The chemicals and the reaction conditions required for the preparation of ethane are

Answer: Ethane can be prepared most cleanly by several standard methods; the most exam-relevant chemicals and reaction conditions are 

(i) Wurtz reaction: methyl halide + sodium metal in dry ether, 

(ii) Kolbe electrolysis: aqueous sodium acetate under electrolysis, 

(iii) soda-lime decarboxylation: sodium propionate heated with soda-lime, and 

(iv) catalytic hydrogenation: ethene or acetylene + H₂ over Ni/Pd/Pt at elevated temperature.

Preparation of Ethane: chemicals and reaction conditions

1) Wurtz reaction (best known laboratory route)

• Chemicals: Methyl halide (CH₃Cl or CH₃Br), sodium metal, anhydrous diethyl ether.
• Conditions: Absolutely dry ether as solvent. Inert atmosphere preferred. Stir at low temperature first, then allow to warm to room temperature; maintain anhydrous setup to avoid sodium side reactions.
• Reaction: 2 CH₃X + 2 Na → C₂H₆ + 2 NaX (X = Cl, Br).
• Notes: This is a coupling of two methyl radicals formed via single-electron transfer from sodium. Works best with primary halides. Side-coupling is minimal because only methyl is present, so the only product alkane is ethane.

2) Kolbe electrolysis (anodic coupling of acetate)

• Chemicals: Sodium acetate or potassium acetate dissolved in water or aqueous ethanol.
• Conditions: Electrolysis in a divided or undivided cell. Inert electrodes such as platinum or graphite. Current density controlled to avoid over-oxidation. Ambient to warm temperature.
• Anode process: 2 CH₃COO⁻ → CH₃· + CO₂ + e⁻ (twice); radical coupling gives C₂H₆.
• Overall reaction: 2 CH₃COONa + 2 H₂O → C₂H₆ + 2 CO₂ + H₂ + 2 NaOH.
• Notes: Gas mixture from the cell contains ethane, carbon dioxide, and hydrogen. Drying and CO₂ scrubbing give purified ethane. This method emphasizes preparation of ethane by Kolbe electrolysis in many syllabi.

3) Soda-lime decarboxylation (one-carbon removal)

• Chemicals: Sodium propionate (C₂H₅COONa), soda-lime (NaOH + CaO).
• Conditions: Heat the dry salt with soda-lime around 350–400 °C in a hard-glass tube; collect evolved gas over water.
• Reaction: C₂H₅COONa + NaOH → C₂H₆ + Na₂CO₃.
• Notes: Decarboxylation gives an alkane with one less carbon than the acid. Using propionate therefore yields ethane. This is a staple “preparation of ethane by decarboxylation” procedure.

4) Catalytic hydrogenation (Sabatier method)

• Chemicals: Ethene (C₂H₄) or acetylene (C₂H₂), hydrogen gas, nickel/palladium/platinum catalyst.
• Conditions: Pass the unsaturated hydrocarbon with H₂ over finely divided Ni (Raney Ni) at ~150–300 °C; atmospheric to moderate pressure. Pd/C or Pt also work at lower temperatures.
• Reactions:
  • C₂H₄ + H₂ → C₂H₆.
  • C₂H₂ + 2 H₂ → C₂H₆ (complete hydrogenation).
• Notes: This route is clean and scalable. It is the typical industrial “preparation of ethane by hydrogenation.” Use Lindlar catalyst only if you want to stop at ethene; for ethane use active Ni/Pd/Pt.

5) Alternative coupling for completeness (Corey–House synthesis)

• Chemicals: Methyllithium, copper(I) iodide to form lithium dimethylcuprate (Me₂CuLi), methyl iodide as the partner halide.
• Conditions: Anhydrous ethereal solvent at low temperature under inert gas.
• Reaction: Me₂CuLi + MeI → C₂H₆ + MeCu + LiI.
• Notes: Useful in synthesis teaching; less common for bulk preparation.

How to choose a method

1. Classroom or lab demo: Wurtz reaction is fast and shows coupling clearly.
2. Electrochemistry focus: Pick Kolbe electrolysis of sodium acetate.
3. From carboxylates: Use soda-lime decarboxylation of sodium propionate.
4. From petrochemical feedstocks: Use catalytic hydrogenation of ethene or acetylene.

Safety and purification

• Keep ether and alkali metals strictly dry during Wurtz reactions.
• Vent electrolysis gases safely; remove CO₂ using KOH solution and dry over CaCl₂.
• Hydrogenations require leak-tested setups; purge with inert gas before heating.