1. 17.5 Reactions of Aldehydes and Ketones: A Review and a Preview Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Already covered in earlier chapters: Reduction of C=O to CH 2 Clemmensen reduction Wolff-Kishner reduction Reduction of C=O to CHOH Addition of Grignard and organolithium reagents Table 17.2 Reactions of Aldehydes and Ketones

3. 17.6 Principles of Nucleophilic Addition: Hydration of Aldehydes and Ketones

4. H2OH2O Hydration of Aldehydes and Ketones C O HO C O H

5. compared to H electronic: alkyl groups stabilize reactants steric: alkyl groups crowd product OH R R' + H2OH2O C C R O Substituent Effects on Hydration Equilibria

6. C=OhydrateK%Relative rate CH 2 =OCH 2 (OH) 2 2300>99.92200 CH 3 CH=OCH 3 CH(OH) 2 1.0501.0 (CH 3 ) 3 CCH=O(CH 3 ) 3 CCH(OH) 2 0.2170.09 (CH 3 ) 2 C=O(CH 3 ) 2 C(OH) 2 0.00140.140.0018 Table 17.3 Equilibrium Constants and Relative Rates of Hydration

7. When carbonyl group is destabilized alkyl groups stabilize C=O electron-withdrawing groups destabilize C=O When Does Equilibrium Favor Hydrate?

8. OH R R + H2OH2O C C R R O Substituent Effects on Hydration Equilibria R = CH 3 : K = 0.0014 R = CF 3 : K = 22,000

9. Mechanism of Hydration (base) C O O H – Step 1: + HO C O –

10. Mechanism of Hydration (base) Step 2: HO C O – + O H – HO C OHOH O H H

11. Mechanism of Hydration (acid) C O Step 1: + + C OHOH + H O H H OH H +

12. Mechanism of Hydration (acid) Step 2: C OH + + H O H C OH H O H +

13. Mechanism of Hydration (acid) Step 3: + H O H C OHOH H O H O H C OHOH + H H O H +

14. 17.7 Cyanohydrin Formation

15. + Cyanohydrin Formation CO HCN H C O NC

16. Cyanohydrin Formation CO C – N

17. Cyanohydrin Formation – O NC C H H H + O H H O O NC C H

18. 2,4-Dichlorobenzaldehyde cyanohydrin (100%) Example Cl CH O Cl CHCN OH NaCN, water then H 2 SO 4

19. Example CH 3 CCH 3 O NaCN, water then H 2 SO 4 CH 3 CCH 3 OH CN (77-78%) Acetone cyanohydrin is used in the synthesis of methacrylonitrile (see problem 17.8).