ORGANIC CHEMISTRY CHAPTER 11

Nucleophilic substitution

Reaction where a nucleophile replaces a leaving group

SN2 reaction

One-step substitution with backside attack and inversion of configuration

Backside attack

Nucleophile attacks opposite side of leaving group in SN2

Inversion of configuration

Flip in stereochemistry during SN2 reaction

SN2 rate law

Rate depends on substrate and nucleophile concentration

SN2 favored conditions

Primary substrate

Steric hindrance

Crowding that slows or prevents reactions like SN2

SN1 reaction

Two-step substitution involving carbocation intermediate

Carbocation intermediate

Positively charged carbon formed in SN1/E1 reactions

SN1 rate law

Rate depends only on substrate concentration

SN1 favored conditions

Tertiary substrate

Racemization

Formation of mixture of stereoisomers in SN1

Carbocation rearrangement

Shift (hydride or alkyl) to form more stable carbocation

Elimination reaction

Reaction that forms a double bond by removing atoms

Zaitsev’s rule

More substituted alkene is the major product

E2 reaction

One-step elimination where base removes proton as leaving group leaves

Anti-periplanar geometry

Required alignment for E2 reaction (H and leaving group opposite)

E2 favored conditions

Strong base

E1 reaction

Two-step elimination via carbocation intermediate

E1 characteristics

Competes with SN1 and forms more substituted alkene

E1cB reaction

Elimination via carbanion intermediate with poor leaving group

Strong base

Species that removes protons (favors elimination)

Strong nucleophile

Species that donates electrons to carbon (favors substitution)

Polar protic solvent

Solvent that stabilizes carbocations (favors SN1/E1)

Polar aprotic solvent

Solvent that enhances nucleophile strength (favors SN2)

Competition (SN vs E)

Outcome depends on substrate

Heat effect

Higher temperature favors elimination over substitution