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Name: Esterification Lab Introduction Carboxylic acids and alcohols are often warmed together in the presence of a few drops of concentrated sulphuric acid in order to observe the smell of the esters formed. You would normally use small quantities of everything heated in a test tube stood in a hot water bath for a couple of minutes. Because the reactions are slow and reversible, you don't get a lot of ester produced in this time. The smell is often masked or distorted by the smell of the carboxylic acid. A simple way of detecting the smell of the ester is to pour the mixture into some water in a small beaker. Apart from the very small ones, esters are fairly insoluble in water and tend to form a thin layer on the surface. Excess acid and alcohol both dissolve and are tucked safely away under the ester layer. Small esters like ethyl ethanoate smell like typical organic solvents (ethyl ethanoate is a common solvent in, for example, glues). As the esters get bigger, the smells tend towards artificial fruit flavouring - "pear drops", for example. Safety Apparatus and chemicals: Careful this lab includes the use of strong acids like concentrated sulfuric acid. Everybody has to use lab goggles and be very careful!!! Smelling Chemicals: never smell chemicals by sticking your nose into a test tube. Esters and their reactants can damage your mucus membrane. Hold approx 5 inches from your face then fan with a hand over the test tube opening toward your nose. Materials: Each group lab apron eye protection 4 – 25x250mm test tubes 1 – 250ml beaker 2 – 50ml beakers Hot plate Thermometer Ring stand with clamp Communal (teacher monitored) dropper bottles filled with liquid carboxylic acids and alcohols Scoopula for solid chemicals Analytical balance Name: Procedure: 1. Set up a 250mL beaker on a hot plate, filling the beaker about 2/3 full of water. 2. Use a clamp to support a 18x150mm test tube. Lower the test tube into the water bath. 3. Check the odor of acetic acid and ethanol. WAFT! DON’T SNORT! 4. Put about 2mL of acetic acid into the supported test tube. 5. Add about 2mL of ethanol to the acid in the test tube. 6. Add about 10 drops of concentrated sulphuric acid catalyst to the mixture. CAUTION!!!-very corrosive! 7. Invert a beaker overtop the test tube. 8. Heat the water bath until the mixture in the test tube starts to bubble slowly. SLOWLY!!!!! 9. Allow the mixture to cool for several minutes.(5minutes) 10. Using a 50mL beaker, fill with 30mL of cold water. Pour test tube contents into this beaker 11. What smell did you get? 12. Repeat procedure 1 through 10 for your choice of making THREE more esters. The final esters are found below. ONLY ATTEMPT TO CREATE THE LISTED ESTERS. Others can be very strong. Any solid you are using, use 1.00g of it, other wise 2-3mL of liquid. 13. Dispose your ester down the drain with lots of water, wash with soap and dry. Results: 1. Complete the table below Reaction Alcohol Acid 1 Ethanol Acetic Acid (ethanoic acid) 2 3 4. Smell before Rx Smell after Rx Name: 2. Ester Names and formulas a. Draw the reactions for 1 - 4 and name the esters you formed. Name: Esterification Reactions Ester Structure Smell Ethyl methanoate (ethyl formate) Lemon, rum, strawberry Methyl ethanoate (methyl acetate) glue isopropyl ethanoate (isopropyl acetate) fruity Benzyl ethanoate (benzyl acetate) peaches Isopentyl ethanoate (isopentyl acetate or Isoamyl acetate) pear, banana (flavoring in Pear drops) Ethyl ethanoate polish remover, model glue octyl ethanoate fruity-orange Isobutyl propionate Rum Methyl propanoate fruity Methyl butanoate pineapple, apple, strawberry Ethyl butanoate banana, pineapple, strawberry Benzyl butanoate Fruity, plum Ethyl pentanoate apples Methyl salicylate (Methyl-2-hydroxybenzoate) root beer, wintergreen, Germolene Methyl benzoate fruity, ylang ylang, feijoa Name: Name: Teacher Copy: Esterification Reactions Alcohol ethanol Carboxylic Acid methanoic acid (Formic acid ) Ester Ethyl methanoate (ethyl formate) Structure Smell Lemon, rum, strawberry methanol Methyl ethanoate glue Isopropyl alcohol isopropyl ethanoate fruity Benzyl alcohol Benzyl ethanoate peaches Isoamyl alcohol (Isopentyl alcohol) ethanoic acid (Acetic acid) Isoamyl ethanoate pear, banana (flavoring in Pear drops) nail polish remover, model paint, model airplane glue ethanol Ethyl ethanoate octanol Octyl ethanoate fruity-orange Isobutyl alcohol Isobutyl propionate Rum methanol Methyl propanoate fruity methanol Methyl butanoate Propanoic acid ethanol Benzyl alcohol STRONG SMELL Butanoic acid (butyric acid) Ethyl butanoate pineapple, apple, strawberry banana, pineapple, strawberry Benzyl butanoate Fruity, plum apples Modern root beer, wintergreen, Germolene and Ralgex ointments (UK) ethanol Pentanoic acid Ethyl pentanoate methanol Salicylic acid (2-hydroxybenzoic acid) Methyl salicylate (Methyl-2hydroxybenzoate) methanol Benzoic acid Methyl benzoate fruity, ylang ylang, feijoa Name: