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9.7 Substitution Reactions Teach Us Some Important Lessons
The primary tells us that it needs to be an S 2 pathway.
We have a strong nucleophile, which favors S 2.
N doesn't give us much.
The solvent isn't indicated.
We think that the reaction follows an S 2 mechanism.
To determine if the reaction will proceed via an S 2 or an S 1 pathway, look at all of the reagents and conditions.
Almost the same products are produced by S 1 and S 2 reactions.
The leaving group is attached to a stereo center.
The outcome of S 1 and S 2 processes are different.
When carbocation rearrangements are possible, this difference can be significant.
S 2 reactions are not.
Valuable lessons will be important as we move forward.
All of the relevant information is contained within the mechanisms.
Everything else can be justified based on the mechanisms.
The factors that influence the reaction are summarized in the mechanism.
Every reaction you will see from now on is true.
You have practiced thinking this way.
When analyzing a reaction, there are multiple factors at play.
Sometimes the factors are pointing in the same direction while other times they are in conflict.
When they are in a conflict, we need to weigh them against each other in order to determine the path of the reaction.
A theme in organic chemistry is the concept of competing factors.
If we analyze the first factor, we will find two effects: steric and electronic considerations.
Because of steric considerations, the S 2 reactions need a primary or secondary sub N to attack a tertiary substrate.
For S 1 reactions, electronic considerations were of paramount importance.
The alkyl groups were needed to stable the carbocation.
steric and electronic effects are major themes in organic chemistry.
The rest of the course can be explained with either an electronic or steric argument.
The better off you will be, the sooner you learn to consider these two effects.
The electronic effects are more complex than the steric effects.
The other three factors that we saw were electronic arguments.
You will begin to see common threads in all of the reactions that you will encounter in this course once you get the hang of the electronic arguments.
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