Question

An unknown compound A has a molecular formula `C_4H_6`. When A is treated with excess to `Br_2` a new substance B with formula `C_4H_6Br_4` is formed. A forms a white precipitate with ammoniacal silver nitrate solution A may
A. but-1-yne
B. but-2-yne
C. but-1-ene
D. but-2-ene

Answer 1

Correct Answer - A
Molecular formula `C_4H_6` corresponds to `C_(n)H_(2n-2)`. Thus comound A must be an alkyne. It is a terminal alkyne as it forms a white precipitate with ammoniacal silver nitrate solution.
`CH_3CH_2CBr_2CHBr_2underset(excess)overset(Br_2)toCH_3CH_2C-=CHoverset(Ag(NH_3)_2^(+)overline(O)H)toCH_3CH_2C-=CAg`