Alcohols

Summary

Alcohols are organic compounds characterized by the presence of a hydroxyl group (-OH). They can undergo various reactions such as combustion, substitution, and oxidation, and can be classified based on the number of carbon atoms attached to the hydroxyl group.

• Alcohols — organic compounds with a hydroxyl group (-OH) as the functional group.
  Example: Ethanol (C2H5OH) is a common alcohol used in beverages and as a solvent.
• Primary Alcohols — have one carbon atom directly attached to the carbon bearing the -OH group.
  Example: 1-Propanol (CH3CH2CH2OH) is a primary alcohol.
• Secondary Alcohols — have two carbon atoms directly attached to the carbon bearing the -OH group.
  Example: 2-Propanol (CH3CH(OH)CH3) is a secondary alcohol.
• Tertiary Alcohols — have three carbon atoms directly attached to the carbon bearing the -OH group.
  Example: Tert-butanol ((CH3)3COH) is a tertiary alcohol.
• Combustion — exothermic reaction of alcohols with oxygen producing carbon dioxide and water.
  Example: Ethanol combusts to form CO2 and H2O.
• Substitution — alcohols react with hydrogen halides to form halogenoalkanes.
  Example: Ethanol reacts with HCl to form ethyl chloride.
• Oxidation — primary alcohols oxidize to aldehydes and further to carboxylic acids, secondary alcohols to ketones, and tertiary alcohols do not oxidize.
  Example: Ethanol oxidizes to ethanal and then to ethanoic acid.

Exam Tips

Key Definitions to Remember

• Alcohols: Organic compounds with a hydroxyl group (-OH).
• Primary, Secondary, Tertiary Alcohols: Classification based on carbon atoms attached to the -OH group.
• Combustion: Reaction with oxygen producing CO2 and H2O.
• Substitution: Reaction forming halogenoalkanes from alcohols.
• Oxidation: Conversion of alcohols to aldehydes, ketones, or acids.

Common Confusions

• Confusing primary, secondary, and tertiary alcohols based on the number of -OH groups instead of carbon attachments.
• Misunderstanding the products of oxidation for different types of alcohols.

Typical Exam Questions

• What is the general formula for alcohols?
  CnH2n+1OH
• How do you classify alcohols?
  By the number of carbon atoms attached to the carbon with the -OH group.
• What happens when ethanol is oxidized?
  It forms ethanal and can further oxidize to ethanoic acid.

What Examiners Usually Test

• Ability to write and recognize structural, displayed, and skeletal formulae of alcohols.
• Understanding of the reactions alcohols undergo, such as combustion, substitution, and oxidation.
• Classification of alcohols and predicting reaction products based on their type.