Chem 102b Experiment 14: Part II Revised Preparation of Esters

Fischer esterification yields equilibrium between the reactants and products. As Le Chateliers
principle states, the equilibrium system will adjust to minimize any stress applied to the system.
If the concentration of either of the reactants is increased or if the concentration of either of the
products (i.e. carboxylic acid and ester) is decreased, the reaction will "shift to the right." Thus,
the yield of the products will be increased. Anhydrous sodium sulfate is a drying agent that
absorbs water. If anhydrous sodium sulfate were added to the product collection flask, water
would be removed and the reaction would be shifted to the right. The yield of the ester would
increase.
The experiment is to be performed by a group of 4 students. Each member of the group will
make, isolate, and characterize one of the esters listed below using the Fischer esterification
techniques. The product will be a liquid that will be purified via a two-step process. Purity of the
product will be determined using Fourier Transform Infrared absorption Spectroscopy.
Ester Alcohol Acid Boiling Point
Ethyl Acetate Ethanol Acetic Acid 77 C
Benzyl Acetate Benzyl Alcohol Acetic Acid 213 C
Isopentyl Acetate Isopentanol Acetic Acid 142 C
Octyl Acetate Octanol Acetic Acid 199 C
IR spectra will be collected for each of the esters synthesized and compared within each group.
IR spectra are specific for every compound and can be considered to be a kind of "fingerprint"
for that compound. As you learned in the qualitative analysis experiment, compounds that share
the same functional groups share some of the same properties. After the esters have been
synthesized and characterized, the groups should compare boiling points and IRs of the products.
You will be given spectra of the reactants. Please compare your analysis to the IRs of the
reactants and make some assessments about the completion of your reaction. Please note that
only the alcohol used to make the ester has changed. Consequently, the spectra for all the esters
will have many similaritiestake care to note the differences.
Glassware:
You will need to check out a macrokit from the preproom. In the macrokit there will be 2 round
bottom flasks (a 250-mL and a 100 mL); a condenser, a vacuum adapter, a distillation adapter,
and a thermometer adapter. You will also need 2 lengths of tygon tubing per student and a
mercury thermometer that will measure about 400 C. Taped to the inside of the macrokit lid is a
list of glassware that should be in the kit. Please make certain all items are there and are not
broken. The kits cost approximately $65.00 apiece. You need to be very cautious with this
glassware.