Alcohols

• Alcohols


  Organic compounds containing the -OH (hydroxyl) functional group

  
• Classification of alcohols


  • Primary (1°)
  • Secondary (2°)
  • Tertiary (3°)

  
• Primary alcohol


  The (functional) carbon atom that is attached to the -OH group is surrounded by one or no other carbon atoms

  
• Secondary alcohol

  The (functional) carbon atom that is attached to the -OH group is surrounded by two other carbon atoms

  
• Tertiary alcohol

  The (functional) carbon atom that is attached to the -OH group is surrounded by three other carbon atoms

  
• When naming alcohols, identify which carbon atom has the -OH group e.g. propan-1-ol, propan-2-ol

  
• Reactions of alcohols

  1. Combustion (with oxygen)

  2. Halogenation (with PCl5, HCl, KBr/H2SO4, red P/I2)

  3. Dehydration (with conc. H3PO4)

  
• Combustion of alcohols

  Complete combustion produces carbon dioxide and water, they are clean burning and release large amounts of energy
• Halogenation to make chloroalkanes

  1. Chlorination with PCl5 for 1° and 2° alcohols

  2. Chlorination with conc. HCl for 3° alcohols

  
• Halogenation to make bromoalkanes

  Bromination with KBr and 50% conc. H2SO4, then warmed with the alcohol

  
• Halogenation to make iodoalkanes

  Iodination with red phosphorus and iodine
• Dehydration to form alkenes

  Heated with concentrated phosphoric acid, removes water

  
  

  by elimination
• Tertiary alcohols are not easily oxidized due to the large R groups on the tertiary carbon preventing reacting groups

  
• Techniques in preparation and purification of liquid organic compounds

  • Heating under reflux
  • Extraction with solvent using separating funnel
  • Distillation
  • Drying with anhydrous salt
  • Boiling temperature determination
• Tertiary alcohols are not easily oxidized 


  the large R groups on the tertiary carbon prevents the reacting groups. Hence, tertiary alcohols are rather unreactive
• Secondary alcohols can be oxidised to form ketones
• Primary alcohols are oxidised to aldehydes then to carboxylic acids
• The positive tests for aldehydes

  In each ase, the metal ions are reduced and the aldehyde oxidised to the carboxylic acid

  A) Benedict's test

  B) control blue

  C) Positive = red

  D) Fehling's solution

  E) control blue

  F) Positive = red

  G) Tollens test

  H) control clear

  I) Positive = silver mirror

  
• the substitution of chlorine will produce white steamy fumes
• when alcohols and sodium react a pop sound occurs

  the equation:

  alcohol + sodium -> alkoxide + hydrogen
• at room temperature alcohols are liquids
• they have a higher boiling point than alkanes of a similar size due to the hydrogen bonding which occurs between the molecules