Q.4 - Organic Chemistry

Question

(a) Which double bonds in (E)-ocimene, a major component of the odor of lilac flowers, can exhibit stereoisomerism? (b) Draw a diastereomer of (E)-ocimene

Step-by-Step Solution

Answer

(a) The double bond where stereoisomer is possible is the major component of the odor of lilac flowers.

(b) The structure of (Z)-ocimene is drawn below:

Definition of stereoisomers

The isomers where the molecular formula and structures are the same but with different spatial arrangements of bonds are known as stereoisomers.

They are two different types – cis/Z and trans/E. Stereoisomers are considered particularly in those cases where the double-bonded alkene carry different groups.

Identification of the double bond

The double-bonded carbons are identified first.

Representation of the double bond in a compound

Finding of stereoisomers

(a) A stereoisomer is possible here since different alkyl groups are present in the same double-bonded carbon.

Representation of that alkene where stereoisomer is possible

The double bond where stereoisomer is possible is the major component of the odor of lilac flowers

Representation of that alkene which imparts fragrance

The color is due to different possible spatial arrangements present.

Drawing of (Z)-isomer

(b) Z-isomers are those where two high-priority groups are located in the same orientation. They are exactly the opposite of (E)-isomer, where they are located in an opposite orientation.

The structure of (Z)-ocimene is drawn below:

Representation of (Z)-ocimene