Hydrocarbons – The Simplest Carbon Compounds

📚 Key Concepts

🔹 Real-Life Example

When you light a gas stove, you’re burning methane (CH₄). The petrol in your car contains octane (C₈H₁₈). The LPG cylinder in your kitchen has butane (C₄H₁₀). All these are hydrocarbons – compounds containing only carbon and hydrogen atoms.

Hydrocarbons: Organic compounds composed of only carbon and hydrogen atoms. They are the simplest organic compounds and serve as parent compounds for more complex organic molecules.

🧪 Classification of Hydrocarbons

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🔸 Saturated Hydrocarbons (Alkanes)

General Formula: CₙH₂ₙ₊₂

Characteristics:

  • Contain only single C-C bonds
  • Also called paraffins (little affinity for reactions)
  • Relatively unreactive

Examples:

  • Methane (CH₄): Natural gas, biogas
  • Ethane (C₂H₆): Component of petroleum gas
  • Propane (C₃H₈): LPG for cooking
  • Butane (C₄H₁₀): Lighter fuel, LPG

🔸 Unsaturated Hydrocarbons

Alkenes (Double bonds):

  • General Formula: CₙH₂ₙ
  • Examples: Ethene (C₂H₄), Propene (C₃H₆)
  • More reactive than alkanes

Alkynes (Triple bonds):

  • General Formula: CₙH₂ₙ₋₂
  • Examples: Ethyne (C₂H₂) – acetylene for welding
  • Most reactive hydrocarbons

🧪 Nomenclature of Hydrocarbons

🔸 IUPAC Naming Rules

  1. Identify the longest carbon chain
  2. Number the chain from the end giving lowest numbers to branches
  3. Name the substituents (branches)
  4. Arrange in alphabetical order

Common Examples:

  • 1 Carbon: Meth-
  • 2 Carbon: Eth-
  • 3 Carbon: Prop-
  • 4 Carbon: But-
  • 5 Carbon: Pent-

Suffixes:

  • Single bonds: -ane
  • Double bonds: -ene
  • Triple bonds: -yne

🔍 Advanced: Structural Isomerism

Compounds with same molecular formula but different structural arrangements. For example, butane (C₄H₁₀) can exist as:

  • n-butane (straight chain)
  • iso-butane (branched chain)