Expt #4. Diels-Alder
Reaction of α-Phellandrene with Maleic Anhydride
Relevant textbook readings -
Klein - chapter 17.6-17.8. Mohrig - chapter
15.
Literature Reference - Stockmann,
H. J. Org. Chem. 1961 26, 2025-2029
Prelab - Make sure you
calculate the volume of phellandrene and the mass of
maleic anhydride to use and include both in your table
of reactants and products. Also make sure to include the
theoretical yield of the product.
Overview - You will carry
out the Diels-Alder reaction of the terpene natural
product, (R)-(–)-α-Phellandrene, with Maleic
Anhydride. The resulting product could conceivably be
any of four possible diastereomers, however, the
configuration of C-5 of the phellandrene must be
retained as shown in equation 1.
![](phellandrene%20DA%20rxn.gif)
We will run the reaction and obtain
a crystalline product that will be thoroughly
characterized by
1H, 13C,
DEPT, COSY, HMQC, and HMBC NMR. An IR spectrum (to
verify the presence of both anhydride and alkene
functional groups) and a mp will also be obtained (lit
mp 126° C).
Procedure
Reaction:
- In a 25-mL round-bottom flask
put 0.010 mole of maleic anhydride and 0.010 mole of
α-phellandrene.
- Add 5 mL of ethyl acetate,
attach a reflux condenser, and heat at reflux for 30
min.
- Allow to cool slowly to room
temperature then cool on an ice bath to maximize
crystal formation.
- Collect the crude product by
vacuum filtration.
Purification:
- Recrystallize the product from
ethyl acetate. (Review chapter 15 in Mohrig).
- Get the crystals as dry as
possible by sucking air through on the Buchner funnel
for approx 15 minutes or by air drying for one week.
Analysis:
- Obtain the IR spectrum using the
cast-film method of sample preparation. (see pp
286-287 in Mohrig).
- Prepare a sample for NMR
spectroscopy using acetone-d6 as the solvent, then obtain
a proton NMR. Do not clean out the NMR tube until you
know it isn't needed for additional spectra (see #3 below).
When you do clean the tube make sure to rinse it out
very thoroughly with acetone so that this product does
not remain as a contaminant and show up in the spectra
for future experiments.
- The group with the highest
quality proton NMR (as judged by the instructor) will
also obtain the following spectra: 13C
NMR, DEPT-135, HMQC, HMBC, or COSY. The instructor
will assist and the other groups will report on their
own proton NMR in conjunction with the additional
spectra from the chosen group.
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