Further organic chemistry: Carbonyl compounds -4

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  • Created by: Shannon
  • Created on: 07-04-15 09:36
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  • Carbonyl compounds
    • Contain the C=O functional group
    • Aldehydes & Ketones
      • Aldehydes
      • Ketones
      • Properties
        • Boiling points
          • Boiling points increase as the molecule increases in size - intermolecular forces increase
            • London forces as the amount of temporary dipoles increase
            • Aldehyde & Ketones are polar - stronger attraction between permanent dipoles
          • Higher than alkanes - as alkanes not polar
          • Lower than alcohols - as alcohols possess H bonding
        • Solubility
          • Small chain molecules are soluble - as the can H bond with water
          • Decreases as chain length increases
            • Favourable hydrophilic interactions are outweighed by unfavourable hydrophobic interactions
    • Reactions
      • Oxidation with Fehlings/Benedicts
        • Aldehyde = colour change observed, blue solution -> dark red precipitate
        • Ketone = no reaction
      • Oxidation with Tollens
        • Ketone = no reaction
        • Aldehyde = production of a grey precipitate of silver
      • Oxidation with acidified dichromate
        • Ketone = no reaction
        • Aldehyde = colour change from orange solution -> green solution
      • Reduction with LiAlH4 in dry ether
        • Ketone = reduced to secondary alcohol
        • Aldehyde = reduced to primary alcohol
      • With 2,4-DNP
        • Positive result = Orange precipitate will form in the presence of a carbonyl
      • With Iodine and NaOH(aq)
        • Positive result = pale yellow precipitate forms
          • Tests for presence of methyl group next to carbonyl group
      • With HCN & KCN
        • Production of hydroxynitriles
        • KCN needed to provide initial CN- ions
        • Racemic mixture is R1 does not = R2

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