Oxidising Alcohols

• How are alcohols classified?

  Based on the number of carbon atoms
• What defines a primary alcohol?

  It has -OH on a carbon bonded to one carbon
• What characterizes a secondary alcohol?

  It has -OH on a carbon bonded to two carbons
• Provide an example of a secondary alcohol.

  Propan-2-ol (CH₃CH(OH)CH₃)
• What is the oxidation product of ethanol?

  Ethanal (CH₃CHO)
• What is the oxidation product of propan-2-ol?

  Propanone (CH₃COCH₃)
• Why can't tertiary alcohols be oxidised?

  They lack a hydrogen atom on the carbon with -OH
• What is the only way to oxidise tertiary alcohols?

  Through combustion
• What happens to the color of the solution when primary and secondary alcohols react with K₂Cr₂O₇?

  The solution changes from orange to green
• What is the notation used to denote an oxidising agent?

  [O]
• How can you produce an aldehyde from a primary alcohol?

  Gently heat with acidified K₂Cr₂O₇
• Why is it challenging to stop the oxidation of primary alcohols at the aldehyde stage?

  They tend to oxidise further to carboxylic acids
• What apparatus is used to collect the distillate during aldehyde formation?

  A distillation apparatus
• Why does the aldehyde vaporise during the reaction?

  It has a lower boiling point than the alcohol
• What is the reaction for oxidising a primary alcohol to a carboxylic acid?

  R-CH₂OH + 2[O] → R-COOH + H₂O
• What is the purpose of the Liebig condenser in the reflux process?

  To cool and condense vapours back into liquid
• Why are ketones typically stable?

  They do not oxidise further under normal conditions
• Why are aldehydes easily oxidised?

  They have a hydrogen atom on the carbonyl carbon
• What happens in Fehling’s test with aldehydes?

  Aldehydes reduce Cu²⁺ ions to form red precipitate
• What is the result of Benedict’s test for aldehydes?

  Aldehydes reduce blue Cu²⁺ ions to red precipitate
• What is the procedure for Tollens’ test?

  Mix sample with Tollens’ reagent and heat gently
• What is the result of Tollens’ test for aldehydes?

  A shiny silver mirror forms on the test tube
• What is an elimination reaction involving alcohols?

  Removal of water to form an alkene
• What is another name for dehydration reactions?

  Elimination reactions
• How can alkenes be produced sustainably?

  By using alcohols from renewable sources
• What is the reaction for dehydrating ethanol?

  C₂H₅OH → CH₂=CH₂ + H₂O
• What is the first step in the dehydration of ethanol?

  Protonation of the ethanol molecule by acid
• What is the final step in the dehydration of ethanol?

  A proton is eliminated from the carbocation
• What occurs after the formation of a carbocation in ethanol dehydration?

  A water molecule is lost
• What is the first step in distilling cyclohexene?

  Weigh the cyclohexanol
• What is added to cyclohexanol before distillation?

  Phosphoric acid
• What is the purpose of anti-bumping granules in distillation?

  To ensure smoother boiling
• What is the boiling point of cyclohexene?

  Around 83°C
• How do you separate distilled liquid into layers?

  Use a separating funnel with sodium chloride
• What is added to crude cyclohexene to remove water?

  Anhydrous calcium chloride
• How do you confirm the presence of cyclohexene?

  Use bromine water to test
• What does a separating funnel do in distillation?

  Separates layers based on density differences