Why Are Specific Solvents Chosen for Sn2/Sn1, E2, and E1 Reactions?

[alingy1]

Hi all,
I was looking at the answers in my textbook. They seem to make incongruent choices of solvents.

In e) and j), why choose EtOH and H2O/CH3OH? I would rather choose an aprotic solvent like DMF to better allow Sn2 to occur. Especially with j), there is a lot of competition with E2 because OH- is a strong base and because we are attacking a secondary carbon.

 

[alingy1]

I see this again in k). Secondary carbon attacked: why not add DMF to prevent E2 and get best yield?

 

[Teemo]

Depends on the acidity/basicity of the end product. A reaction proceeds towards the weaker base/acid. If your end products are more acidic or basic than the reactants, it will not occur.

 

[alingy1]

Teemo, I don't see how an unreacting reagent can cause a change in acid base interactions.