Write an example of each of the followings: i) Baeyer's test ii) Wurtz reaction

2KMnO₄ (cold, dilute)alkaline medium (KOH)2MnO₂ (brown ppt)+2KOH

i) Baeyer’s test This test detects unsaturation (C=C or C≡C bonds) using cold, dilute alkaline KMnO₄. A purple solution of KMnO₄ is added to the organic compound. If the compound is unsaturated, the purple color decolorizes and a brown precipitate of MnO₂ forms. For example: $$\mathrm{CH}{}_2=\mathrm{CH}{}_2+2\mathrm{KMnO}{}_4+3\mathrm{H}{}_2\mathrm{O}\to \mathrm{HO}-\mathrm{CH}{}_2-\mathrm{CH}{}_2-\mathrm{OH}+2\mathrm{MnO}{}_2+2\mathrm{KOH}$$ Positive result: Decolorization + brown ppt → Unsaturated compound (alkene/alkyne).

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bromoethanebromoethane+2 Nasodium+dry etherheat2 NaBrsodium bromide

ii) Wurtz reaction This reaction couples two alkyl halides (R-X) using sodium metal in dry ether to form a higher alkane (R-R). For example, bromoethane reacts as: $$2\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{Br}+2\mathrm{Na}\to \mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{CH}{}_2\mathrm{CH}{}_3+2\mathrm{NaBr}$$ Procedure:

1. Dissolve bromoethane in dry ether.
2. Add sodium metal and heat gently.
3. A colorless gas (ethane) evolves, which burns with a sooty flame (test for alkanes). Limitation: Only works for primary alkyl halides; tertiary halides give elimination.