Chemistry Fundamental Principles of Organic Chemistry MDCAT 2014
PMDC Verified Question 79 of 83
Which one of the following pair of compounds is cis and trans isomers of each other?

CH3 CH3 (I) CH3 CH3 (II)
A
Pair showing 2-butene with same and opposite sided methyls
B
Pair of chain isomers
C
Pair of structural isomers
D
Pair of identical molecules
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Pair showing 2-butene with same and opposite sided methyls
Concept:

A cis-trans isomer pair must have the exact same connectivity (same IUPAC name excluding the prefix) but differ in spatial arrangement around a rigid bond, such as a \( \text{C}=\text{C} \) double bond.

Solution:

  • The correct pair must show one molecule with identical groups on the same side of the double bond (cis) and the other with identical groups on opposite sides (trans).


  • Option A represents the geometric isomers of 2-butene.


Why other options are incorrect:

Other pairs represent molecules that differ in connectivity (structural isomers) or lack the necessary conditions for geometric isomerism entirely.

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