1 - AROMATICS (PHENOLS)

Question 1

what is the structure of phenol?

Answer 1

Question 2

what is the pKa of phenol?

Answer 2

10
phenol is a weak acid

Question 3

what are some uses of phenol?

Answer 3

• used to sterilize surgical instruments and clean wounds (it is an antiseptic)
• can be used as an analgesic to relieve minor pain
• corrosive, can cause severe chemical burns
• at low concentrations used to do chemical peels on the skin
• rubber, dyer, perfumes, ink, plastic and epoxy resin (through reactions)

Question 4

structure of BHT (butylated hydroxy toluene) and function

Answer 4

antioxidant food additive

Question 5

structure of salicylic acid and aspirin

Answer 5

Question 6

structure of vanillin and function

Answer 6

flavoring agent

Question 7

where can vanillin like fragments be found?

Answer 7

in lignin
natural constituent of wood, present in cell walls

Question 8

what are the different methyl phenols used for (o,m or p)

Answer 8

constituents of cresote, from coal tar or crude oil
used in disinfectants, deodorizers and insecticides

Question 9

what are benzene diols used for?

Answer 9

film developing agent
disinfectant
reducing agent, film developing, skin whitening agent

Question 10

what are ways in which phenols can be identified?

Answer 10

1. ferric chloride color test
   the solution turns purple when there is phenol prosent
   the iron makes a complex with the phenols
2. in IR, there is the characteristic 3600cm^-1 broad curved stretch, with some interference from the intermolecular H bonding
3. through NMR spectroscopy

Question 11

what are the pKas of alcohols?

Answer 11

16-18
phenol is a stronger acid than other alcohols

Question 12

why is phenol more acidic that other alcohols?

Answer 12

1. resonance effect:
   the phenoxide negative charge can be delocalised throughout the ring, which leads to a more stable conjugate base = more acidic
2. orbital and inductive effects:
   aliphatic alcohols are bound to an sp3 carbon, while on phenol the carbon is sp2
   this increases the s character, and makes it was electron withdrawing, which again leads to greater stabilization

Question 13

what is the pKa of carboxylic acids?

Answer 13

4-5

Question 14

what are the different solubilities of carboxylic acids, phenols and alcohols in strong vs weak bases?

Answer 14

carboxylic acids: soluble in both
phenols: soluble in strong but not in weak
alcohols: soluble in neither

Question 15

what is NaNO2 and HCl a source of?

Answer 15

source of nitrosonium ion (Ntriple bond O+)

Question 16

synthesis of phenol from nitrobenzene

Answer 16

Question 17

how is nitrosonium ion formed?

Answer 17

Question 18

mechanism from aniline to diazonium salt derivative

Answer 18