Preparation of Hydroxyl Compounds

Preparation of hydroxyl compounds

Preparation of alcohols

i. Reaction between moist silver oxide and haloalkane

Alcohols can be prepared by the reaction of moist silver oxide (Ag₂O) with haloalkanes:

R-X + Ag₂O + H₂O → R-OH + AgX

Example:

C₂H₅Br + Ag₂O + H₂O → C₂H₅OH + AgBr

ii. Reaction between haloalkane and alkaline solution

Haloalkanes react with alkaline solutions like NaOH or KOH to produce alcohols:

R-X + NaOH → R-OH + NaX

Example:

C₂H₅Cl + NaOH → C₂H₅OH + NaCl

iii. Acidic hydrolysis of alkenes

Alkenes react with water in the presence of sulfuric acid to form alcohols:

R-CH=CH₂ + H₂O → R-CH(OH)-CH₃

Example:

CH₂=CH₂ + H₂O → CH₃CH₂OH

iv. Reduction of carbonyl compounds

Carbonyl compounds react with reducing agents to form alcohols:

• Aldehydes: Give primary alcohols. R-CHO + 2[H] → R-CH₂OH

  

• Ketones: Give secondary alcohols. R-CO-R' + 2[H] → R-CH(OH)-R'

  

v. Reduction of carboxylic acids

Carboxylic acids react with strong reducing agents like LiAlH₄ to produce primary alcohols:

R-COOH + 4[H] → R-CH₂OH + H₂O

Example:

CH₃COOH + 4[H] → CH₃CH₂OH + H₂O

Note: If a weak reducing agent is used or the amount of reducing agent is limited, aldehydes are formed instead of alcohols.

vi. Reaction between Grignard reagent and carbonyl compounds

Grignard reagents react with carbonyl compounds followed by acidic hydrolysis to form alcohols:

• If the carbonyl compound is formaldehyde (HCHO), a primary alcohol is formed. RMgX + HCHO → RCH₂OMgX → RCH₂OH

  

• If the carbonyl compound is an aldehyde (except formaldehyde), a secondary alcohol is formed. RMgX + R'-CHO → R-CH(OH)-R'

  

• If the carbonyl compound is a ketone, a tertiary alcohol is formed. RMgX + R'COR" → R-C(OH)-R'-R"