Chapter 22: Chemistry of Benzene Substituents

Question 1

Complete Benzylic Oxidation of Alkyl Chains

Answer 1

cleave benzylic C-C bonds to create aromatic ketones and acids

1. KMnO4, HO-, Δ
2. H+, H2O

Question 2

1. KMnO4, HO-, Δ

2. H+, H2O

Answer 2

benzylic ketones

Ph-CH3 => Ph-COOH

Question 3

MnO2, acetone, 25°C, 5 h

Answer 3

benzylic ketone formation

Question 4

Selective Oxidation of Benzylic Alcohol

Answer 4

MnO2, acetone, 25°C, 5 h

Question 5

Hydrogenolysis

Answer 5

cleavage of benzylic esters

H2, Pd-C, 25°C

Question 6

Nucleophilic Aromatic Subsitution

Answer 6

may follow an addition/elimination pathway

has a strong e-witthdrawing group located ortho or para to the LG which stabilize the anion by resonance

Question 7

Ipso Substitution

Answer 7

replacing a group other than a hydrogen on an aromatic ring

Question 8

Nucleophilic Aromatic Subsitution Mechanism

Answer 8

1. addition (Nu attacks ipso position, anion created at adjacent carbon on benzene), rate determining step, has many possible resonance structures
2. elimination of LG to regenerate aromatic ring

Question 9

Na2CO3, HOH, 100°C

Answer 9

replace Cl with OH

Question 10

1. NaOH, H2O, 340°C, 150 atm

2. H+, H2O

Answer 10

making phenol from haloarenes (ex: chlorobenzene)

half of product is substituted at ipso position, half at adjacent carbon (uses a benzyne intermediate)

Question 11

1. KNH2, liquid NH3

2. H+, H2O

Answer 11

making benzenamine (aniline) from haloarenes

Question 12

Benzyne

Answer 12

has a highly strained triple bond in a benzene ring that is very reactive
exists only as an intermediate and is rapidly attacked by nucleophiles

Question 13

NaNO2, H+, H2O, 0°C

Answer 13

making N2 from NH2, N2 is a super LG and in water a phenol will be made

Question 14

Sandmeyer Reaction

Answer 14

starting from benzene

1. HNO3, H2SO4
2. reduction
3. NaNO2, H+
4. NaOH, H2O