Expt #2. Diels-Alder Reaction of
α-Phellandrene with Maleic Anhydride
Relevant textbook readings -
Klein - chapter 17.7. 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, and HMQC NMR. An IR spectrum and mp will also be
obtained (lit mp 126-127).
Procedure
Reaction:
- In a 25-mL round-bottom flask put 0.010 mole of maleic
anhydride and 0.010 mole of α-phellandrene.
- Add 3.5 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.
- Save a small sample of the crude product for a mp
determination.
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).
- Obtain the mp of both the crude and recrystallized
product.
- Prepare a sample for NMR spectroscopy using acetone-d6
as solvent and obtain a proton NMR. 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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