9.7 Substitution Reactions Teach Us Some Important Lessons

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.