Module 6.1.2- Carbonyl compounds

• Carbonyl group


  C=O

  
• Naming carbonyl compounds- aldehyde


  -al for aldehyde the position of the aldehyde is never recorded in the name because it is always on carbon-1. in a ketone, the carbonyl group can be at any position on the chain except at the end, so it's important to include its position in the name.
• Naming carbonyl compounds- ketone


  -one for ketonein a ketone, the carbonyl group can be at any position on the chain except at the end, so it's important to include its position in the name.
• Name this compound

  pentan-2-one

  
• Oxidation of Aldehydes

  Form carboxylic acids

  using K2Cr2O7/H2SO4
• Oxidation of Ketones

  They can't.
• Nucleophile


  An electron pair donor
• Nucleophilic addition


  Nucleophile is attracted to and attacks the slightly positive carbon atom

  
• Name of mechanism of C=C with electrophiles

  electrophilic addition(do not get mixed up!!)
• reducing agent [H]


  NaBH4
• Reducing an aldehyde


  Forms a primary alcohol. Uses NaBH4 in an aqueous solution (H2O). Warmed.

  
• Reducing a ketone


  Forms a secondary alcohol. Uses NaBH4 in an aqueous solution (H2O). Warmed.

  
• Reaction of carbonyl compounds with HCN


  HCN adds across the C=O double bond in aldehydes and ketones Poisonous so NaCN/H2SO4 used to provide hydrogen cyanide Very useful as provides a means of increasing the length of the carbon chain Forms a hydroxynitrile (OH and CN group)Addition reaction

  
• Hydroxynitrile


  A molecule with a CN and OH group.

  
• Reaction of carbonyl compounds with HCN Mechanism


  1) lone pair from CN- molecule is donated to the C in the C=O forming a dative covalent bond

  2) pi bond in C=O breaks by heterolytic fission forming a negatively charged intermediate

  3) intermediate is protonated by donating lone pair to H+ ion (or water)

  
• Reaction of carbonyl compounds with NaBH4 Mechanism


  1) lone pair from the hydride ion H- is donated to the C in the C=O double bond forming a dative bond

  2) pi bond in C=O breaks by heterolytic fission forming a negatively charged intermediate

  3) oxygen atom donates a lone pair of electrons to a H+ atom in a water molecule. Alcohol is then formed.

  
• Test the presence of carbonyl functional group


  2,4-DNP
• After adding 2,4-DNP what do you observe when there's a carbonyl function group

  Yellow or orange precipitate
• Test for aldehydes


  Tollens reagent: silver mirror(silver nitrate in aqueous ammonia)
• What happens when tollens reagent is added to aldehyde


  Ag+ ions act as an oxidising agent in the presence of ammonia. Silver ions are also reduced to silver

  Aldehyde is oxidised to carboxylic acid

  Redox reaction