Question

Describe the halogenation of acetylene gas.

Short answer

Question: Describe the halogenation of acetylene gas with chlorine and provide a step-by-step mechanism for the reaction. Answer: The halogenation of acetylene gas with chlorine occurs in a two-step addition reaction. First, a chlorine atom from the Cl2 molecule bonds with one carbon atom of the acetylene molecule, forming a vinyl chloride intermediate. In the second step, a chloride ion attacks the other carbon of the vinyl chloride intermediate, resulting in the formation of the final product, 1,2-dichloroethene. The balanced chemical equation for this reaction is: C_2H_2 + Cl_2 -> C_2H_2Cl_2

Step-by-step solution

Identify the reactants and products

For the halogenation of acetylene gas, we will consider the reaction with chlorine. The reactants are acetylene (C_2H_2) and chlorine (Cl_2), and the main product is 1,2-dichloroethene (C_2H_2Cl_2).

Write balanced chemical equation

The balanced chemical equation for the reaction is: C_2H_2 + Cl_2 -> C_2H_2Cl_2

Understand the mechanism of the reaction

The halogenation of acetylene occurs in a stepwise manner through an addition reaction. First, a halogen atom is added to one of the carbon atoms in acetylene to form a vinyl halide intermediate. The second halogen atom attacks the other carbon atom, forming the final product, 1,2-dichloroethene.

Describe the first step of the mechanism

In the first step of the halogenation, one of the chlorine atoms from the Cl_2 molecule bonds with one of the carbon atoms of the acetylene molecule, creating a vinyl chloride intermediate. The other chlorine atom becomes a chloride ion (Cl^(-)). The reaction intermediate looks like this: C_2H_2 + Cl_2 -> ClCH=CH + Cl^(-)

Describe the second step of the mechanism

In the second step of the halogenation, the chloride ion attacks the other carbon of the vinyl chloride intermediate, resulting in the formation of the final product, 1,2-dichloroethene: ClCH=CH + Cl^(-) -> C_2H_2Cl_2

Recap the reaction mechanism

The halogenation of acetylene with chlorine occurs in a two-step addition reaction. The chlorine atoms are added across the triple bond of the acetylene molecule, one at a time, leading to the formation of 1,2-dichloroethene.