An unknown compound ( A) has a molecular formula C4 H6. When (A) is treated with excess of Br2 a new substance (B) with formula C4H6 Br4 is formed. (A) forms a white ppt. with ammoniacal silver nitrate. Compound A is
But-1-yne
A is C4H6
Degree of unsaturation
= No of carbon atoms + 1−12 {No of H atoms + No of halogen atoms - No of Nitrogen atoms}
=4+1−62
=5−3=2
Ammoniacal AgNO3 is Tollen's reagent.
Terminal alkynes
R−C≡CHAgNO3/NH3−−−−−−−−→R−C≡CAg↓
(Whiteppt)
Given compound is a terminal Alkynes.
So only option (A) is appropriate.