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).
The three stages involved have to be considered:
initiation, propagation, and termination.
In a free radical substitution reaction between ethane (C2H6) and bromine (Br2), the bromoethane (C2H5Br) is formed as the main product. This reaction occurs via three stages: initiation, propagation, and termination.
1. Initiation:
In this stage, the reaction is initiated by the formation of free radicals. Free radicals are highly reactive species with unpaired electrons. In this case, the initiation step involves the homolytic cleavage of the bromine molecule (Br2) to generate two bromine radicals (Br•) through the breaking of the weak Br-Br bond:
Br2 → 2Br•
2. Propagation:
In the propagation stage, the bromine radicals react with ethane (C2H6) to form bromoethane (C2H5Br) and regenerate more radicals which can continue the reaction. There are two propagation steps involved in this reaction:
Step 1:
Br• + C2H6 → C2H5• + HBr
Step 2:
C2H5• + Br2 → C2H5Br + Br•
In step 1, a bromine radical (Br•) reacts with ethane to form an ethyl radical (C2H5•) and hydrogen bromide (HBr) is released. The ethyl radical formed in step 1 then reacts with another molecule of bromine (Br2) in step 2 to regenerate a bromine radical (Br•) and form the desired product bromoethane (C2H5Br).
3. Termination:
The termination step involves the termination of the radical chain reaction by the combination of two radicals. This step occurs when two radical species collide and form a stable molecule, thereby stopping the chain reaction. There are several possible termination steps in this reaction. Here are two examples:
Example 1:
C2H5• + Br• → C2H5Br
Example 2:
C2H5• + C2H5• → C4H10
These termination steps involve the combination of the carbon-centered ethyl radical (C2H5•) with either a bromine radical (Br•) or another ethyl radical (C2H5•) to form either bromoethane (C2H5Br) or butane (C4H10).
Overall, the three stages of the free radical substitution reaction between ethane and bromine involve initiation through the homolytic cleavage of the bromine molecule, propagation through a series of radical reactions, and termination through the combination of radicals.