Chapter 7: Fundamental Principles of Organic Chemistry

Vital Force Theory: Early belief that organic compounds could only be produced by living organisms. Rejected by Wohler (1828) who synthesized Urea from Ammonium Cyanate.

Modern Definition: Chemistry of Hydrocarbons and their derivatives.

• Catenation: Self-linking property of Carbon to form long chains and rings.
• Non-ionic Character: Covalent bonds involved.
• Similarity in Behavior: Homologous Series.
• Solubility: Generally insoluble in water, soluble in organic solvents.
• Isomerism: Same molecular formula, different structural formula.

• Coal: Formed by carbonization of trees. Types: Peat, Lignite, Bituminous, Anthracite. Destructive distillation gives Coal Gas, Coal Tar, Coke.
• Natural Gas: Mixture of low boiling hydrocarbons. Mainly Methane (85%).
• Petroleum: Breakdown of organic matter. Fractional distillation yields Asphalt, Lubricating Oil, Diesel, Kerosene, Gasoline (Petrol), etc.

Cracking

Breaking of higher hydrocarbons into lower ones.

• Thermal Cracking: High Temp/Pressure. Produces unsaturated alkanes.
• Catalytic Cracking: Lower Temp (500°C), Pressure (2 atm), Catalyst (SiO2+Al2O3). Better gasoline.
• Steam Cracking: High Temp (900°C) with steam. Produces lower unsaturated hydrocarbons.

Reforming

Conversion of straight chain hydrocarbons into branched chain to improve Octane Number (reduce knocking).

• Open Chain (Acyclic): Straight or Branched.
• Closed Chain (Cyclic):
  • Homocyclic: Ring of only Carbon atoms. (Alicyclic vs Aromatic).
  • Heterocyclic: Ring contains other atoms (N, O, S) e.g., Pyridine, Furan.

• sp³: 1s + 3p. Tetrahedral (109.5°). e.g., Methane (CH4), Ethane. Alkanes.
• sp²: 1s + 2p. Trigonal Planar (120°). e.g., Ethene. Alkenes.
• sp: 1s + 1p. Linear (180°). e.g., Ethyne. Alkynes.

Structural Isomerism

• Chain: Different carbon skeleton (n-Butane vs Isobutane).
• Position: Different position of functional group (1-Chloropropane vs 2-Chloropropane).
• Functional Group: Different functional group (Alcohol vs Ether).
• Metamerism: Unequal distribution of Carbon atoms around functional group (Ethers, Ketones).
• Tautomerism: Shifting of proton (Amino acids Zwitter ion).

Geometric (Cis-Trans) Isomerism

Due to restricted rotation about double bond. Groups on same side (Cis), opposite side (Trans).