Question

Which of the following does not show geometrical isomerism?

• A. 1,2-dichloro-1-pentene
• B. 1,3-dichloro-2-pentene
• C. 1,1-dichloro-1-pentene
• D. 1,4-dichloro-2-pentene

Answer 1

The correct option is C 1,1-dichloro-1-pentene

Conditions for geometrical isomers:
1) Free rotation must be restricted.
2) Both the terminals must be attached with different groups.
3) Terminals must not be in perpendicular planes.
a has two different groups attached to the terminal carbon of the double bond so it can show geometrical isomerism

b has two different groups attached to the terminal carbon of the double bond so it can show geometrical isomerism

c has two same groups (Cl) attached to the one of the terminal carbon of the double bond so it can't show geometrical isomerism

d has two different groups attached to the terminal carbon of the both double bond so it can show geometrical isomerism
hence correct option is c.