Experiment 36: Determination of the Structure of a Natural Product in Anise Oil

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Name CHE 173 Sec # January 25, 2005 Experiment 36: Determination of the Structure of a Natural Product in Anise Oil

Purpose: The purpose of this experiment is to isolate the major component of anise oil and determine its identity and structure using melting point determination and IR spectroscopy.

Introduction: The major component of anise oil has the chemical formula C10H12O. This compound is said to be hydrogen deficient, meaning that it contains less hydrogen atoms than would be needed for each of the carbon atoms to have the maximum amount of hydrogen atoms attached. The IHD, or index of hydrogen deficiency for this molecule is 10. This indicates that there must be five rings or double bonds in the structure. Each of these would compensate for two of the missing hydrogen atoms. Since a saturated compound of the chemical formula C10H20O is formed upon catalytic hydrogenation of anise oil, it can be determined that the original structure contains four pi bonds, as eight hydrogen atoms were added. Through heating with hydriodic acid, anisene forms the phenol C9H9OH. This indicates that the major constituent of anise oil is an aryl methyl ether, with the chemical formula C9H9OCH3. With the formula rewritten, it can be seen that anisene has a disubstituted benzene ring with a methoxyl group (-CH3O). This means that the remaining constituent is –C3H5. In this experiment, anisene can then react with a methoxybenzoic acid to yield one of three products. The identity of the product, which can be decided by a melting point and IR spectrum analysis, can then infer the position of

the second substituent, and the overall structure of the major component of anise oil can be discovered (Lehman 292-294).

Materials and Methods: The materials and methods used during this experiment may be found in the laboratory manual (Lehman, p. 295-296). However some changes to the experiment procedure were made. Instead of five minutes, which was stated in the laboratory...
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