, dry test tube. Label the test tube “3.” 5. Add 10 drops propyl alcohol to a fourth clean, dry test tube. Label the test tube “4.” 6. To test tubes 1, 2, and 4, add 30 drops acetic acid. 7. To test tube 3, add 0.5g salicylic acid. Gently swirl the test tube to ensure the salicylic acid to go into solution. 8. Add 2 drops of the concentrated sulfuric acid to each of the 4 test tubes. 9. Using a test tube holder, place the test tubes into the beaker of near-boiling water. Let the test tubes stand in the hot-water bath for 5 minutes. 10. Label the 125-mL Erlenmeyer flasks “1,” “2,” “3,” and “4.” Add water to each until it is about 1/3 full. 11. Pour the contents of the test tubes into the correctly labeled flask and swirl. 12. Carefully smell the ester by waving a hand across the mouth of the flask to push the vapor toward your nose. Describe the odor of the sample in the table below. 13. Rinse the contents of the flasks down the drain with water. Table 1: Alcohol/Carboxylic Acid Pairs and Resulting Esters Test Carboxylic Tube Alcohol Amount Acid Amount Ester Produced Odor of Ester 1 2 3 4 Questions: 1. Write the chemical reactions for each of the esters produced in the above procedures. 2. Isoamyl alcohol, octanol, methanol, and propanol contain what functional group characteristic of all alcohols? 3. Acetic acid and salicylic acid contain what functional group characteristic of all carboxylic acids? 4. The esters produced in this laboratory experiment contain what functional group characteristic of all ester? 5. Isobutyl alcohol and formic acid combine to produce a raspberry odor. Predict the name of the ester. Organic Structures: Alcohols: HO OH isoamyl alcohol methanol (or methyl alcohol) HO HO propanol octanol (or octyl alcohol) (or propyl alcohol) Carboxylic Acids: HO HO HO O O salicylic acid acetic acid Esters: HO O O O O methyl salicylate isoamyl acetate O O octyl acetate O O propyl acetate