benzene substituents

Question 1

when do we use NBS

Answer 1

when we want monosubstitution of Br onto the benzylic carbon

Question 2

what is NCS

Answer 2

NBS with Cl instead of Br

Question 3

what is the best way to put a halogen onto the benzylic carbon of a benzene

Answer 3

use NBS or NCS

Question 4

what happens if we react benzyl halides with a strong nucleophile

Answer 4

Sn2 = inversion of chemistry

Question 5

what happens if we do Sn1 on a benzyl halide

Answer 5

we get a racemic mix

Question 6

what do we get when benzylic carbons are oxidized

Answer 6

benzoic acids (R –> carboxylic acid group)

Question 7

what can we use to oxidize

Answer 7

Jones, KMnO4

Question 8

for oxidation of benzylic carbons, what needs to be on the molecule for the reaction to occur

Answer 8

we need benzylic hydrogens

Question 9

what happens if we use a MILD oxidizing agent on a benzylic carbon

Answer 9

we get a ketone or aldehyde

Question 10

how do we get a carboxylic acid from a benzylic carbon

Answer 10

oxidation with a strong ox agent

Question 11

how do we get a ketone from a benzylic carbon

Answer 11

mild oxidation of a toluene

Question 12

how do we get an aldehyde from a benzylic carbon

Answer 12

mild oxidation of anything other than a toluene

Question 13

what do we use to do selective oxidation (ie leaving a terminal OH group alone but reacting a dif. OH group)

Answer 13

we use MnO2 to be selective. OH turns into a ketone, and terminal OH stays the same

Question 14

what two reactions can we do with benzyl ethers

Answer 14

reduction or oxidation

Question 15

what do we get by reducing a benzyl ether

Answer 15

toluene

Question 16

what do we use to reduce benzyl ethers

Answer 16

H2 / Pt

Question 17

what do we get by oxidizing a benzyl ether

Answer 17

benzoic acid

Question 18

what do we use to oxidize benzyl ethers

Answer 18

KMnO4 or Jones

Question 19

how might we produce benzoic acid from a basic benzene ring

Answer 19

pressurize it using CO2

ie use CO2, KHCO3(aq), with pressure

Question 20

how do we convert nitrobenzene (strong deactivator) to aniline (strong activator)

Answer 20

reduction

• clemmensen (Zn, Hg, HCl)
• H2 Pd/C, or Adams, or Raney Ni

Question 21

how do we make an aryl cation

Answer 21

oxidize aniline to get an Arenediazonium salt, and then heat it to get the aryl cation

Question 22

why are arenediazonium salts so useful

Answer 22

they’re the precursors of many products

Question 23

in what position will the sub be added when it reacts with an arenediazonium salt

Answer 23

para

Question 24

what happens when we react an azenediazonium salt with another benzene

Answer 24

forms azo compounds: compounds joined by N=N double bond

Question 25

are phenols acidic or basic

Answer 25

acidic

Question 26

how do we make phenol

Answer 26

oxidize aniline and then put it in heated water

Question 27

T or F: phenol is a good nucleophile

Answer 27

true

Question 28

why is phenol a good nucleophile

Answer 28

deprotonation of the OH group makes it a good nucleophile

Question 29

how can we change the pKa of phenol

Answer 29

by adding substituents onto the ring that change the electron density

Question 30

what sub is on the ring for alkoxybenzenes

Answer 30

OR

Question 31

how do we make alkoxybenzene

Answer 31

react phenol with NaOH to make it a nuc, and then with RX to add the R

Question 32

T or F: the production of alkoxybenzene is concerted

Answer 32

true

Question 33

how do we make a benzene with an ester attached

Answer 33

react phenol with NaOH to make it a good nuc, then with RCOX to make the ester