Hydrocarbons: The Energy Heroes ⛽
Hydrocarbons = Carbon + Hydrogen only! They’re everywhere in daily life:
- 🔥 Fuels: LPG (Liquified Petroleum Gas), CNG (Compressed Natural Gas), petrol, diesel, kerosene
- ♻️ Less pollution: LPG & CNG are cleaner options
- 🏭 Industrial uses: Make plastics (polythene, polypropene), paints, dyes, medicines
Why Study Hydrocarbons? 🎯
By the end of this unit, you’ll be able to:
- Name hydrocarbons using IUPAC rules
- Draw structures & isomers (same formula, different arrangement)
- Prepare hydrocarbons in the lab
- Tell apart alkanes, alkenes, alkynes & aromatics using properties
- Understand benzene’s special “aromaticity” ✨
Classification of Hydrocarbons 🧩
Based on carbon-carbon bonds:
| Type | Bonds Present | Examples |
|---|---|---|
| Saturated | Only C-C & C-H single bonds |
Alkanes (open chain) Cycloalkanes (closed chain) |
| Unsaturated | C-C double/triple bonds 😮 | Alkenes (C=C), Alkynes (C≡C) |
| Aromatic | Special ring structures ⭕ | Benzene |
Alkanes: The Simple Ones 😇
- Formula: \( \ce{C_nH_{2n+2}} \)
- Inert: Don’t react easily (old name: paraffins = low affinity)
- Start with Methane (\(\ce{CH4}\)) → replace H with \(-\ce{CH3}\) → get next alkane!
Methane’s Structure 🔺
- Tetrahedral shape (like a pyramid)
- Bond angle: 109.5°
- Bond lengths: C-H = 112 pm, C-C = 154 pm
- Bonds form by head-on overlap of carbon’s \(sp^3\) orbitals + hydrogen’s 1s orbital
Structure of Methane
H
|
H-C-H
|
H
Naming & Isomers 🤔
- First 3 alkanes (methane/ethane/propane) have only one structure.
- Butane (\(\ce{C4H10}\)) has 2 isomers:
- n-Butane: Straight chain ⛓️ (Boiling point: 273 K)
- Isobutane: Branched chain 🌿
n-Butane
H H H H
| | | |
H-C-C-C-C-H
| | | |
H H H H
NEET Must-Knows! 💡
- Classification: Saturated vs. unsaturated vs. aromatic hydrocarbons.
- Alkane general formula: \( \ce{C_nH_{2n+2}} \) and isomerism (e.g., butane’s 2 structures).
- Methane structure: Tetrahedral, bond angle 109.5°, bond lengths (C-H=112pm, C-C=154pm).
- Bonding in alkanes: Formed by head-on overlap of \(sp^3\) orbitals (carbon) + 1s orbitals (hydrogen).
