A free radical substitution reaction between ethane and bromine produces bromoethane as the main product.
Explain what is happening at each stage of the reaction.
Also INCLUDE equations related to EACH stage of the reaction (the equations are a part of your explanation).
Consider the three stages involved:
initiation, propagation, and termination.
In a free radical substitution reaction between ethane and bromine, bromoethane is the main product formed. This reaction occurs in three main stages: initiation, propagation, and termination. Let's explore each stage along with the corresponding equations.
1. Initiation:
The initiation stage involves the generation of free radicals, which are highly reactive species with unpaired electrons. In this case, bromine molecules (Br2) are commonly used to initiate the reaction. The process typically occurs under ultraviolet (UV) light or high temperatures, as it requires energy to break the relatively weak bromine-bromine bond. This homolytic cleavage generates two bromine free radicals.
Equation: Br2 → 2 Br•
2. Propagation:
In the propagation stage, the free radicals react with the starting material (ethane) and generate new free radicals, leading to a chain reaction. For ethane and bromine, there are two possible propagation steps:
a. Bromination of Ethane:
One bromine free radical reacts with a hydrogen atom from ethane, replacing it with a bromine atom.
Equation: C2H6 + Br• → C2H5• + HBr
b. Recombination of Ethyl Radical and Bromine:
The ethyl radical (C2H5•) formed from the previous step reacts with a bromine molecule (Br2), yielding bromoethane and regenerating a bromine free radical to continue the reaction.
Equation: C2H5• + Br2 → C2H5Br + Br•
Note: The propagation steps can occur multiple times, with each new free radical generated initiating another round of propagation.
3. Termination:
The termination stage involves the removal of free radicals to stop the chain reaction. Termination can occur through various reactions, such as recombination of two free radicals or reaction with an impurity or solvent. Here are a few examples:
a. Recombination of Two Bromine Free Radicals:
Two bromine free radicals combine to form a bromine molecule, terminating the reaction.
Equation: 2 Br• → Br2
b. Recombination of Ethyl Radical and Bromine:
The ethyl radical reacts with the bromine free radical, resulting in the formation of bromoethane and stopping the chain reaction.
Equation: C2H5• + Br• → C2H5Br
Note: Termination steps can help control the reaction to prevent excess radical formation and minimize side product formation.
By understanding the different stages of the reaction (initiation, propagation, and termination) and the associated equations, we can obtain bromoethane as the primary product of the free radical substitution reaction between ethane and bromine.