32 Hydroxy Compounds

32.1 Alcohols:

  1. Reaction with Acyl Chlorides to Form Esters:
    1. Alcohols can react with acyl chlorides (acid chlorides) to form esters.
    2. The reaction is typically carried out in the presence of a base, such as pyridine, to neutralize the hydrogen chloride (HCl) byproduct.
    3. The general reaction equation is: R-OH + R'-COCl → R'-COOR + HCl
    4. An example is the reaction between ethyl alcohol (ethanol) and ethanoyl chloride (acetyl chloride) to form ethyl ethanoate (ethyl acetate): CH3CH2OH + CH3COCl → CH3COOCH2CH3 + HCl

32.2 Phenol:

  1. Production of Phenol:
    1. Phenol can be produced by the reaction of phenylamine (aniline) with nitrous acid (HNO2) or sodium nitrite (NaNO2) in the presence of dilute acid below 10°C.
    2. This reaction leads to the formation of the diazonium salt, which is then further warmed with water (H2O) to yield phenol.
  2. Chemistry of Phenol:
    1. Phenol exhibits various characteristic reactions, including:

(a) Reacting with bases, such as sodium hydroxide (NaOH(aq)), to produce sodium phenoxide.

(b) Reacting with sodium metal (Na(s)) to produce sodium phenoxide and hydrogen gas (H2(g)).

(c) Reacting with diazonium salts in alkaline conditions to form azo compounds. (d) Undergoing nitration of the aromatic ring with dilute nitric acid (HNO3(aq)) at room temperature to give a mixture of 2-nitrophenol and 4-nitrophenol.

(e) Undergoing bromination of the aromatic ring with bromine water (Br2(aq)) to form 2,4,6-tribromophenol.

  1. Acidity of Phenol:
    1. Phenol is acidic in nature due to the presence of the hydroxyl group (-OH) attached directly to the aromatic ring.
    2. The hydroxyl group can donate a proton (H+) to form a phenoxide ion (C6H5O-) in the presence of a base.
  2. Relative Acidities of Water, Phenol, and Ethanol:
    1. Phenol is more acidic than water and ethanol due to the resonance stabilization of the phenoxide ion.
    2. The delocalization of the negative charge across the aromatic ring in phenoxide makes it more stable and facilitates proton donation.
  3. Differences in Nitration and Bromination of Phenol:
    1. The reagents and conditions for the nitration and bromination of phenol differ from those for benzene due to the presence of the hydroxyl group in phenol.
    2. Phenol is more reactive than benzene towards electrophilic substitution reactions because the hydroxyl group activates the aromatic ring and directs substitution to the ortho and para positions.
  4. Directing Effects of the Hydroxyl Group in Phenol:
    1. The hydroxyl group in phenol directs substitution reactions to the ortho (2-), para (4-), and occasionally meta (3-) positions on the aromatic ring.
  5. Application to Other Phenolic Compounds:
    1. Similar reactions and principles can be applied to other phenolic compounds, such as naphthol, which exhibit similar reactivity patterns.