Stability of alkenes

Stability of Alkenes for Pharma Students and Faculty

1. Stability of alkEnes For B-Pharm students Presented by- sandhya punetha

2. Stability of alkenes Tetra substituted alkenes are more stable than di; tri; mono substituted alkenes. In di-substituted alkenes, trans form is more stable than cis form of di-substituted alkenes. Because more substitution leads to more conjugation , more conjugation directly proportional to stablility . Hyperconjugation means number of alpha hydrogen to alpha carbon atoms. Less stable isomer has higher energy which is identified by heat of hydrogenation.

3. Eg- Cis-2-butene exerts- 28.6 kcal/mole energy while trans-2-butene exerts – 27.6 kcal/mole energy on hydrogenation of 2-butene. H H H C=C C=C H Cis-2-butene Trans-2-butene H H H CH-CH CH-CH H  

4. If an alkene as higher heat of hydrogenation it means it has more energy and is less stable. In the above case cis isomer has more energy than trans isomers therefore, cis isomer is less stable.

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