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

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