Chapter 8, Problem 24P

Rank the alkenes shown in the ball-and-stick models (A-C) in order of increasing stability.

Interpretation Introduction

Interpretation: The given alkenes shown in the ball-and-sticks models are to be ranked in order of increasing stability.

Concept introduction: Stability of alkenes is governed by Zaitsev rule. More substituted alkenes are more stable.

Answer to Problem 24P

The stability order of given alkenes is $\text{B}<\text{C}<\text{A}$.

Explanation of Solution

According to Zaitsev rule the more substituted or more alkylated alkene is more stable which makes the order of stability as tetra-substituted > tri-substituted > di-substituted > mono-substituted.Trans alkenes are more stable than cis alkenes as there substitutions are attached far from each other which makes them less sterically hindered. In the given question A is trans-disubstitued alkene, B is mono-substituted alkene while C is cis-disubstitued alkene.

Explain how you got molecular structure from the given ball and stick model.

Figure 1

So, A and C are more stable than B.A is more stable than C as A is trans isomer while C is cis isomer. Therefore, stability order of given alkenes is $\text{B}<\text{C}<\text{A}$.

Figure 2

Conclusion

The stability order of given alkenes is–$\text{B}<\text{C}<\text{A}$.