carbonyls

Question 1

What are the 2 nucleophilic addition reactions?

Answer 1

• With NaBH4 - reduction reaction
• with HCN adds extra carbon to chain

Question 2

What are aldehydes and ketones reduced to?

Answer 2

• Aldehydes can be reduced to primary alcohols.
• Ketones can be reduced to secondary alcohols (require powerful reducing agent - NaBH4)

Question 3

Nucleophilic addition with NaBH4

Answer 3

CH3COCH3 + 2[H] -> CH3CH(OH)CH3
- NaBH4 (aq) -> source of :H- (hydroxide ion)

Question 4

CH3CHO + 2[H] ->
CH3COCH3 + 2[H] ->
CH3CH2CHO + 2[H] ->

Answer 4

CH3CH2OH aldehyde -> primary alcohol
CH3CH(CH3)OH ketone -> secondary alcohol
CH3OH2CH2OH aldehyde -> primary alcohol

Question 5

Nucleophilic addition with HCN

Answer 5

• Aldehyde/ketones + HCN -> hydroxynitrile (containing both OH and CN functional group)
• HCN -> provides the :CN-
• Extends chain by 1 carbon chain
• CH3CHO + HCN -> CH3CH(OH)CN

Question 6

Test for carbonyls

Answer 6

+ test : yellow or orange precipitate -> called the 2,4,DNPH derivative -> used to name unknown carbonyl as it has a unique melting point.

Question 7

Differentiating aldehydes from ketones

Answer 7

• Ammoniacal silver nitrate / Tollens reagent.
• Made by adding NaOH (aq) to AgNO3 and dissolving the precipitate with NH3
• Produces a silver mirror when warmed with aldehyde only.
• The AgI reduced to Ag -> the aldehyde has therefore been reduced.