Expt #2. Diels-Alder
Reaction of α-Phellandrene with Maleic Anhydride
Relevant textbook readings -
Smith 16.12-16.14 - 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, 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 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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