Hydrocarbons

1. Classification of Hydrocarbons:

• Acyclic Hydrocarbons:

  • Alkanes:
    • Saturated hydrocarbons with only C-C single bonds.
    • General formula: CnH2n+2.
    • Examples: Methane (CH4), Ethane (C2H6), Propane (C3H8)
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons
  • Alkenes:
    • Unsaturated hydrocarbons with at least one C=C double bond.
    • General formula: CnH2n.
    • Examples: Ethylene (C2H4), Propene (C3H6), Butene (C4H8)
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons
  • Alkynes:
    • Unsaturated hydrocarbons with at least one C≡C triple bond.
    • General formula: CnH2n-2.
    • Examples: Acetylene (C2H2), Propyne (C3H4), Butyne (C4H6)
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons

• Cyclic Hydrocarbons:

  • Cycloalkanes:
    • Saturated hydrocarbons with a ring of C-C single bonds.
    • General formula: CnH2n
    • Examples: Cyclopropane (C3H6), Cyclobutane (C4H8), Cyclopentane (C5H10)
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons
  • Cycloalkenes:
    • Unsaturated hydrocarbons with a ring of C-C single bonds and at least one C=C double bond.
    • Examples: Cyclohexene (C6H10), Cycloheptene (C7H12)
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons
  • Aromatic Hydrocarbons (Arenes):
    • Unsaturated hydrocarbons containing one or more benzene rings.
    • General formula: CnH2n-6 (for a single benzene ring)
    • Examples: Benzene (C6H6), Toluene (C7H8), Ethylbenzene (C8H10)
    • Reference: NCERT Chemistry Class 12, Chapter 13: Aromatic Hydrocarbons

2. Isomerism:

• Structural Isomerism:
  • Chain Isomerism: Isomers with different carbon chain arrangements.
  • Position Isomerism: Isomers with the same carbon chain but different positions of functional groups.
  • Functional Isomerism: Isomers with different functional groups.
• Stereoisomerism:
  • Geometrical Isomerism (E/Z): Isomers with different spatial arrangements of atoms or groups around a double bond.
  • Optical Isomerism (Enantiomers and Diastereomers): Isomers that are mirror images of each other but cannot be superimposed.
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons; NCERT Chemistry Class 12, Chapter 13: Aromatic Hydrocarbons

3. Reactions of Alkanes:

• Substitution Reactions:
  • Halogenation: Reaction of alkanes with halogens (Cl2, Br2, I2) to form alkyl halides.
  • Nitration: Reaction of alkanes with nitric acid (HNO3) and sulfuric acid (H2SO4) to form nitroalkanes.
• Combustion Reactions:
  • Reaction of alkanes with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O).
• Pyrolysis:
  • Thermal decomposition of alkanes at high temperatures to form smaller alkanes, alkenes, and alkynes.
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons

4. Reactions of Alkenes:

• Addition Reactions:
  • Hydrogenation: Reaction of alkenes with hydrogen (H2) in the presence of a catalyst (such as palladium or platinum) to form alkanes.
  • Halogenation: Reaction of alkenes with halogens (Cl2, Br2, I2) to form vicinal dihalides.
  • Hydration: Reaction of alkenes with water (H2O) in the presence of an acid catalyst (such as sulfuric acid) to form alcohols.
  • Hydrohalogenation: Reaction of alkenes with hydrogen halides (HCl, HBr, HI) to form alkyl halides.
  • Ozonolysis: Reaction of alkenes with ozone (O3) to form ozonides, which can be further cleaved to form aldehydes and ketones.
• Polymerization:
  • Reaction of alkenes with themselves to form polymers. For example, polymerization of ethylene (CH2=CH2) yields polyethylene (-(CH2-CH2)-n-).
    • Reference: NCERT Chemistry Class 11, Chapter 13: Hydrocarbons

5. Reactions of Alkynes:

• Addition Reactions:
  • Hydrogenation: Reaction of alkynes with hydrogen (H2) in the presence of a catalyst (such as palladium or platinum) to form alkenes and ultimately alkanes.
  • Halogenation: Reaction of alkynes with halogens (Cl2, Br2, I2) to form vicinal dihalides.
  • Hydration: Reaction of alkynes with water (H2O) in the presence of an acid catalyst (such as sulfuric acid) to form enols, which can tautomerize to form aldehydes or ketones.
  • Hydrohalogenation: Reaction of alkynes with hydrogen halides (HCl, HBr, HI) to form vinyl halides.
• Electrophilic Addition Reactions:
  • Addition of HCN: Reaction of alkynes with hydrogen cyanide (HCN) in the presence of a Lewis acid catalyst (such as BF3) to form immin