Chapter 5: 5.6 Solvent Effects in Substitution Reactions

Question 1

Why could a solvent have a big effect on the SN1 and SN2 reaction?

Answer 1

Both reactions proceed through either a transition state or intermediate (or both!)

Question 2

Describe:

Transition states of SN2 reactions

Answer 2

SN2 reactions have high-energy transition states which carry partial charges

Question 3

What is the best solvent for transition states in SN2 reactions?

Answer 3

Use polar solvents without protons
* There are strong nucleophiles present

Question 4

What is a polar solvent without protons known as?

Answer 4

Polar aprotic solvent

Question 5

List:

Examples of Polar Aprotic Solvents

Answer 5

• Acetone
• Demthylsulfoxide (DMSO)
• Dimethylformamide (DMF)
• Hexamethylphosphoramide (HMPA)

Question 6

Describe:

The transition states of SN1 reactions

Answer 6

SN1 reactions have arbocation intermediates which carry formal positive charges

Question 7

What is the best solvent for transition states in SN1 reactions?

Answer 7

Use polar solvents with protons
* There are weak nucleophiles present

Question 8

What are polar solvents with protons known as?

Answer 8

Polar protic solvent

Question 9

List:

Examples of Polar Protic Solvent

Answer 9

• Water (H2O)
• Alcohols (ROH, usually MeOH or EtOH)
• Amines (usually NH3)
• Carboxylic acids (RCOOH, usually acetic acid)