Question

First, you name both the compounds. Yes, both of them have the same name. Yet, are they really the same structure, or they are somehow different? Careful inspection should convince you that they are indeed different. Now, how their physical and chemical properties differ? Generally,
i) Cis-isomer has more dipole moment than trans-isomer.
ii) Cis is less stable than trans.
iii) The boiling points of cis isomers are more than those of trans isomers (remember boiling points are directly related to polarity which is determined by dipole moment).
iv) Chemical reactivities of cis and trans also differ from each other.

Which of the following compounds exhibit geometrical isomerism?

(A) $C{H}_2-CH=C{H}_3$
(B) $C{H}_3-CH=CH-C{H}_3$
(C) $C{H}_3-CH=C=CH-C{H}_3$
(D) $C{H}_3-CH=C=C=CH-C{H}_3$

• A. B, D
• B. B, C, D
• C. B, C
• D. A, C

Answer 1

The correct option is A B, D

The compounds (B) and (D) exhibit geometrical isomerism.
As they contain different groups attached to each C atom joined by double bond.
In compound A, geometrical isomerism is not possible as two same H atoms are attached to C atom joined by double bond.
In compound C, geometrical isomerism is not possible as the molecule is non planar.