The word Conjugation comes from the Latin word that means “to link together”. In the terms of chemistry, conjugation is discussed when a situation occurs in which the pi system is linked to each other. Conjugation is basically:
- Delocalization of Electron
- By delocalization of electrons, it imparts stability.
- Conjugation is related to only with π bond and lone pair.
- It has no relation with the σ bond.
Now, we will discuss Hyperconjugation. Hyperconjugation is the process in which there is delocalization of electrons with the participation of sigma electrons. Hyperconjugation is the:
- Also called as σ – p orbital resonance and No bond Resonance.
- Resonance occurs in a single bounded compound.
- In this, new orbital having bonded characters are stabilized.
- It also involves the stabilization of molecules.
- By the following relation, it is clear that More conjugation is proportional to stability.
- More conjugation ∝ More Stability
Occurrence of Hyperconjugation:
Hyperconjugation takes place in the following molecules, compounds, and radicals.
- Occur in carbocations (primary, secondary, and tertiary)Occur in free radicle (Result due to homolytic fission in non – polar compound)
- Occur in Alkene (Unsaturated Hydrocarbons having double bond)
Hyperconjugation in Methyl group:
Hyperconjugation is the factor that describes the increasing stability of molecules by increasing the number of the alkyl group or carbo-cation on the radical in the compound. The basic condition for the hyperconjugation is that there should be an empty p – orbital in the compound in which the sigma electrons make the bond.
Let’s consider the hyperconjugation in the methyl group. First of all, we need to show the C-H σ-bond in the carbocation center. It is to be noted that empty p-orbital is associated with the positive charge in the same plane. Its geometry suggested that the σ- electrons are shifted to the empty p-orbital forming no bond.
This diagram is representing an empty p-orbital associated with the positive charge. Empty p-orbital is an essential condition for hyperconjugation.
This diagram is representing the shifting of σ- electron from alpha (α) Hydrogen into empty p-orbital. It is representing the stability of the compound according to Alpha (α) hydrogen.
Stability in Hyperconjugating Structures:
- The stability occurs in the compound because electrons first fill in the lower energy state. The stabilization occurs when orbital interactions lead the electron to fill in the lower energy state.
- So that the C-C bond rotates easily which allows the to rotate C-H bond. Therefore, it got stability due to rotation.
- As the schematic diagram representing the stability of the compound according to lower energy level.
Hence, there is a great conclusion that;
- Hyperconjugation occurs there is an empty p-orbital.
- It determines stability by the following relation:
- No. of α Hydrogen ∝ No. of no bond resonating structures ∝ Stability of No bond resonating structures.
- Hyperconjugation is not only limited to C-H σ-bonds but by C-C σ-bonds hyperconjugation is also carried out.