alcohols and phenols

Question 1

what are the physical properties of alcohols
(bp solubility and acidity)

Answer 1

1. bp -higher than corresponding alkanes
   depends on - no. of electrons and degree of branching
2. soluble in water due to ability to for H bonds with water molecules but decreases the more C atoms there are due to hydrophobic nature increasing
3. alc can behave as Bronsted-Lowry acid, donating a proton, but is weaker than water

This is due to the R grp exerting a stronger electron donating inductive effect than the H atom resulting in intensification of negative charge on oxygen so RO- less stable than OH-. Hence RO- formed less readily and POE lies to the left

ROH reversible arrow RO- and H+

Question 2

how to prepare alcohols

Answer 2

1. From alkenes - cold conc H2SO4 (aq) followed by addition of H20 with heat
2. From halogenoalkanes - alc NaOH or KOH and HUR
3. From carboxylic acid - LiAlH4 in dry ether
4. From aldehydes and ketones - LiAlH4 in dry ether, NaBH4 in methanol, H2 Pt or with Ni and heat

Question 3

what reactions do alcohols undergo

Answer 3

• Halogenoalkanes
  PX3, PCl5 and SOCl2 all with heat
• Alkenes
  excess conc H2SO4 and heat
• Redox with reactive metal to give salt
• Carbonyl compounds and carboxylic acids
  K2Cr2O7 and H2SO4 with heating under reflux (heat under immediate distillation for aldehyde)
• Esters with Acyl chlorides and carboxylic acids
  conc H2SO4 and heat for carboxylic acyl no need
• Tri-iodomethane formation
  I2 in NaOH(aq) and heat

overall eqn: RCH(CH3)(OH) + 4I2 + 6OH- —> RCOO- + CHI3 + 5I- + 5H20

Question 4

what are the physical properties of phenols
(bp, solubility and acidity)

Answer 4

1. bp - relatively high due to hydrogen bonding between molecules
2. solubility - relatively soluble as H bonds formed with water are able to overcome H bonds formed between water molecules
3. acidity - is a Bronsted Lowry acid as it can donate protons
   - more acidic than water and alc because p orbital of oxygen overlaps with pi cloud of the benzene ring, resulting in delocalization of negative charge on the oxygen into the ring
   - phenoxide anion is stabilized by charge dispersal and is thus more acidic since this effect is not found in water

Question 5

what reactions do phenols undergo

Answer 5

Redox and electrophilic sub at the benzene ring

1. Salts with reactive metals or acid base
   mono or tri subbed nitrophenol
2. dilute HNO3 for mono and conc for tri
3. mono or tri subbed bromophenol or any halogen
   Br2 in CCl4 solvent for mono and in aq for tri

Question 6

how to test for phenol

Answer 6

phenol reacts with neutral FeCl3 to form a violet coloration

Question 7

does alc react with NaOH

Answer 7

no