Different reactions (free radical, competitive etc.) Flashcards
What is a competitive reaction?
Reactions that are parallel
What is the yield of a competitive reaction worked out by?
Using the rate constants
When working out the yield of a competitive reaction, what goes on the bottom of the equation and what goes on the top?
Top - the rate constant of the steps that lead to the product
Bottom - the rate constant of the steps that lead to the product and the rate constant of the competitive steps
What is important in a competitive reaction?
The use of a catalyst to control product distribution
What is there a need for in competitive reactions?
Need to eliminate side reactions
What is there no need for in competitive reactions?
No need to be fast as it all depends on the relative rates
What could have important effects when looking at competitive reactions?
Temperature
If we have different EA terms
What is the effect of a catalyst?
To lower the activation energy at a specific temperature
What is a consecutive reaction?
The reactants form an intermediate species, which subsequently reacts to form the product
What does the ability to observe the intermediate depend on?
The relative rates for its formation and decay
What are the three parts of a graph for a consecutive reaction where A -> I -> B?
- Decay of the reactant A
- Growth and subsequent decay of the intermediate
- Appearance of the product B
In the reaction A -> i -> B, what does the rate constant KAI lead to?
Increase in the concentration of the intermediate
In the reaction A -> i -> B, what does the rate constant KIB lead to?
Decrease in the concentration of the intermediate
Write the differential equation for the intermediate species in consecutive reactions?
d[I]/dt = KAI [A] - KIB [I]
What is best to focus on in consecutive reactions?
Better to focus the attention on the behaviour of the intermediate
For consecutive reactions, which rate constant will be the bottleneck if KIB»_space; KAI?
KAI will be the bottleneck
For consecutive reactions, which rate constant will be the bottleneck if KAI»_space; KIB?
KIB will be the bottleneck
What is equal to the initial concentration of [A] in consecutive reactions?
[A] + [I] + [B]
In consecutive reactions, how can you work out the time for the intermediate to reach maximum concentration?
Differentiate
[I] = KAI/KIB - KAI (e⁻ᴷᴬᴵᵀ - e⁻ᴷᴵᴮᵀ) [A]₀
What is the differentiated equation for working out the time taken for the intermediate to reach the maximum concentration?
t = (1 / KAI - KIB) ln (KAI / KIB)
What is a chain reaction a type of?
Consecutive reactions
What is a chain reaction?
An intermediate produced in one step reacts to form a reactive intermediate in a subsequent step.
This repeats
What are intermediates known as in a chain reaction?
Chain carrier
What do chain reactions mostly involve?
Free radicals formed by breaking a bond to generate species with unpaired electrons
