The reaction of ethyne (C₂H₂) with bromine (Br₂) in carbon tetrachloride (CCl₄) is a halogenation reaction where bromine adds across the triple bond of ethyne.

Here's the balanced chemical equation:

C₂H₂ + 2Br₂ → Br₂CH-CHBr₂

Explanation:

* Ethyne (C₂H₂): This is the starting alkene with a triple bond.

* Bromine (Br₂): The halogen that reacts with ethyne.

* Carbon tetrachloride (CCl₄): This acts as a solvent, allowing the reaction to occur smoothly and preventing the formation of unwanted side products.

* 1,1,2,2-tetrabromoethane (Br₂CH-CHBr₂): This is the product formed by the addition of two bromine molecules across the triple bond of ethyne.

Mechanism:

The reaction proceeds in a stepwise manner, with the initial formation of a bromonium ion intermediate:

1. Electrophilic attack: The bromine molecule is polarized by the electron cloud of the triple bond in ethyne, leading to the formation of a bromonium ion.

2. Nucleophilic attack: The bromide ion (Br⁻) then attacks the bromonium ion, opening the ring and forming the final product, 1,1,2,2-tetrabromoethane.

Note:

The reaction occurs in the presence of a catalyst, like iron (Fe), which enhances the rate of reaction by helping to break the Br-Br bond.