⌬ Organic Chemistry - Some Basic Principles

1. Tetravalence of Carbon

Carbon is tetravalent (valency of 4) due to its electronic configuration (excited state). It undergoes catenation (ability to form long chains and rings with other carbon atoms).

Carbon can form multiple bonds (C=C, C≡C) through sp², and sp hybridization, affecting the shape of molecules (tetrahedral, planar, linear).

2. IUPAC Nomenclature

A systematic method of naming organic compounds. The name consists of: Prefix + Word Root + Primary Suffix + Secondary Suffix.

Rules

1. Select the longest continuous carbon chain containing the principal functional group.

2. Number the chain giving the lowest locant to the principal functional group.

3. Priority order of functional groups: -COOH > -SO₃H > -COOR > -COCl > -CONH₂ > -CN > -CHO > >C=O > -OH > -NH₂.

3. Isomerism

Phenomenon where two or more compounds have the same molecular formula but different properties.

  • Structural Isomerism: Chain, Position, Functional, Metamerism.
  • Stereoisomerism: Geometrical (cis-trans) and Optical.

4. Fundamental Concepts in Reaction Mechanism

Cleavage of Covalent Bond

Homolytic Cleavage: Symmetrical breaking forming Free Radicals (highly reactive species with an unpaired electron).

Heterolytic Cleavage: Unsymmetrical breaking forming Carbocations (positive charge) and Carbanions (negative charge).

Nucleophiles: Electron-rich species (nucleus-loving). E.g., OH⁻, NH₃.
Electrophiles: Electron-deficient species (electron-loving). E.g., H⁺, NO₂⁺, BF₃.

5. Electronic Displacements in Covalent Bonds

Key Effects

1. Inductive Effect (I effect): Permanent displacement of sigma electrons along a carbon chain due to electronegativity difference. (-I and +I groups).

2. Electromeric Effect (E effect): Temporary complete transfer of pi electrons in the presence of an attacking reagent.

3. Resonance Effect (R or M effect): Delocalization of pi electrons. Stabilizes the molecule.

4. Hyperconjugation: Delocalization of sigma electrons of C-H bond into an adjacent empty p-orbital or pi-bond. (No-bond resonance).