Diels Alder Discussion: Experiment 13

The purpose of this experiment was to separate the conjugated diene that was found to be alpha-

phellandrene from eucalyptus oil by reacting it with maleic anhydride (the dienophile).

Observations: The main physical changes observed was a color change of the eucalyptus oil from clear to

a fluorescent yellow color upon adding 1.225 grams of maleic anhydride. The other color change

observed was after recrystallization of the diene. The solid crystals were originally yellow but then

turned all white in color after being crystallized which indicated that the majority of impurities must

have been removed.

My percent yield was 10.4% which is quite low. Possible sources of error may include solvolysis of my

product by methanol during the recrystallization phase which would have decreased my yield. Also my

product may have been hydrolyzed by water if any water happened to be added to my experiment by

mistake which would have also decreased my yield.

The melting point of my product was measured to be between 123C-126C which matches most closely

with that of the alpha-phellandrene diene. Also my IR results showed two bands at 1774.93 and 1835.84

cm(-1) as expected for the carbonyl stretches in maleic anhydride.

The possible structures for my Diels-Alder product are shown below in Figure 1:

Figure 1: Possible structures of product

I believe it my product was Structure A (the endo structure) because maleic anhydride yields the endo

product in which the bulkier substituents are closer to the c=c bond.