Exam 3 Study Guide

Question 1

Why are strong activators the way that they are?

Answer 1

• lone pair adjacent to the aromatic ring
• Donates electrons into the ring

Question 2

Why are moderate activators the way that they are?

Answer 2

• lone pair adjacent to the aromatic ring, part of a separate conjugation (NOT with the aromatic ring)

Question 3

Why are weak activators the way that they are?

Answer 3

• no lone pairs adjacent to the ring
• supplies electron density through hyperconjugation (relatively weak)

Question 4

Why are weak deactivators the way that they are?

Answer 4

• weakly deactivated due to induction of electrons OUT of the ring.
  (ortho-para directing due to favorable resonance in the sigma complex)

Question 5

Why are moderate deactivators the way that they are?

Answer 5

• resonance structures place positive charge inside aromatic ring
• no lone pair beside ring

Question 6

Why are strong deactivators the way that they are?

Answer 6

• resonance structures and induction strongly pull electron density from ring

Question 7

What happens in Friedel-Crafts Alkylation?

Answer 7

• alkyl halide serves as an electrophile with assistance from catalyst

Question 8

What happens in Friedel-Crafts Acylation?

Answer 8

forms a new carbon-carbon bond, like alkylation, but includes acyl group

Question 9

Why is the acylium ion good for the activation of an acyl group

Answer 9

• its a good electrophile and is resonance stabilized

Question 10

Why is the methyl group ortho/para directing?

Answer 10

because the in the meta sigma complex the carbocation is never near the methyl group

Question 11

Why are nitro groups meta-directing?

Answer 11

the sigma complex of ortho/para attacks are destabilized

Question 12

Why are nitro groups deactivating substituents?

Answer 12

• they withdraw electrons from the benzene ring via resonance and inductively

Question 13

Why are methoxy groups (ether) activating groups?

Answer 13

they donate electrons via resonance and have addition resonance structures

Question 14

How do you determine the number of pi electrons of an aromatic heterocycle?

Answer 14

• if N is bound to hydrogen then count lone pair as part of the ring
• if not, don’t count electrons