Hydrocarbons – NEET Chemistry Class 11

Hydrocarbons are organic compounds consisting exclusively of carbon and hydrogen atoms. They are classified based on the type of bonds between carbon atoms (single, double, triple, or aromatic). This chapter is fundamental for NEET, as it forms the backbone of organic chemistry and is frequently tested through conceptual, numerical, and reaction-based questions.

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Introduction to Hydrocarbons

Hydrocarbons are classified into:

• Alkanes – Saturated hydrocarbons with single C–C bonds.

• Alkenes – Unsaturated hydrocarbons with at least one C=C double bond.

• Alkynes – Unsaturated hydrocarbons with at least one C≡C triple bond.

• Aromatic Hydrocarbons – Compounds containing benzene rings.

Their physical and chemical properties depend on bond type, molecular structure, and functional groups.

Alkanes (CnH2n+2)

• Structure: Single bonds, tetrahedral geometry.

• Nomenclature: Prefix + “-ane” (e.g., Methane, Ethane).

• Reactions:

  • Combustion: CH₄ + 2O₂ → CO₂ + 2H₂O

  • Substitution: Free radical halogenation (e.g., CH₄ + Cl₂ → CH₃Cl + HCl)

Alkenes (CnH2n)

• Structure: Double bonds, planar geometry around C=C.

• Nomenclature: Prefix + “-ene” (e.g., Ethene, Propene).

• Reactions:

  • Electrophilic addition (e.g., HBr addition)

  • Hydrogenation: CH₂=CH₂ + H₂ → CH₃–CH₃

  • Hydration: CH₂=CH₂ + H₂O → CH₃–CH₂OH

Alkynes (CnH2n-2)

• Structure: Triple bonds, linear geometry around C≡C.

• Nomenclature: Prefix + “-yne” (e.g., Ethyne, Propyne).

• Reactions:

  • Electrophilic addition (similar to alkenes)

  • Oxidation: R–C≡C–R’ → Carboxylic acids

  • Acidic property: Terminal alkynes react with NaNH₂

Aromatic Hydrocarbons

• Structure: Benzene ring with delocalized π-electrons.

• Nomenclature: Parent compound = benzene, derivatives named based on substituents.

• Reactions:

  • Electrophilic substitution: Nitration, halogenation, sulfonation, Friedel-Crafts alkylation/acylation

  • Reduction of nitrobenzene to aniline

Importance for NEET Preparation

• Hydrocarbons are high-yield topics for NEET.

• Questions include nomenclature, reactions, physical properties, and mechanisms.

• Understanding hydrocarbons lays the foundation for reaction mechanisms, functional group chemistry, and organic synthesis.

Previous Year NEET Questions – Insights

• Naming alkanes, alkenes, alkynes, and aromatic compounds.

• Predicting products of hydrocarbon reactions.

• Understanding combustion, substitution, addition, and electrophilic substitution reactions.

• Recognizing physical properties (boiling/melting points, solubility) based on molecular structure.

Study Tips for Students

1. Memorize Hydrocarbon Nomenclature – Know common and IUPAC names.

2. Practice Reaction Mechanisms – Focus on substitution, addition, and electrophilic substitution.

3. Draw Structures – Visualize molecules and their reactions.

4. Solve Previous Year NEET Questions – Reinforces conceptual clarity and speed.

5. Use NCERT Examples – Most NEET questions are directly from NCERT.

Conclusion

Mastering Hydrocarbons is essential for NEET success. It provides a strong foundation for understanding organic reactions, functional groups, and reaction mechanisms. Clear knowledge of alkanes, alkenes, alkynes, and aromatic compounds ensures students can confidently tackle both conceptual and numerical NEET questions.