Question

Which of the following compounds will show geometrical isomerism?
(1) $2$ -butene
(2) Propene
(3) $1$ -phenylpropene
(4) $2$ -methyl-$2$-butene

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (D)

For exhibiting geometrical isomerism, presence of atleast one double bond and attachment of two different groups at the double bonded carbon atoms, are two essential conditions. The structures of the given compounds are as
1. $\underset{\text{2-butene}}{CH _{3} CH = CHCH _{3}}$
2. $\underset{\text{propene}}{CH _{3} CH = CH _{2}}$
3. $\underset{\text{1-phenyl propene}}{CH _{3} CH = \underset{\overset{|}{C_6}H_5}{CH _{2}}}$
4. $\underset{\text{2-methyl -2-butene}}{CH _{3} \overset{\underset{|}{C}H_3}{C} = CH - CH _{3}}$
Among the given, only $2$-butene and $1$-phenyl propene satisfy the conditions essential for geometrical isomerism, thus they exhibit geometrical isomerism.