Question

Arrange the following alkenes in the decreasing order of stability:
 
Choose the correct answer from the options given below: 
 

• A. III $>$ II $>$ I $>$ IV
• B. I $>$ III $>$ II $>$ IV
• C. III $>$ I $>$ II $>$ IV
• D. I $>$ III $>$ IV $>$ II

Hint:

Alkene stability order: tetra $>$ tri $>$ trans-disubstituted $>$ cis-disubstituted.

Answer 1

The Correct Option is B

Step 1: Principle of alkene stability.
Stability of alkenes increases with:
Greater number of alkyl substituents on the double bond due to hyperconjugation, and
Lower steric strain in the molecule.
Step 2: Analysing structure I.
Alkene I is a tetra-substituted alkene.
It has maximum hyperconjugation and hence is the most stable.
Step 3: Analysing structure III.
Alkene III is a tri-substituted alkene.
It has fewer alkyl groups than I but more than II and IV, so it is next in stability.
Step 4: Analysing structure II.
Alkene II is a trans-disubstituted alkene.
Though it has fewer alkyl groups, trans configuration reduces steric repulsion, making it more stable than cis isomer.
Step 5: Analysing structure IV.
Alkene IV is a cis-disubstituted alkene.
It suffers from steric hindrance between substituents on the same side, making it the least stable.
Step 6: Final conclusion.
The decreasing order of stability is:
\[ \text{I}>\text{III}>\text{II}>\text{IV} \] which corresponds to Option (2).