Q.Complete the following equation:

Ethylene + Baeyer's reagent (cold dilute alkaline KMnO4) gives ethylene glycol.

Baeyer's reagent test is a classic test for unsaturation (C=C or C≡C bonds). When ethylene (CH2=CH2) is treated with cold, dilute, alkaline potassium permanganate solution, the purple colour of KMnO4 fades (decolourises) as the alkene is oxidised. Mechanistically, the reagent adds two -OH groups across the double bond (syn-addition, via a cyclic manganate ester intermediate), converting the C=C into a vicinal diol:

CH2=CH2 + [O] + H2O → CH2(OH)-CH2(OH) (ethylene glycol)

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Ethylene (C2H4), having a C=C double bond, decolorizes alkaline KMnO4 (Baeyer's test for unsaturation); the saturated compounds do not.

Baeyer's reagent (cold, dilute, alkaline KMnO4) oxidizes carbon–carbon double/triple bonds (e.g., converting an alkene to a diol), and in doing so the purple permanganate ion is reduced and decolorized (to brown MnO2). C3H8 (propane), CH4 (methane), and CCl4 (carbon tetrachloride) are all saturated (or fully substi …

Alkaline KMnO4 (Baeyer's reagent) turns ethylene into ethylene glycol.

Cold, dilute alkaline potassium permanganate is Baeyer's reagent, used as a test for unsaturation. It syn-adds two hydroxyl groups across the double bond of an alkene. With ethylene (CH2=CH2):

CH2=CH2 + [O] + H2O -> CH2(OH)-CH2(OH)

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Ethylene + cold alkaline KMnO₄ → ethylene glycol — option (b).

From NCERT Class 11 Chemistry (Hydrocarbons): cold, dilute alkaline KMnO₄ (Baeyer's reagent) carries out syn-dihydroxylation of a double bond:

CH₂=CH₂ + H₂O + [O] →(cold dil. alkaline KMnO₄) HOCH₂–CH₂OH. …

Hot alkaline KMnO4 cleaves ethene's double bond completely, oxidising both terminal =CH2 carbons all the way to CO2.

Cold, dilute alkaline KMnO4 (Baeyer's reagent) adds across a C=C double bond to give a 1,2-diol (glycol) without breaking the carbon skeleton. But under HOT, stronger alkaline KMnO4 conditions (as indicated here by the elevated temperature, 373-383 K, and 4 atoms of oxygen supplied), the oxidation goes further and actually cleaves the C=C bond:

• If a doubly-bonded carbon carries one H and one alkyl group (=CHR), it is oxidised to a carboxylic acid (RCOOH).
• If a doubly-bonded carbon carries two alkyl groups (=CR2), it is oxidised to a ketone (R2C=O).
• If a doubly-bonded carbon is a TERMINAL =CH2 group (two H atoms, as in ethene), it is oxidised all the way to CO2 (with H2O). …