Ch. 8 - Elimination ReactionsSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

What's the difference between a nucleophile and a base? You may already know the answer from before. If not, let me try to refresh your memory. Think Bronsted-Lowry and Lewis. Ring a bell?

Concept #1: Understanding the difference between basicity and nucleophilicity.  

Recall that a Nucleophile is an electron pair donor (Lewis Base), and a Base is a proton acceptor (Bronsted-Lowry Base).

 

While the terms nucleophile and base often mean the same thing, there are some exceptions where basicity and nucleophilicity do not mirror each other.

 

Relative Strength Rules:

  1. A negative charge will always be a stronger nucleophile than its neutral counterpart.
  2. The bulkier the base, the more basic and less nucleophilic it is.
  3. Basicity and nucleophilicity have opposite size trends in polar protic solvents. 
Additional Problems
Which of the following species is the least nucleophilic? A) (CH3)3N B) BF3 C) H2O D) (CH3)3CO- E) CN-
Rank the following nucleophiles according to their increasing nucleophilicity in polar aprotic solvents (weakest nucleophile strongest nucleophile) A. 1, 2, 3 B. 1, 3, 2 C. 2, 3, 1 D. 2, 1, 3 E. 3, 1, 2 F. 3, 2, 1
Rank the following molecules in terms of increasing nucleophilicity in a protic solvent: 1. EtONa 2. EtSNa 3. EtNHNa 4. EtPHNa
Which of the following nucleophiles will require a proton removal step after a substitution reaction?
Which SN2 reaction of each pair would you expect to take place more rapidly in a protic solvent?  
Which SN2 reaction of each pair would you expect to take place more rapidly in a protic solvent?  
Which SN1 reaction of each pair would you expect to take place more rapidly? Explain your answer.  
Which of the following cannot act as nucleophile? a) NH3 b) H2O c) I - d) CH4
Which is the weakest nucleophile?
Which halide ion reacts the fastest with cyclopentyl  p-toluenesulfonate in ethanol/water?
Which reagent in each pair listed here would be the more reactive nucleophile in a polar aprotic solvent? (b) CH3O- or CH3CO2- (-OAc)  
Which reagent in each pair listed here would be the more reactive nucleophile in a polar aprotic solvent? (e) H2O or H3O+  
Which reagent in each pair listed here would be the more reactive nucleophile in a polar aprotic solvent? (g) H2S or HS-  
Which reagent in each pair listed here would be the more reactive nucleophile in a polar aprotic solvent? (h) CH3CO2- (-OAc) or OH -  
The reaction of 1° alkyl halides with nitrite salts produces both RNO 2 and RONO. Account for this behavior.  
Which one is the strongest nucleophile in each catagoy? (a) H2O, H2S, H2Se                                        the strongest: __________________   (b) I‐, Br‐, Cl‐, F‐ in an aprotic solvent              the strongest: __________________
The following is a stepwise synthesis by applying Bronsted‐Lowry (B‐L) and Lewis acid‐base (LA and LB) reactions. Please use electron‐pushing arrows to show this transformation logically.A. Draw compounds C, D, and F in the boxes.B. Circle the correct answer(s) clearly and carefully:Step 1 is:       Bronsted‐Lowry reaction     or     Lewis acid‐base reactionStep 2 is:       Bronsted‐Lowry reaction     or     Lewis acid‐base reactionNucleophile:  A     B     C     D     E     FElectrophile:  A     B     C     D     E     FLewis acid:    A     B     C     D     E     FLewis base:   A     B     C     D     E     F
Which is the strongest nucleophile?
Compare the following reactions and decide which reaction occurs fastest.
What is the name of the following?