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Question
Which of the following exhibits geometrical isomerism?
Which of the following exhibits geometrical isomerism?
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Solution
The correct option is A
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.
b and d are even cumulenes so they will not show geometrical isomerism. In even cumulenes, groups on the terminal carbons exist in a perpendicular plane. now for compounds to exhibit geometrical isomerism, groups on the terminal carbons must be in the same plane.
(a) is odd numbered cumulene. Odd numbered cumulenes show geometrical isomerism. When there is three consecutive double bonds, terminals lie in the same plane giving geometrical isomerism. Hence (a) will show geometrical isomerism.
(c) is also odd numbered cumulene but both the terminals attached with terminal carbon is same group thus it will not show geometrical isomer.
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.
b and d are even cumulenes so they will not show geometrical isomerism. In even cumulenes, groups on the terminal carbons exist in a perpendicular plane. now for compounds to exhibit geometrical isomerism, groups on the terminal carbons must be in the same plane.
(a) is odd numbered cumulene. Odd numbered cumulenes show geometrical isomerism. When there is three consecutive double bonds, terminals lie in the same plane giving geometrical isomerism. Hence (a) will show geometrical isomerism.
(c) is also odd numbered cumulene but both the terminals attached with terminal carbon is same group thus it will not show geometrical isomer.
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