Chemistry Fundamental Principles of Organic Chemistry MDCAT 2013
PMDC Verified Question 81 of 83
The cis-isomerism is shown by:
A
\( \text{trans-2-butene} \) (Groups on opposite sides)
B
\( \text{cis-2-butene} \) (Groups on same side)
C
2-methyl-2-butene
D
1-butene
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: \( \text{cis-2-butene} \) (Groups on same side)
Concept:

Geometric (cis-trans) isomerism occurs in alkenes where there is restricted rotation around the double bond, and each carbon atom of the double bond is attached to two different groups.

Solution:

  • Cis-isomerism dictates that identical or similar groups (like two methyl groups or two hydrogen atoms) are on the same side of the double bond.


  • Option B represents a structure where the two bulky methyl groups are on the same side, creating a cis-geometry.


Why other options are incorrect:

Option A is the trans-isomer (groups on opposite sides). Options C and D do not exhibit cis-trans isomerism because one of the double-bonded carbons has two identical substituent groups.

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