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Organic Chemistry: Basics & Hydrocarbons

IUPAC nomenclature, isomerism, alkanes, alkenes, alkynes, and arenes

Key Concepts
  • IUPAC nomenclature: longest chain, lowest locants for the principal group
  • Isomerism: structural (chain, position, functional) and stereoisomerism
  • Electronic effects: inductive, resonance and hyperconjugation
  • Reaction mechanisms: SN1/SN2 substitution and E1/E2 elimination
  • Markovnikov and anti-Markovnikov addition to alkenes
Important Formulae
Degree of unsaturation DoU = (2C + 2 + N − H − X)/2
Carbocation stability 3° > 2° > 1° > methyl
Markovnikov's rule H adds to the carbon with more H atoms
Quick Tips
  • SN2: primary substrates, inversion of configuration, polar aprotic solvents.
  • SN1: tertiary substrates, racemisation, carbocation intermediate.
  • Aromaticity (Hückel): planar, conjugated and 4n+2 π electrons.
Sample Practice Questions

  1. The number of π electrons in a benzene ring is:

    • 3
    • 6
    • 9
    • 12
    Show answer

    Answer: 6

  2. According to Markovnikov's rule, hydrogen adds to the carbon atom that already has:

    • Fewer hydrogen atoms
    • More hydrogen atoms
    • A double bond
    • No hydrogen atoms
    Show answer

    Answer: More hydrogen atoms

  3. The hybridisation of the carbon atoms in ethyne (C₂H₂) is:

    • sp
    • sp²
    • sp³
    • sp³d
    Show answer

    Answer: sp

  4. The general molecular formula of alkanes is:

    • CₙH₂ₙ
    • CₙH₂ₙ₊₂
    • CₙH₂ₙ₋₂
    • CₙHₙ
    Show answer

    Answer: CₙH₂ₙ₊₂

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Practice Questions

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