Question

The total number of stereoisomers of a compound, given below, is

(A) 2
(B) 4
(C) 6
(D) 8

Answer 1

Hint: Stereoisomerism is the type of isomerism in which the two molecules have the same molecular formula and the same sequence of bonded atoms but differ in the three-dimensional orientations of atoms in space. It is also known as spatial isomerism. Due to the presence of chiral centres, the stereoisomers are optically active.

Formula Used: The total number of stereoisomers is given by ${{2}^{n}}$; where n is the sum of the number of double bonds and chiral carbons.

Complete Step by Step Answer:
The given compound is 4-methyl Octa-2,5-diene. Its structure is given by

The given compound is unsymmetrical. It contains two double carbon-carbon double bonds and one chiral carbon.
So, n= no. of double bonds + no. of chiral carbons
$n=2+1$
$n=3$
The total number of stereoisomers = ${{2}^{n}}$
$={{2}^{3}}$
$=8$

The total number of stereoisomers in the given compound is 8.
Correct Option: (D) 8.

Additional Information: The stereoisomer is of two types: diastereomers and enantiomers. The two isomers are said to be diastereomers if the two isomers are not mirror images of each other. The diastereomers vary in their physical and chemical properties. The diastereomers are referred to as epimers if they differ only at one stereocenter. The two isomers are said to be enantiomers if the two isomers are not mirror images of each other. The enantiomers have identical properties.

Note: The value of n should be correctly noted to find the actual number of stereoisomers of a compound.