One of the flavouring compounds that have been isolated from aniseed oil is anethole.
a.What is the configuration of the molecule, cis or trans?
b. The compound will react with bromine.
i.What would you observe?
ii.Write an equation for the reaction.
a. To determine the configuration of the anethole molecule, cis or trans, we need to look at the arrangement of the substituents around the double bond. In the case of anethole, the two substituents attached to the double bond are a methoxy group (-OCH3) and a phenyl group (-C6H5).
If these two substituents are on the same side of the double bond, it is called cis configuration. If they are on opposite sides of the double bond, it is called trans configuration.
In the case of anethole, the methoxy group and the phenyl group are on opposite sides of the double bond, so the molecule has a trans configuration.
b. When anethole reacts with bromine, the following observations can be made:
i. A color change: Bromine is reddish-brown in color, and when it reacts with anethole, the red-brown color of bromine will disappear, indicating a reaction has taken place.
ii. To write the equation for the reaction between anethole and bromine, we need to understand the nature of the reaction. Bromine is an electrophile, meaning it seeks electrons to form a new bond. Anethole, being an alkene, has a π bond that can readily react with bromine.
The reaction between anethole and bromine can be represented by the following equation:
Anethole + Bromine → Bromoanethole
This equation shows that the bromine reacts with anethole to form a product called bromoanethole. The specific chemical structure of bromoanethole would depend on the exact position of bromine substitution on the anethole molecule.