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General Organic Chemistry (GOC) – Jee mains Revision series

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General Organic Chemistry (GOC) – Conceptual Foundation

General Organic Chemistry explains why molecules behave the way they do. Every reaction mechanism, acidity order, and stability trend originates here. Mastering GOC means predicting reactions instead of memorizing them.

1. Reactive Intermediates

(a) Carbocation (C⁺)

  • Carbon atom with positive charge and 6 electrons
  • Hybridization: sp², planar structure
  • Acts as an electrophile
Stability Order:
3° > 2° > 1° > CH₃⁺

Reason: +I effect and hyperconjugation stabilize positive charge.

(b) Carbanion (C⁻)

  • Carbon atom with negative charge and lone pair
  • Hybridization: usually sp³
  • Acts as a nucleophile
Stability Order:
CH₃⁻ > 1° > 2° > 3°

Reason: Electron donating alkyl groups destabilize negative charge.

(c) Free Radical (•)

  • Carbon with one unpaired electron
  • Neutral species
  • Hybridization: sp²
Stability Order:
3° > 2° > 1° > CH₃•

Reason: Hyperconjugation and alkyl group stabilization.

2. Inductive Effect (I-Effect)

Inductive effect is the permanent polarization of σ-bonds due to electronegativity difference. It decreases rapidly with distance.

(a) +I Effect (Electron Donating)

Group Strength
–C(CH₃)₃Strong +I
–CH₃Weak +I

+I effect stabilizes carbocations and destabilizes carbanions.

(b) –I Effect (Electron Withdrawing)

Group Strength
–NO₂Strong –I
–Cl, –FModerate –I

–I effect increases acidity and stabilizes carbanions.

3. Resonance Effect (R-Effect)

Resonance occurs when a molecule cannot be represented by a single structure. Actual structure is a resonance hybrid.

Hückel’s Rule (Aromaticity)

A planar, cyclic, fully conjugated molecule is aromatic if:

Number of π electrons = (4n + 2)

Examples: Benzene (6), Cyclopentadienyl anion (6)

Bredt’s Rule

A double bond cannot exist at a bridgehead carbon of a small bicyclic system because required planarity is impossible.

Positive and Negative Resonance

Effect Groups Impact
+R –OH, –NH₂ Activates benzene ring
–R –NO₂, –COOH Deactivates benzene ring

4. Hyperconjugation

Hyperconjugation is the delocalization of σ-electrons of C–H bond with adjacent empty or partially filled p-orbital.

  • Also called “no-bond resonance”
  • Stabilizes carbocations and alkenes
More α-hydrogens → more hyperconjugation → more stability

5. Acidic and Basic Strength

Acidity

Stronger acid → more stable conjugate base.

Factors increasing acidity:
  • –I effect
  • Resonance stabilization
  • Higher electronegativity
  • Greater s-character (sp > sp² > sp³)

Basicity

Stronger base → more available lone pair.

Factors affecting basicity:
  • +I effect increases basicity
  • Resonance decreases basicity
  • Solvent and steric hindrance matter

✔ Concept-driven, not memory-driven
✔ Reaction prediction becomes intuitive
✔ Forms backbone of entire Organic Chemistry

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