Substitution and Elimination

SN1, SN2, E1, E2 Review

Substitution

Substitution or Elimination RXN?

nucleophile replaces halogen

Elimination

Substitution or Elimination RXN?

Double bond (alkene) is formed

• use of a base

bases; acids

Good leaving groups are conjugate ________ of strong _____.

Strong

Strong or weak nucleophiles?

• I^-

• Br^-

• Cl^-

• HS^-

• HO^-

• N≡C^-

• RO^-

Weak

Strong or weak nucleophiles?

• H₂O

• ROH

Configuration flips

SN2:
if the α position is a chiral center, what happens to the configuration?

Methyl >1° > 2° > 3°

SN2:

Rank the following from most to least reactive:

Methyl, 1°, 2°, 3°

Methyl

In an SN2 reaction, what is most reactive?
Methyl, 1°, 2°, 3°

Good leaving groups

Are the following are considered good leaving groups or bad leaving groups?

Recall: Good leaving groups are conjugate bases of strong acids

Bad leaving groups

Are the following considered good leaving groups or bad leaving groups?

Recall: Good leaving groups are conjugate bases of strong acids

1,2-elimination

a proton is removed from the β position, the halide leaves from the α position, and a double bond forms between α and β positions

Zaitsev

Zaitsev or Hoffman?

favors the more substituted alkene

Hoffman

Zaitsev or Hoffman?

favors the less substituted alkene

polar aprotic solvents

SN2 favors polar protic or polar aprotic?

Polar aprotic solvents

Protic or aprotic solvents?

Protic solvents

Protic or aprotic solvents?

Hofmann

What is the major product?

A sterically hindered product

Zaitsev

What is the major product?

A not sterically hindered product