Hydrocarbons – NEET Important Questions, Reaction Mechanisms & Notes PDF

Hydrocarbons – Important NEET Questions, Concepts & Mechanisms

Hydrocarbons are the simplest organic compounds made up of only hydrogen and carbon. They form the basic framework of organic chemistry and are extremely important in the NEET Chemistry syllabus. In this post, we will cover the types of hydrocarbons, IUPAC naming, important reactions, mechanisms, and NEET questions with explanations.

What are Hydrocarbons?

Hydrocarbons are organic compounds consisting entirely of carbon and hydrogen atoms. They are categorized based on the type of bonds present between carbon atoms.

Types of Hydrocarbons

• Alkanes (Single bonds) - Saturated hydrocarbons (CnH_2n+2)
• Alkenes (One or more double bonds) - Unsaturated hydrocarbons (CnH_2n)
• Alkynes (One or more triple bonds) - Unsaturated hydrocarbons (CnH_2n-2)
• Aromatic hydrocarbons - Contain one or more benzene rings

Important IUPAC Rules

1. Select the longest carbon chain containing double/triple bonds.
2. Number the chain from the end nearest the double/triple bond.
3. Use suffixes like -ene for double bonds, -yne for triple bonds.
4. Use prefixes for substituents like methyl, ethyl, etc.

Important Reactions and Mechanisms

1. Combustion

All hydrocarbons burn in oxygen to form CO₂ and H₂O:

CH4 + 2O2 → CO2 + 2H2O

2. Substitution Reactions (Alkanes)

Example: Halogenation of methane

CH4 + Cl2 → CH3Cl + HCl

3. Addition Reactions (Alkenes/Alkynes)

Example: Ethene reacts with HBr

CH2=CH2 + HBr → CH3-CH2Br

4. Free Radical Halogenation (Mechanism)

• Initiation: Cl₂ → 2Cl·
• Propagation: CH₄ + Cl· → CH₃· + HCl
• Termination: CH₃· + Cl· → CH₃Cl

🧠 NEET Level MCQs with Answers and Explanation

Q1: What is the IUPAC name of CH₃-CH=CH₂?

• A. Propene ✅
• B. Butene
• C. Ethene
• D. Methene

Explanation: Three carbon atoms with one double bond = Propene.

Q2: Which hydrocarbon undergoes addition reactions?

• A. Methane
• B. Ethane
• C. Ethene ✅
• D. Benzene

Explanation: Alkenes like ethene undergo addition reactions.

📥 Download Hydrocarbon Notes PDF

📝 Conclusion

Hydrocarbons are the core of organic chemistry. Focus on their types, reactions, and mechanisms to score high in NEET Chemistry. Practice as many MCQs as possible from this chapter.