Organic Chemistry lab
Due April 18, 2014
Title: Identification of Conjugated diene from Eucalyptus Oil Abstract:
The purpose of this experiment is to separate and identify a conjugated diene from eucalyptus oil by making its Diels-Alder adduct with maleic anhydride. The unknown is one of four conjugated dienes with its names and the melting points. The melting point of the adduct was 112°C revealed the identity of the diene in eucalyptus oil which was α-phellandrene. Introduction:
Some natural hydrocarbons are conjugated dienes or trienes. The majority of conjugated dienes have chemical properties not shared by other dienes. These adducts are typically crystalline solids that can be separated from the other compounds of an essential oil and used to identify the diene. Dienes and trienes occur in the essential oils of a number of plants and contribute to the flavors and aromas of such plants. The conjugated diene called β-myrcene is responsible for much of the fragrance and flavor of bay leaves. β-Myrcene is also present in hops, verbena, and lemongrass oil. β-Ocimene was first isolated from the Javanese oil of basil and is usually found in combination with allo-ocimene. Both of the phellandrenes derive their name from water fennel Phellandrium aquaticum, but α-phellandrene apparently doesn't occur in that plant; it was mistaken for its isomer, β-phellandrene, which does. α-Phellandrene is found in the oils of bitter fennel, ginger grass, cinnamon, and star anise; β-phellandrene also occurs in lemon oil and Japanese peppermint oil. Another cyclic diene, α-terpinene, is obtained from the essential oils of cardamom, marjoram, and coriander. The Diels-Alder reaction is stereoselective, usually yielding only one of several possible stereoisomers. Methods:
Dissolve 0.85 mL of the eucalyptus oil in 2 mL of anhydrous diethyl ether in a pear-shaped flask containing a magnetic spin vane, and add 450 mg of maleic anhydride. Gently reflux the...
References: Lehman, J. H. Operational Organic Chemistry, 2nd Ed. Allyn & Bacon:
Massachusetts, 1988, p. 221-229.
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