Chapter 17: N.A.S / Allylic and Benzyllic Reactivity

Question 1

Criteria for N.A.S.

Answer 1

1. There must be an e- withdrawing group on the ring
2. There must be a leaving group on the ring
3. The LG must be ortho or para to the EWG

Question 2

Good leaving groups

Answer 2

Question 3

electron-withdrawing groups

Answer 3

Question 4

S_NAr Mechanism of N.A.S.

Answer 4

1. nucleophile attacks the ring (at the location of the LG) to generate meisenheimer complex (resonance structures)
2. loss of LG to restore aromaticity
3. deprotonation and reprotonation

Question 5

Elimination-addition method of N.A.S.

Answer 5

• occurs when LG present but no EWG
• only occurs at very high temps
• steals hydrogen and create triple bond where LG is, kicking off LG
• nuclephile attacks at either side of triple bond, resulting in mix of products

Question 6

Synthesizing Phenol

Answer 6

Question 7

Synthesizing aniline

Answer 7

Question 8

How do you decide which mechanism it follows?

Answer 8

Question 9

Answer 9

Benzyllic Hydrogens

Question 10

Answer 10

Allylic Hydrogens

Question 11

Bromination with benzyllic hydrogens

Answer 11

• proceeds via radical mechanism

Question 12

Bromination with allylic hydrogens

Answer 12

Question 13

Primary alcohols are oxidized to ___

Answer 13

aldehydes

Question 14

Secondary alcohols are oxidized to ____

Answer 14

ketones

Question 15

Oxidizing alcohols

Answer 15

• MnO4 for both allylic and benzyllic hydrogens and for both primary and secondary alcohols

Question 16

Side chain oxidation of alkyl benzenes

Answer 16

-any length alkyl group will be reduced to carboxylic acid

Question 17

Allylic and benzyllic groups stabilize:

Answer 17

• carbocations
• anions
• radicals