Hyperconjugation or Baker Nathan Effect

Avni Mishra

1. S.P.C Government College, Ajmer Topic Name: Hyperconjugation or Baker Nathan Effect Name: Avni Mishra Class: Msc . Chemistry ( Sem - 1)

2. Content Introduction to Hyperconjugation Conditions for Hyperconjugation Types of Hyperconjugation Effects of Hyperconjugation Reverse Hyperconjugation Reference

3. Introduction to Hyperconjugation Introduced by Baker and Nathan. Hyper means “EXCESSIVE” It involves sigma orbitals of (CH Bond) There is some ionic character between (CH Bond) There is Σ - Π or Σ -P orbital overlape It is a permanent effect

4. Conditions for Hyperconjugation Compound should have sp 2 hybride carbon of alkene carbocation or free radical. α – carbon should have atleast 1 hydrogen i.e α -hydrogen It is also called as no bond resonance but as carbon and hydrogen is present in the same solution there is some interactions present

5. Types of Hyperconjugation Sacrificial Hyperconjugation Isovalent Hyperconjugation There is charge separation between In this type of hyperconjugation there resonating forms, although charge is a charge seperation in actual dose not present on actual structure structure as well as resonating form.

6. Hyperconjugation in Propene In structure II, III, IV, there is a shifting of ∑-electron in C-H bond Hyperconjugation in Toluene

7. Effects of Hyperconjugation Stability of alkenes- More substitution falls for more stability so tetera substituted alkene is more stable Alkene < Monosubstituted < Bisubstituted < T risubstituted < T eterasubstituted

8. Effect on bond length Due to the H yperconjugation carbon-carbon bond of alkene aquarires some double bond character and carbon-carbon double bond acquire some single bond character So, the double bond length is increased and single bond length is decreased

9. Stability of free radicals Due to hyperconjugation tertiary free radical is more stable then primary free radical because there are 9 α -hydrogen

10. Reverse Hyperconjugation When there is electronegative atoms rather then hydrogen atoms then this effect operate in reverse direction. So, the conjugation in reverse system is reverse H yperconjugation α – h(x) α – Cl , F, Br, I

11. Reference CBH Pragati prakashan P.S. Kalsi