Question

An unknown compound A has a molecular formula C₄H₆. When A is treated with an excess of Br₂ a new substance B with formula C₄H₆Br₄ is formed. A forms a white precipitate with ammoniacal silver nitrate solution. A may be

• A. Butyne-1
• B. Butyne-2
• C. Butane-1
• D. Butane-2

Answer 1

The correct option is A

Butyne-1

We know about addition of Halogens.

Addition of Halogen: An alkyne on reaction with bromine water solution or solution of $B{r}_2$ in $CC{l}_4$ gives alkane tetrabromide and the colour of solution disappears.

Since the molecule takes 2 moles of $B{r}_2$. Therefore it is alkyne. Also it gives white ppt with Tollen's reagent therefore acidic H is present. Hence it is 1- Butyne.