Alcohols can be prepared in several ways:

1. Hydration of alkenes:
   CH₂=CH₂ + H₂O → CH₃CH₂OH (in presence of acid catalyst).

2. Reduction of carbonyl compounds:
   Aldehydes → primary alcohols; ketones → secondary alcohols.
   Example: CH₃CHO + H₂ → CH₃CH₂OH.

3. Substitution of alkyl halides:
   R–Br + NaOH → R–OH + NaBr.

4. Reduction of carboxylic acids or esters:
   RCOOH + LiAlH₄ → RCH₂OH.

5. Fermentation of sugars (natural method):
   C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (using yeast enzymes).