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Aldehydes and Ketones

Aldehydes and Ketones. AH Chemistry, Unit 3(b). Functional group. What is the functional group of the aldehydes and ketones?. . . Physical properties. How do the boiling points compare to alkanes ? Why? How do the boiling points compare to alcohols ? Why?. Hydrogen bonding.

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Aldehydes and Ketones

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  1. Aldehydes and Ketones AH Chemistry, Unit 3(b)

  2. Functional group • What is the functional group of the aldehydes and ketones?  

  3. Physical properties • How do the boiling points compare to alkanes? • Why? • How do the boiling points compare to alcohols? • Why?

  4. Hydrogen bonding • Can aldehydes and ketones set up hydrogen bonds with each other? • Can they set them up with water?

  5. Chemical reactions • What are the characteristic reactions of aldehydes and ketones? • Oxidation / Reduction • Nucleophilic addition • Nucleophilic addition-elimination • Which is more susceptible to nucleophilic attack, aldehyde or ketone? • Why?

  6. Oxidation • What reagents can be used to oxidise aldehydes?

  7. Tollens’ reagent

  8. Fehling’s solution

  9. 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 • Must be carried out in anhydrous conditions (in ether)

  10. Nucleophilic addition • With HCN, producing cyanohydrins.... 1 + 2

  11. The cyanohydrins can be hydrolysed to produce hydroxy carboxylic acids

  12. Nucleophilic addition-elimination • With hydrazine, H2N-NH2 • Produces hydrozones • Also referred to as “condensation”.

  13. Specific example • 2,4-dinitrophenylhydrazine • Produces 2,4-dinitrophenylhydrozones

  14. These products are “derivatives”. • They are crystalline solids with characteristic melting points. • The melting point of the derivative can be used to identify the original carbonyl compound.

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