Table of Contents
Hydrocarbons Chemistry Handwritten Notes PDF
Hydrocarbons are organic compounds composed of only carbon (C) and hydrogen (H).
They are the simplest form of organic compounds and classified mainly into:
- Alkanes (single bonds)
- Alkenes (one or more double bonds)
- Alkynes (one or more triple bonds)
- Aromatic hydrocarbons (benzene and its derivatives)
1. Alkanes (CnH2n+2)
Also called saturated hydrocarbons.
✴ Preparation:
- Hydrogenation of alkenes/alkynes
- Wurtz reaction:
2R–X + 2Na → R–R + 2NaX - Kolbe’s electrolytic method:
Electrolysis of sodium salt of fatty acid.
✴ Properties:
- Combustion:
Complete: CO₂ + H₂O
Incomplete: CO + C (soot) - Halogenation: Free radical substitution (initiation, propagation, termination)
2. Alkenes (CnH2n)
Unsaturated hydrocarbons with one or more double bonds.
✴ Preparation:
- Dehydration of alcohols
CH₃CH₂OH → CH₂=CH₂ + H₂O - Dehydrohalogenation of alkyl halides
- From vicinal dihalides
✴ Reactions:
- Addition reactions:
- With H₂ → alkane
- With halogens → dihalide
- With HBr (Markovnikov’s rule)
- Peroxide effect (Anti-Markovnikov) – only with HBr
- Oxidation:
- Baeyer’s test (alkene + cold KMnO₄ → glycol)
- Ozonolysis
3. Alkynes (CnH2n−2)
Contain one or more triple bonds.
✴ Preparation:
- Dehydrohalogenation of vicinal dihalides
- From calcium carbide:
CaC₂ + H₂O → HC≡CH + Ca(OH)₂
✴ Reactions:
- Addition of H₂, X₂, HX
- Oxymercuration (forms ketones)
- Polymerization
4. Aromatic Hydrocarbons (Arenes)
Example: Benzene (C₆H₆)
Structure: Hexagonal ring with delocalized π-electrons.
✴ Reactions:
- Electrophilic substitution:
- Nitration: HNO₃ + H₂SO₄
- Halogenation: Cl₂ in presence of FeCl₃
- Friedel–Crafts Alkylation & Acylation
- Side chain oxidation
- Combustion
Hydrocarbons Chemistry Handwritten Notes PDF
Important Concepts:
- Isomerism in hydrocarbons: Structural & geometrical
- Markovnikov’s Rule: H adds to C with more Hs
- Anti-Markovnikov’s Rule: (Peroxide effect)
- Baeyer’s Test: Purple KMnO₄ decolorizes = unsaturation