Question

Which of the following compounds will exhibit geometrical ismerism?

• A. 1-phenyl-2-butene
• B. 3-phenyl-1-butene
• C. 2-phenyl-1-butene
• D. 1,1-diphenyl-1-propene

Answer 1

The correct option is A 1-phenyl-2-butene

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.

Draw the structure, and observe whether the two doubly bonded carbon atoms are differently substituted or not.

Note that only in first structure both of the doubly bonded carbon atoms have different groups. Hence, the correct answer is option (a).