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Organic Chemistry: Reactions & Biomolecules

Functional groups, named reactions, polymers, carbohydrates, amino acids, and nucleic acids

Key Concepts
  • Functional groups determine reactivity and product type
  • Named reactions: Aldol, Cannizzaro, Friedel–Crafts and Grignard
  • Oxidation and reduction interconvert functional groups
  • Polymers: addition and condensation polymerisation
  • Biomolecules: carbohydrates, proteins, and nucleic acids
Important Formulae
Aldol condensation Carbonyl with α-H + base → β-hydroxy carbonyl
Cannizzaro reaction Aldehyde with no α-H + strong base → alcohol + acid
Grignard reaction RMgX + carbonyl → alcohol (after hydrolysis)
Peptide bond −COOH + H₂N− → −CO−NH− + H₂O
Quick Tips
  • Aldehydes are more reactive than ketones towards nucleophiles.
  • In DNA, A pairs with T (2 H-bonds) and G pairs with C (3 H-bonds).
  • Friedel–Crafts fails on strongly deactivated (e.g. nitro-substituted) rings.
Sample Practice Questions

  1. The functional group present in a carboxylic acid is:

    • −OH
    • −CHO
    • −COOH
    • −NH₂
    Show answer

    Answer: −COOH

  2. In a DNA molecule, adenine pairs with:

    • Guanine
    • Cytosine
    • Thymine
    • Uracil
    Show answer

    Answer: Thymine

  3. A Grignard reagent (RMgX) reacts with a carbonyl compound to give, after hydrolysis, an:

    • Alkane
    • Alcohol
    • Acid
    • Ester
    Show answer

    Answer: Alcohol

  4. The aldol condensation requires a carbonyl compound that has an:

    • α-hydrogen
    • aromatic ring
    • halogen atom
    • oxygen atom only
    Show answer

    Answer: α-hydrogen

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Practice Questions

Practise randomly selected JEE questions on Organic Chemistry: Reactions & Biomolecules. Answers are revealed after each question.

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