Hydrocarbons

Alkanes


Saturated hydrocarbons
General formula CnH2n + 2
Also called paraffins (little affinity)

Types of preparation

  • Kolbe's electrolysis
  • Decarboxylation
  • Coupling reaction
  • Carbides electrolytes
  • Reduction
  • Others

Kolbe's electrolysis :
Electrolyte : RCOONa, RCOOK

At anode :

\dot{R} + \dot{R} \rightarrow R - R

At cathode :
2H_{2}O + 2e^{-} \rightarrow H_{2} + 2OH^{-}
2Na^{+} + 2OH^{-} \rightarrow 2NaOH
CH_{3}COONa (aq) \xrightarrow[]{Electrolysis} CH_{3}COO^{-} + Na^\oplus
At anode :

At cathode :
2H_{2}O + 2e^{-} \rightarrow H_{2} + 2OH^{-}
2Na^{+} + 2OH^{-} \rightarrow 2NaOH

Coupling reactions :

  • Wurtz reaction
  • Frankland reaction

Wurtz reaction :

Intramolecular wurtz reaction :

Wurtz–Fitting reaction :

Fitting reaction :

Frankland reaction :
R - X + Zn + X - R\rightarrow R - R + ZnCl_{2}
CH_{3}Cl + Zn + ClCH_{3}\rightarrow R - R + ZnCl_{2}

Part1: View the Topic in this Video from 0:35 to 52:40

Part2: View the Topic in this Video from 0:33 to 52:45

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1. General formula of Alkanes = [CnH2n + 2]

2. Combustion C_{n}H_{2n + 2} + \frac{\left(3n + 1\right)}{2}O_{2} \rightarrow nCO_{2} + \left(n + 1\right)H_{2}O

3. Boiling point ∝ surface area (or) Boiling point ∝ \tt \frac{1}{Branching}