1. Recognise and name aldehydes and ketones.

2. The carbonyl functional group

3. Formation of the C=O group π -bond

4. Structures of benzaldehyde and phenylethanone

5. Describe the reduction of carbonyl compounds to form alcohols. Outline the mechanism for nucleophilic addition reactions of aldehydes and ketones with hydrides.

6. Reduction of an aldehyde produces a primary alcohol Lithium tetrahydridoaluminate LiAlH 4 Source of H - Reacts specifically with polar π bonds

7. The primary alcohol propan-1-ol and the aldehyde propanal

8. Reduction of a ketone produces a secondary alcohol Lithium tetrahydridoaluminate LiAlH 4 Source of H - Reacts specifically with polar π bonds

9. Steps 1.Addition of H- ions to the δ+ C 2.Reagents must be kept dry, carrried out in ether step2 1.Addition of aqueous acid solution, protonates the O-

10. Week 3 Reduction of an aldehyde by nucleophilic addition

11. Both carbonyl compounds and alkenes can be reduced using H 2 & Pt catalyst

12. Describe the use of 2,4-dinitrophenylhydrazine to detect a carbonyl group and to identify a carbonyl compound. Describe the use of Tollens’ reagent to detect the presence of an aldehyde group. Carbonyl compounds react with compounds containing H 2 N- gp. LP on N acts as a nucleophile and forms a bond with δ+ C in C=O. Instead of an H+ adding, it loses a water (elimination) and C=N is formed C=O + H 2 N-X  C=N-X + H 2 O Racemic mixture of products are formed Addition Elimination Reactions

13. © Pearson Education Ltd 2009 This document may have been altered from the original Reaction of propanal with 2,4-dinitrophenylhydrazine Test for carbonyl group

14. 2,4 DNP (Brady's reagent) Product is insoluble, used as test for carbonyl group Simple aldehydes & ketones = yellow ppt Aromatic = orange ppt

15. Identify the product React carbonyl with 2,4 DNP Filter ppt Recrystallise using minimum of hot ethanol Dry & measure melting point Compare to data tables to identify the carbonyl

16. © Pearson Education Ltd 2009 This document may have been altered from the original Describe the oxidation of primary alcohols to form aldehydes and carboxylic acids. Describe the oxidation of secondary alcohols to form ketones. Describe the oxidation of aldehydes to form carboxylic acids.

17. Ethanol oxidised to ethanal, and finally to ethanoic acid

18. Propan-2-ol can be oxidised to propanone

19. © Pearson Education Ltd 2009 This document may have been altered from the original Oxidation of an aldehyde to a carboxylic acid (acid or neutral conditions) Potassium Dichromate (K 2 Cr 2 O 7 )/ H 2 S0 4 KMnO 4 in neutral – brown ppt

20. Oxidation of an aldehyde using Tollens’ reagent (alkaline conditions – NaOH added to silver nitrate) Salt of + H 2 O Distinguish between an aldehyde & Ketone Fehlings reagent (copper(II)sulphate + sodium potassium copper (I) oxide), red ppt when added to an aldehyde

21. Iodoform Reaction Reaction with ethanal and methyl ketones & iodine in alkaline (sodium hydroxide) solutions H atoms of CH 3 C=O are replaced by I Alkali breaks C-C bond to form pale yellow ppt of iodoform CHI 3 is formed Test if substance is ethanol or ethanal

22. Sodium hydroxide solution is added to iodine solution to form iodate ions (IO-) These substitute into the CH3 gp next to C=0. IO- & O are electron withdrawing thus breaking the bond between the 2 C. Result formation of iodoform

23. The reaction I 2 + OH -  IO - + I - CH 3 COR  CI 3 COR  CHI 3 + RCOO - Overall CH 3 COR + 3I 2 + 4NaOH  CHI 3 + RCOONa + 3H 2 0

24. conditions Solutions is warmed with a mixture of iodine and sodium hydroxide Or Potassium iodide in sodium chlorate

25. Summary - Aldehydes + HCN(pH 8) = RCH(OH)CN + [H] = RCH 2 OH + 2,4DNP = yellow orange ppt + K 2 Cr 2 O 7 /H+ = RCOOH + Fehlings/tollens = RCOO- + I 2 /NaOH = CHI 3 + HCOO-

26. Summary Ketones + HCN(pH 8) = RC(OH)R’CN + [H] = RCH(OH)R’ + 2,4DNP = yellow orange ppt + K 2 Cr 2 O 7 /H+ = no reaction + Fehlings/tollens = no reaction + I 2 /NaOH = CHI 3 + R’COO-

27. HCN Adding HCN to carbonyl Need to add KCN as this is easiest to break the bond and form CN- Need to add SULPHURIC acid, help to amplify the polarisation of C=O

28. Oxygen is very electronegative and therefore makes the carbonyl bond very polar Why is KCN added? To increase the number of CN ions present, to speed up the reaction Why is sulphuric acid added? Increases the polarity of the C=O bond

30. Optical isomers – ethanal & HCN Optical isomerism occurs in compounds which have four different groups attached to a single carbon atom. In this case, the product molecule contains a CH 3, a CN, an H and an OH all attached to the central carbon atom.

31. Ethanal is a planar molecule, and attack by a cyanide ion will either be from above the plane of the molecule, or from below. There is an equal chance of either happening.

32. the existing groups get forced down away from the approaching cyanide ion Attack from below forces the existing groups upwards.

33. Now compare that with the molecule formed by attack from above.

34. This argument applies to all aldehydes, and to ketones as long as they are unsymmetrical - with a different alkyl group either side of the carbonyl group. A symmetric ketone like propanone, CH 3 COCH 3, will only produce a single product - not a mixture of isomers. The product doesn't have four different groups around the central carbon atom, and so won't have optical isomers