Identification of a Conjugated Diene from Eucalyptus Oil

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  • Topic: Diene, Ice, Diethyl ether
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  • Published : June 20, 2012
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Rebecca Hardy Section 4
Ashleigh Stapleton
June 18, 2012
Experiment 32: Identification of a Conjugated Diene from Eucalyptus oil

Introduction
In this experiment, the purpose was to prepare the Diels-Alder adduct of the unknown conjugated diene in Eucalyptus oil and determine the approximate percentage of diene in Eucalyptus oil. To discover the product of this reaction, isolate the adduct, and classify the diene from the melting point of its adduct. The unknown was one of four conjugated dienes.

Maleic anhydride
Observation and Data
The three substances, anhydrous diethyl ether, maleic anhydride, and the eucalyptus oil combined a yellow mixture. The mixture produced a very strong scent. After heating the reaction under reflux for 45 min, crystals began to form when reaction was cooled to room temp. The crystals were white when formed and contained a little yellow tent to them. A lot of crystals were formed in the round bottom flask. The crystals were accidently dropped into the ice cold water forming a milky white substance, but this did not harm or contaminate the ending results. After vacuum filtration and being washed with the petroleum ether, the crystals turned pure white. Results and Discussion:

The anticipated result of this experiment was to identify one of four conjugated dienes. The melting point of the adduct unknown was found. The melting point range was 125℃- 127℃, supporting the results of an α-phellandrene. A theoretical error that could have transpired is using an abundant amount of maleic anhydride. To much maleic anhydride can be challenging to eliminate from the product. Side scraping of the flask and the vacuum filtration could explain technical errors in the result. Calculations:

2.5 g eucalyptus oil x .70 pure diene = 1.75 grams of maleic anhydride

Experimental:
2.5 g of eucalyptus oil was dissolved in 5 mL of anhydrous diethyl ether. 1.75 g of maleic anhydride was mixed in the mixture....
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