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 𝐶𝐻3
C=C C=C
𝐶𝐻3 𝐶𝐻3 𝐶𝐻3 H
Cis-2-butene Trans-2-butene
𝐻2 𝐻2
H H H 𝐶𝐻3
CH-CH CH-CH
𝐶𝐻3 𝐶𝐻3 𝐶𝐻3 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.

5. “ NEVER DO TOMORROW WHAT YOU
CAN DO TODAY”
THANK YOU……