Aldehydes and Ketones

• What are carbonyl compounds?

  Compounds with a C=O bond
• How can carbonyls be classified?

  As aldehydes or ketones
• What defines an aldehyde in terms of structure?

  C=O on the end of the chain
• What suffix do aldehydes end with?


  • al
• What is the formula for ethanal?

  CH3CHO
• What defines a ketone in terms of structure?

  C=O in the middle of the chain
• What suffix do ketones end with?

  • one
• What is the formula for propanone?

  CH3COCH3
• Why are smaller carbonyls soluble in water?

  They can form hydrogen bonds with water
• What type of intermolecular forces do pure carbonyls exhibit?

  Permanent dipole forces
• How does the strength of the C=O bond compare to C=C bonds?

  C=O is stronger and less reactive
• Why is the C=O bond polarized?

  O is more electronegative than carbon
• What type of species are attracted to the positive carbon atom in carbonyls?

  Nucleophiles
• What happens to primary alcohols during oxidation?

  They form aldehydes
• What happens to secondary alcohols during oxidation?

  They form ketones
• What happens to tertiary alcohols during oxidation?

  They do not oxidize
• What is the oxidizing agent that causes alcohols and aldehydes to oxidize?

  Potassium dichromate (K2Cr2O7)
• What is a key point regarding the oxidation of aldehydes and ketones?

  Aldehydes can oxidize, ketones cannot
• What is the reaction of an aldehyde when oxidized?

  Aldehyde forms a carboxylic acid
• What reagents are used for the oxidation of aldehydes?

  Potassium dichromate and dilute sulfuric acid
• What conditions are required for the oxidation of aldehydes?

  Heat under reflux
• What is the full equation for the oxidation of ethanal?

  3CH3CHO + Cr2O7^2- + 8H+ → 3CH3CO2H + 4H2O + 2Cr3+
• What is observed during the oxidation of aldehydes with potassium dichromate?

  Orange dichromate reduces to green Cr3+
• What reagents can oxidize aldehydes besides potassium dichromate?

  Fehling’s solution and Tollen’s reagent
• What is the observation when aldehydes are oxidized using Fehling’s solution?

  Blue Cu2+ ions change to red precipitate
• What happens to ketones when treated with Fehling’s solution?

  They do not react
• What is the reaction of aldehydes with Tollen’s reagent?

  Aldehydes are oxidized to carboxylic acids
• What is observed when aldehydes react with Tollen’s reagent?

  A silver mirror forms in the test tube
• What is the reaction of carbonyls with hydrogen cyanide?

  Carbonyls form hydroxynitriles
• What reagents are used to add hydrogen cyanide to carbonyls?

  Potassium cyanide and dilute sulfuric acid
• What conditions are required for the reaction of carbonyls with hydrogen cyanide?

  Room temperature and pressure
• What is the mechanism of the reaction between carbonyls and hydrogen cyanide?

  Nucleophilic addition
• How is the CN group named in hydroxynitriles?

  It becomes part of the main chain
• What is the result of using HCN in the reaction with carbonyls?

  It is toxic and difficult to contain
• Why are KCN or NaCN preferred over HCN?

  They ionize completely, providing more CN- ions
• What type of mixture forms when HCN is used in the reaction with carbonyls?

  A racemic mixture of enantiomers
• What is the result of nucleophilic addition of HCN to unsymmetrical carbonyls?

  A racemate forms due to equal attack