Aldehyde & Ketone

1. Aldehyde & Ketone Reactions

2. Formation of an AldehydeOxidation of Primary Alcohols • General equation: • Primary alcohol aldehyde RCH2CH=O EXAMPLE: 1-propanol

3. Formation of a KetoneOxidation of Secondary Alcohols • General equation: • Secondary alcohol ketone O R-C-R EXAMPLE: 2-propanol

4. Review from Chapter 13!!Oxidation of Tertiary Alcohols • General equation: • Tertiary alcohol NO REACTION!!!

5. YOU TRY THESE! • Write an equation showing the oxidation of the following alcohols. Be sure to name the product formed. (a) 1-pentanol (b) 2-butanol

6. Oxidation of Aldehydes • Aldehydes are easily oxidized further to form carboxylic acids. • Oxidation process: Primary alcohol  Aldehyde  Carboxylic acid 1-butanol 2-methyl-1-propanol

7. Reduction Reactions • Both aldehydes and ketones are easily reduced back to the corresponding alcohol. This process is called hydrogenation.

8. Lab Tests for Aldehydes and Ketones Tollen’s Test Tests for ALDEHYDES (not ketones) Silver ion is reduced to silver metal The aldehyde is oxidized to a carboxylic acid anion AKA the Silver Mirror Test

9. Tollen’s Test O O R-CH + Ag(NH3)2 + R-C-O- + Ag0 Aldehyde silver ammonia carboxylic silver complex acid anion metal “Tollen’s Reagent” mirror

10. Write equations for the following reactions 1. ethanal + Tollen’s reagent • 2- pentanone + Tollen’s reagent • propanal + Tollen’s reagent

11. Benedict’s Test • Indicates the presence of an aldehyde • A buffered aqueous solution of copper (II) hydroxide and sodium citrate • Reacts to oxidize aldehydes • Forms a red solid – Cu2O

12. Benedict’s Test • All sugars are aldehydes or ketones • Benedict’s solution can be used to test urine for glucose (an aldehyde), which is common in uncontrolled diabetes • The amount of red precipitate formed is directly proportional to the amount of glucose in the urine.

13. Benedict’s Test • O OH OH H H HC – C - C - C - C - CH2OH + 2Cu+2 H H OH OH (from Benedict’s Solution) O OH OH H H -O - C - C - C - C - C -CH2OH + Cu2O H H OH OHred precipitate

14. Addition Reactions Addition of an Alcohol to an Aldehyde – Acetalformation O H H+ OH H R1-C-H + O-R2 R1-C-OR2 + O-R2 H Aldehyde alcohol Hemiacetal (quite reactive) OR2 H+R1-C-OR2 H Acetal

15. Addition Reactions • -OR group is an alkoxyl group • Hemiacetals are very reactive, so in the presence of acid and excess alcohol, will continue to react to form an acetal

16. Addition Reactions • Addition of an alcohol to a ketone – KETAL formation O H OH H R1-C-R2 + O-R3 H+ R1-C-OR3 + OR3 R2 Ketone alcohol Hemiketal OR3 H+ R1-C-OR3 R2 Ketal

17. Practice Problems • Propanal + Methanol • 3-hexanone + ethanol

18. Keto-EnolTautomers • Many aldehydes & ketones exist in a mixture of two constitutional isomers, informally referred to as tautomers.

19. Practice • Draw the enol form of the aldehydes and ketones listed below. • Ethanal • 2-pentanone • Butanal

20. Aldol Condensation • Reaction in which aldehydes & ketones react to form larger molecules. A new carbon-carbon bond is formed in the process. • Actually occurs between an aldehyde in the keto form and one in the enol form.

21. Example • Write an equation for the aldol condensation of two molecules of butanal.