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Aldehydes and Ketones. AH Chemistry Unit 3(b). Functional Group. What is the functional group of the aldehydes and ketones? What type of bonds link the C and O atoms?. Physical Properties. How do the boiling points compare to alkanes ? Why?
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Aldehydes and Ketones AH Chemistry Unit 3(b)
Functional Group • What is the functional group of the aldehydes and ketones? • What type of bonds link the C and O atoms?
Physical Properties • How do the boiling points compare to alkanes? • Why? • How do the boiling points compare to alcohols? • Why?
Can aldehydes and ketones set up hydrogen bonds with each other? • Can they set them up with water?
Chemical reactions • What are the characteristic reactions of aledehydes and ketones? • Reduction • Nucleophilic addition • Nucleophilic addition-elimination • Which is more susceptible to nucleophilic attack, aldehyde or ketone? • Why?
Oxidation • What reagents can be used to oxidise aldehydes?
Reduction • Aldehydes and ketones can be reduced to produce alcohols. • The reducing agent of choice is LiAlH4 - lithium aluminium hydride • Able to transfer a hydride ion to the partially positive carbon atom of the carbonyl group • Musty be carried out in anhydrous conditions (in ether)
Nucleophilic addition • With HCN, producing cyanohydrins....
The cyanohydrins can be hydrolysed to produce hydroxy carboxylic acids
Nucleophilic addition-elimination - With hydrazine, H2N-NH2 - Produces hydrozones
Nucleophilic addition Elimination CONDENSATION
- With 2,4-dinitrophenylhydrazine - Produces 2,4-dinitrophenylhydrozones These products are “derivatives”. They are crystalline solids with characteristic melting points. The melting point of the derivative can be used to identify the orignial carbonyl compound.