Question

How many stereoisomers do the molecules have?
$C{H_3}CH = CHC{H_2}CHBrC{H_3}$
A.$2$
B.$4$
C.$6$
D.$8$

Answer 1

In chemistry, each compound or polyatomic ion has its different property and formula. But, polyatomic ions have the same formula but a different structure that is known as isomerism. Stereoisomer is the form of isomerism.

Complete step by step answer:
Firstly, let's have a look at stereoisomers.
Stereoisomer- It is a special form of isomer in which the same constitution of the atom or same molecular formula but different its orientation or structure. It has two types that are Enantiomers, Diastereomers.
Enantiomers- When two stereoisomers mirror each other or its reflection related to each other is known as enantiomers.
Diastereomers- When two stereoisomers are not related to each other through reflection or they do not look like mirror images of each other is known as diastereomers. E-Z isomer, meso compounds, cis-trans isomers.
To find the number of stereoisomers we need to find the number of optical isomers and geometrical isomers.
we have given $C{H_3}CH = CHC{H_2}CHBrC{H_3}$ its structure is
$C{H_3} - \mathop {\mathop C\limits_| }\limits_H = \mathop {\mathop C\limits_| }\limits_H - C{H_2} - \mathop {\mathop {\mathop {\mathop C\limits^| }\limits^H }\limits_| }\limits_{Br} - C{H_3}$
Number of optical isomers = ${2^n}$ $n$ = number of asymmetric carbon atom
$n$ =$1$
number of optical isomers = ${2^1} = 2$
Number of geometrical isomer= ${2^n}$ $n$ = number of double bonds
$n = 1$
number of geometrical isomer= ${2^1} = 2$
hence, the total number of stereoisomers = optical number $+$ geometrical number
= $2 + 2$
= $4$
Now, we got the number stereoisomers that are $4$. Therefore, the option $B$ is the correct answer.

Note:
Cis-trans isomer- In this, the functional group attaches on the same side of the carbon chain is known as cis while the functional group attached on the opposite side is known as the trans isomer. E-Z isomer describes double bond and its substituents. Asymmetric carbon- It is a type of carbon that is connected to four different types of atoms.