A hydrocarbon, 'X' (C3H4) decolourises Br2/CCl4 solution forming 'Y'. 'X' gave a red precipitate of a compound 'Z' with ammoniacal cuprous chloride. X, Y, and Z respectively are:
A
CH2=C=CH2,CH2Br−CBr2−CH2Br,CH3−C≡C−Cu+
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B
CH3−C≡CH,CH3−CBr2−CHBr2,CH3−C≡C−Cu+
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C
CH3−C≡CH,CH3−CBr=CHBr,Cu+CH−2−C≡CH
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D
CH2=C=CH2,CH2Br−CH=CHBr;CH3−C≡C−Cu+
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Solution
The correct option is BCH3−C≡CH,CH3−CBr2−CHBr2,CH3−C≡C−Cu+ The molecular formula of compound 'X' is C3H4. It decolourises bromine solution and it gives red precipitate when reacts with ammoniacal cuprous chloride. This confirms the presence of terminal alkyne which has acidic proton. The only possible structure with molecular formula C3H4 for terminal alkyne is CH3−C≡CH (X).
When bromine is treated with alkyne in CCl4, they gets added to alkyne to give 1, 1, 2, 2-tetrabromo propane (Y).
When 1-propyne (X) react with ammoniacal cuprous chloride it gives copper acetylide.