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

C: The Distillation
1. Transfer the dry ester to the round bottom flask and assemble a distillation apparatus.
Remember to clamp the round bottom flask, the condenser, and the vacuum adapter to a
ring stand. When inserting the thermometer into the thermometer adapter, use extreme
caution. The position of the thermometer needs to be at the "y" junction of the distilling
adapter to correctly determine the boiling point of the ester.
2. Use a clean 250-mL round bottom flask (which is clamped to ringstand) to receive the
distillate.
3. Have your instructor check your setup before proceeding.
4. Raise the sandbath/hotplate (seated on a ring that is clamped to a ringstand) to the
reaction flask. Be certain to cover the lower 1/3 of the reaction flask with sand.
5. Turn the hotplate on high. Make a note of your esters boiling point. When you are
within 20 degrees of your bp, lower the heat to a moderate heating level. Record
temperature every minute and make observations in your lab notebook.
6. Note the temperature when material begins to come out of the adapter. Note the
temperature again when it stops coming out. This is your boiling point range for your
ester.
7. The material you have collected should be your pure ester. You will take an IR spectra of
this material. Please label your flask according. Note the smell of your groups esters in
your lab notebook.
D: Infrared Spectroscopy
1. Check out an IR card from the 3 South preproom window.
2. Your instructor will demonstrate how to run a background on the instrument.
3. Using a micropipet, place 1-2 drops of your ester onto the cards surface.
4. Run a spectrum of your ester.
5. Print the spectrum.
6. You will have IRs of the starting materials: ethanol, benzyl alcohol, isopentanol, octanol,
and acetic acid.
7. Compare the IR of your ester with the starting materials and the other esters in your
group. Which peaks are shared; which peaks are unique to your spectra; do you have any
starting materials in your sample; do you have any water in your sample? Remember that
it is not efficient or effective to try to identify all the peaks of the spectrum. The peaks
that should interest you most are at Ester--1735 cm -1 (C=O)strong absorption, 1280-
1050 cm -1 (C-O) usually gives two or more absorptions with one stronger than the others
do. Acetic Acid will have a very broad O-H peak at 3300-2500 cm -1 , the C=O peak will
be a broad stretch at 1730-1700 cm -1 , and the C-O peak will be strong in the 1320-1210
cm -1 range.