Section 8.1: Introduction to the nucleophilic substitution reaction

Section 8.2: Two mechanistic models for a nucleophilic substitution reaction

1. Associative nucleophilic substitution: the S_N2 reaction
2. Dissociative nucleophilic substitution: the S_N1 reaction
3. Nucleophilic substitutions occur at sp³-hybridized carbons

Section 8.3: More about nucleophiles

1. What makes a nucleophile?
2. Protonation states and nucleophilicity
3. Periodic trends and solvent effects in nucleophilicity
4. Resonance effects on nucleophilicity
5. Steric effects on nucleophilicity

Section 8.4: Electrophiles and carbocation stability

1. Steric effects on electrophilicity
2. Stability of carbocation intermediates

Section 8.5: Leaving groups and solvent effects

1. What makes a good leaving group?
2. Leaving groups in biochemical reactions
3. Synthetic parallel - conversion of alcohols to alkyl halides, tosylates and mesylates
4. S_N1 or S_N2?  Predicting the mechanism

Section 8.6: Epoxides as electrophiles in nucleophilic substitution reactions

1. Epoxide structure
2. Epoxide ring-opening reactions - S_N1 vs S_N2, regioselectivity, and stereoselectivity

Section 8.P:  Problems for Chapter 8

In this chapter, we will extend our discussion, begun in chapter 6, of those organic reactions commonly known as 'nucleophilic substitutions'.  In doing do, we will have an opportunity to consider in greater detail the various factors affecting the three main players in most organic reaction mechanisms: the nucleophile, the electrophile, and the leaving group.  We will also see, for the first time, how stereochemical concepts are applied to the analysis of an organic reaction.

As we tackle this new and challenging chemistry, it is very important to keep in mind the central ideas that we learned in the acid-base chapter about electron density and how it is stabilized.  At that time, we were talking about the breaking and forming of bonds to acidic hydrogens.  Now, we will extend our discussion to reactions involving bonds between heteroatoms and carbon - but for much of what concerns us in this chapter, all of the fundamental ideas we’ve learned about electron density still apply!

Contributors

• Organic Chemistry With a Biological Emphasis by Tim Soderberg (University of Minnesota, Morris)

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