Monday, February 16, 2009

Identification of a Conjugated Diene from Eucalyptus Oil

Purpose of Experiment
The purpose of this experiment was identify an unknown conjugated diene from Eucalyptus Oil. Diel-Alder adduct of the unknown conjugated is prepared in Eucalyptus oil , separated and identified using the melting point of the adduct. The reaction carried out in this experiment is as follows :

Methods and proceduce
Into a 5-ml conical vial, 1.00g of eucalptus oil was dissolved in 2.0ml of anhydrous ethyl ether. Then 0.360g of powdered maleic anhydride was added. The reaction was then heated using a cooled condenser for under a gentle reflux at about sixty degrees forty-five minutes.
After the reaction was over, the mixture was let to cool to room temperature. Crystals formed in the vial as the mixture cooled. When crystallization was almost complete, the vial was then cooled in an ice bath for a few minutes to allow more formation of cryatals.
The adduct was collected by vaccum filteration with 1.5ml of cold, low-boiling point ether used to wash the cystals off the vial. The adduct was then recystallized from dry methanol just immediately the methanol began to boil. The adduct was dried and measured. The melting point of the adduct was also recorded and used to deduce the identity of the eucalyptus oil diene.
The weight of the product from the experiment was 0.47g, and the melting point obtained fell in the range of 107°C-112°C. Therefore, the conjugated diene was α-phellandrene, which has a melting point between 126°C-127°C, because it has a melting point which is closer to that of the unknown.
Below is the percent yield of the product obtained :
(1g oil 50% eucalyptus oil )/(136.2g/mol) = 0.00367mole of eucalyptus oil
Because euclyptus oil and the unknown compound are in 1:1 mole ratio, 0.00367mole of unknown compound (α-phellandrene) will be obtained.
Actual of α-phellandrene = 0.47grams
Theoretical of α-phellandrene = 0.00367moles x molecular weight of α-phellandrene = Mgrams
Percentage yield = (0.47g )/Mg x 100%=Y%
The yield obtained from the experiment was 94.0% of the actual yield. Possible sources led to the error in the results. Some of the product might have been lost in the process of vacuum filteration. This lead to few crystals been obtained as product, and decreased the weight. The reaction took longer time to react because the stirring bar did not properly stirr the solution. It might have also lead to less yield of product.
The melting point obtained from the solution was between 107°C-112°C , and differed from the actual melting point by 15°C-19°C. The discrepancy in the result might have been from the equipment used. The solution was inserted into the melting point apparatus while it was warm (about 60°C). This might have led to the lower boiling point obtained as supposed to that of α-phellandrene, which is between 126°C-127°C.
The method of characterization used in this experiment supports purity of the product obtained. The product was much like the hypothesized diene. The physical features such as color, which was white, melting point, melting point, texture and so on are similar to that of α-phellandrene.
The purpose of the experiment was to identify an unknown diene using the Diels-Alder reaction. The objective and purpose of the experiment was obatined with the method that was implemented to purify the product. One way this experiment could be improved is to strictly follow the procedures of the experiment, and avoid taking the melting point with a melting point apparatus that is not at room temperature.

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