Chemical Hybridization and Electronic Effects Explained

Hybridization in Hydrocarbons

Ethane (C₂H₆)

Ethane is sp³ hybridized with a tetrahedral geometry and a bond angle of 109.5°. One sp³ orbital of each carbon atom undergoes internuclear axial overlapping to form a sigma (σ) bond. Three sp³ orbitals of each carbon atom undergo internuclear axial overlapping with the 1s orbital of hydrogen atoms to form three sigma bonds each.

Ethene (C₂H₄)

In C₂H₄, each carbon atom is sp² hybridized and lies in a trigonal planar geometry with a bond angle of 120°. Out of three sp² hybrid orbitals:

• One sp² orbital of one carbon atom undergoes internuclear axial overlapping with the sp² orbital of another carbon atom to form one sigma (σ) bond.
• Two sp² orbitals of each carbon atom undergo internuclear axial overlapping with the 1s orbital of hydrogen atoms to form two sigma bonds each.
• The remaining unhybridized p-orbital of each carbon atom undergoes lateral overlapping to form one pi (π) bond.

Ethyne (C₂H₂)

In C₂H₂, each carbon atom is sp hybridized and lies in a linear geometry with a bond angle of 180°. Out of two sp hybrid orbitals:

• One sp orbital of one carbon atom undergoes internuclear axial overlapping with the sp orbital of another carbon atom to form one sigma (σ) bond.
• One sp orbital of each carbon atom undergoes internuclear axial overlapping with the 1s orbital of a hydrogen atom to form one sigma bond each.
• The two unhybridized p-orbitals of each carbon atom undergo lateral overlapping to form two pi (π) bonds.

1. Inductive Effect (I-Effect)

The inductive effect is the permanent shifting of sigma (σ) electrons along a carbon chain due to electronegativity differences.

• Occurs through sigma bonds only
• Decreases with distance
• It is a permanent effect

2. Resonance Effect (Mesomeric Effect)

Resonance effect is the delocalization of π electrons in molecules having double bonds or lone pairs.

• Occurs through pi bonds
• Permanent effect
• Makes the molecule more stable

3. Hyperconjugation

Hyperconjugation is the delocalization of sigma electrons of a C-H bond into an adjacent empty p-orbital. It is also known as:

• No-bond resonance
• Baker-Nathan effect

4. Electromeric Effect (E-Effect)

Temporary shifting of π electrons under the influence of an attacking reagent.

• Temporary effect
• Only occurs in the presence of an attacking reagent
• Disappears after the reaction

Periodic Table Data