Q.How is Alkane prepared from Grignard reagent?

Preparation of Alkanes

Although petroleum and natural gas remain the dominant real-world source, several named laboratory routes build alkanes from smaller/simpler precursors, each useful for a different synthetic situation:

• Catalytic hydrogenation of an alkene or alkyne (H2 over Pt/Pd, or over Ni at 298 K -- the Sabatier-Sendersens reaction) simply saturates the multiple bond.
• Decarboxylation of a sodium carboxylate with soda lime (NaOH + CaO) strips off -COONa as Na2CO3, shortening the chain by exactly one carbon relative to the parent acid.
• Kolbe's electrolytic method electrolyses a sodium/potassium carboxylate; decarboxylation at the anode dimerises two identical alkyl radicals into a symmetrical alkane R-R (so it can only build symmetrical products, and doubles the carbon count of the R group).
• Reduction of a haloalkane with nascent hydrogen (Zn/HCl, Zn/CH3COOH, Zn-Cu/ethanol, or LiAlH4) simply swaps the halogen for H; it works for all haloalkanes except fluorides. …