In the laboratory, ethylene and acetylene can be distinguished by using
- ABr
2
/H
2
O - BKMnO
4
/OH
⊖
/H
2
O - CTollens' reagent
- DFehling's solution
Solution & Step-by-step Explanation
Both ethylene (C
2
H
4
, an alkene) and acetylene (C
2
H
2
, an alkyne) are unsaturated hydrocarbons, so they will both give positive test results by decolorizing Bromine water (Br
2
/H
2
O) and Baeyer's reagent (KMnO
4
/OH
⊖
).
However, acetylene is a terminal alkyne containing acidic hydrogen atoms (H−C≡C−H). It reacts with ammoniacal silver nitrate (Tollens' reagent) to form a distinctive white precipitate of silver acetylide (Ag−C≡C−Ag). Ethylene does not react with Tollens' reagent because it lacks terminal acidic acetylenic hydrogens.
2
H
4
, an alkene) and acetylene (C
2
H
2
, an alkyne) are unsaturated hydrocarbons, so they will both give positive test results by decolorizing Bromine water (Br
2
/H
2
O) and Baeyer's reagent (KMnO
4
/OH
⊖
).
However, acetylene is a terminal alkyne containing acidic hydrogen atoms (H−C≡C−H). It reacts with ammoniacal silver nitrate (Tollens' reagent) to form a distinctive white precipitate of silver acetylide (Ag−C≡C−Ag). Ethylene does not react with Tollens' reagent because it lacks terminal acidic acetylenic hydrogens.