SMELLY LAB
(Synthesis of an Ester)
Name______
Date______Period___
OBJECTIVE
Esters are a class of organic compounds known for their use in flavorings and perfumes. In this activity you will perform an organic synthesis to build an ester from the reaction of an alcohol and a carboxylic acid.
The general reaction that occurs when an alcohol and a carboxylic acid get together is show by the following equation:
This formation of the ester is called a condensation type reaction because a water molecule is kicked out when the alcohol and acid get together. The H2SO4 that is written above the arrow shows that it is a catalyst – it is there only to make the reaction happen faster, and is not changed during the reaction.
MATERIALS
250 or 400 mL Beaker Test tube Test tube tongs Hot plate Boiling chips
Alcohol and Acid pair for any reaction 1-7 of your choice Conc. H2SO4
PROCEDURE
1. Set up a water bath with a hot plate and your beaker filled about 3/4 full of water. Add a boiling chip to the beaker and heat the water
2. Choose one of the 7 reactions listed in the DATA / RESULTS section and place the required number of drops of the alcohol and acid (or scoop for the solid samples) into a clean, dry test tube.
3. Note the odor of the alcohol and the acid before you mix them in the test tube. DO NOT take a big whiff – waft the odor towards your nose. Some of these are very strong and will burn your nasal passages if inhaled directly.
4. IMPORTANT – come to your teacher and she will add 10 drops of Concentrated H2SO4 to your test tube.
5. Place your test tube in the water bath using test tube tongs. Use the tongs to move the test tube in a circle within the water bath. Continue heating in the boiling water bath for two minutes. The water bath should be boiling – not the solution in the test tube.
6. Remove the test tube from the water bath and note the odor.
7. If you have time – you may perform another experiment – otherwise – try to find another lab group that has made some of the other esters that you can smell.
8. WASH YOUR HANDS AND CLEAN UP YOUR MESS!! (Contents of test tubes may be discarded down the sink with plenty of water)
DATA / ANALYSIS
1 / Pentanol / 20 drops / acetic / 10 drops / Iso-amy acetate
2 / Ethanol / 20 drops / acetic / 10 drops / Ethyl acetate
3 / Methanol / 15 drops / salicylic / 1 scoop / Methyl salicylate
4 / n-butyl alcohol / 28 drops / acetic / 20 drops / N-butyl acetate
5 / Ethanol / 15 drops / propanoic / 20 drops / Ethyl propionate
6 / Ethanol / 20 drops / benzoic / 1 scoop / Ethyl benzoate
7 / Octanol / 20 drops / acetic / 10 drops / Octyl acetate
CONCLUSION / QUESTIONS
1. Fill out the chart above for the ODORS of as many reactions as possible.
2. Write the chemical equation for the reaction that your performed, using the example reaction show in the OBJECTIVE section as a guide.
3. How do you think your results may have been effected if you had an uneven ratio of molecules of alcohol to acid?
4. Classify each compound as a carboxylic acid, an alcohol, or an ester:
a. CH3CH2CH2CH2OH
b. CH3OCOCH2CH3
c.
d.