Aldehydes and ketones

• What is a carbonyl group?

  C=O bond
• What is used to show the reducing agent in equations?

  2 [H]
• What is the reducing agent for carbonyl reactions?

  NaBH4 = sodium borohydride
• What is the reaction mechanism name for carbonyl reduction?

  Nucleophilic addition
• What is the nucleophile used?

  H-
• What are the conditions for nucleophilic addition?

  Aqueous solution
• What is added during the intermediate step?

  A water molecule
• What is an aldehyde reduced to?

  A primary alcohol
• What is a ketone reduced to?

  A secondary alcohol
• What is the complex ion for Tollen's reagent?

  [Ag(NH3)2]+
• Describe reduction of an aldehyde

  The lone pair on a hydride ion is attracted to the C that is part of the carbonyl group

  Then, a curly arrow from the double bond to the O shows the double bond being broken

  O gains a lone pair and becomes a negative ion and is attracted to the delta positive hydrogen which is part of a water molecule, due to the aqueous conditions
• Describe the reduction of a ketone

  The lone pair on a hydride ion is attracted to the C that is part of the carbonyl group

  Then, a curly arrow from the double bond to the O shows the double bond being broken

  O gains a lone pair and becomes a negative ion and is attracted to the delta positive hydrogen which is part of a water molecule, due to the aqueous conditions

  An asymmetric carbon is formed (chiral centre)
• Explain why the product of reduction of a ketone is not optically active

  -The carbonyl group is trigonal planar

  -Therefore, the H- ion can attack above or below with equal chance

  -Therefore, a racemic mixture is formed

  -Therefore, plane polarised light is rotated equally in opposite directions
• What are the conditions and reagents for nucleophilic addition when making hydroxy nitriles?

  KCN followed by HCl (supplier of H+)
• Describe the reaction of an aldehyde to form a hydroxy nitrile

  -C from the CN is negative and has a lone pair due to only three bonds

  -Curly arrow from lone pair on C to the carbon part of the carbonyl group

  -Curly arrow from the double bond to the oxygen

  -HCl supplies H+ as it is an acid so the curly arrow goes from the negative oxygen with a lone pair to the H+

  -Forming a 2-hydroxynitrile
• Describe the reaction of a ketone to form a hydroxy nitrile

  -C from the CN is negative and has a lone pair due to only three bonds

  -Curly arrow from lone pair on C to the carbon part of the carbonyl group

  -Curly arrow from the double bond to the oxygen

  -HCl supplies H+ as it is an acid so the curly arrow goes from the negative oxygen with a lone pair to the H+

  -Forming a 2-hydroxynitrile