Alcohols and carboxylic acids

• What is the general formula for an alcohol?

  CnH2n+1_OH

  
• What is the functional group for alcohols?

  OH (hydroxyl group).
• If you heat an alcohol and add an acid catalyst, an alkene and water would be formed. This is called a dehydration reaction because the hydroxyl functional group has been removed from the alcohol.
• What is the practical method for alcohol combustion?

  1. Measure mass of spirit burner and fuel with a balance.
  2. Add 100 cm³ distilled water to a copper calorimeter.
  3. Insulate calorimeter with draught excluder and lid to minimize heat loss.
  4. Record initial temperature of water, then ignite burner.
  5. Stir water while heating until temperature rises by 20°C, then extinguish burner.
  6. Immediately reweigh burner and fuel after experiment.
  7. Repeat with different alcohols, maintaining consistent variables.
• Less alcohol combusted equates to better fuel economy.
• What is the general formula for Carboxylic acids?


  CnH2n+1COOH.

  
• When alcohols oxidise, they form carboxylic acids.

  
• What is the functional group of carboxylic acid?

  COOH (Carboxyl group).
• A solution of a carboxylic acid behaves similarly to an acid. They are weak acids that partially disassociate and ionise with water to form H+ ions.
• Members of a given homologous series have similar reactions because their molecules contain the same functional group and use this to predict the products of other members of these series.
• Ethanol is produced by fermenting carbohydrates in aqueous solution and using yeast to provide the enzymes.

  
• Explain how to obtain a concentrated solution of ethanol by fractional distillation of the fermentation mixture:

  1. Dilute ethanol solution produced via fermentation.
  2. Ethanol concentration above 20% is achieved through fractional distillation.
  3. Ethanol's lower boiling point than water allows for vaporization during heating.
  4. Liebig condenser cools ethanol vapour, allowing condensation for collection.