Question

The total number of geometrical isomers possible in following compound is

• A. 2
• B. 1
• C. 6
• D. 8

Answer 1

The correct option is D 8

The given compound is a unsymmetrical compound. It has different terminal groups (methyl and phenyl).
The formula used to determine the number of geometrical isomers in compound having different terminal groups is, $2^n$, where n is the number of doube bond present in the molecule.
In the given compound we have 2 double bond and one ring with double bond. Double bond in ring doesnot show geometrical isomer so ring with double is equivalent to one double bond. Thus, n = 3
Therefore,
No. of geometrical isomers = $2^n$
= $2^3$
= 8.

Hence, unsymmetrical compound with 2 double bonds and one doubly bonded ring has 8 stereoisomers.