CHAPTER 8 ALDEHYDES AND KETONES

1. CHAPTER 8 ALDEHYDES AND KETONES

2. Aldehydes and Ketones The carbonyl group Aldehydes have at least one hydrogen attached to the carbonyl group. Ketones have two carbons attached to the carbonyl group.

3. Nomenclature • IUPAC names for aldehydes: • To name an aldehyde, change the suffix -e of the parent alkane to -al. • Because the carbonyl group of an aldehyde can only be at the end of a parent chain and numbering must start with it as carbon-1, there is no need to use a number to locate the aldehyde group. • Name and number substituents as before.

4. Nomenclature 2-ethylbutanal

5. Nomenclature • IUPAC names for ketones: • The parent alkane is the longest chain that contains the carbonyl group. • Indicate the presence of the carbonyl group by changing the -ane of the parent alkane -one. • Number the parent chain from the direction that gives the carbonyl carbon the smaller number. • 2-propanone

6. (d) (c) Draw and name all aldehydes and ketones with the molecular formula C4H8O

7. Physical Properties • A C=O bond is polar, with oxygen bearing a partial negative charge and carbon bearing a partial positive charge • Therefore, aldehydes and ketones are polar molecules

8. Physical Properties • In liquid aldehydes and ketones, there are weak intermolecular attractions are between the partial positive charge on the carbonyl carbon of one molecule and the partial negative charge on the carbonyl oxygen of another molecule. • No hydrogen bonding is possible between aldehyde or ketone molecules. • Aldehydes and ketones have lower boiling points than compounds like alcohols in which there is hydrogen bonding between molecules.

10. Lower molecular weight aldehydes and ketones are infinitely soluble in water. • Aldehydes and ketones become less soluble in water as the hydrocarbon portion of the molecule increases in size. p. 439

11. Reduction The addition of H2 in the presence of catalysts.

12. Oxidation • Aldehydes are oxidized by a variety of oxidizing agents, including potassium dichromate. • Liquid aldehydes are so sensitive to oxidation by O2 of the air that they must be protected from contact with air during storage.

13. Ketones resist oxidation by most oxidizing agents, including potassium dichromate and molecular oxygen.

14. Tollens’ reagent can distinguish between aldehydes and ketones; if done properly, silver deposits on the walls of the container as a silver mirror.

15. Addition of Alcohols • Addition of a molecule of alcohol to the carbonyl group of an aldehyde or ketone forms a hemiacetal (a half-acetal). • The functional group of a hemiacetal is a carbon bonded to one -OH group and one -OR group. • In forming a hemiacetal, H of the alcohol adds to the carbonyl oxygen and OR adds to the carbonyl carbon.

16. Addition of Alcohols • A hemiacetal can react further with an alcohol to form an acetal plus water. • This reaction is acid catalyzed. • The functional group of an acetal is a carbon bonded to two -OR groups.

17. (a) (c) (d) (e) + CH3CH2CH2OH + CH3CH2CH2OH

18. FORMALDEHYDE Simplest Aldehyde IUPAC Name – Methanal Gas at Room Temp. Embalming Fluid

19. automobile windshield washer fluid, gas line antifreeze, copy machine fluid, fuel for small stoves, paint strippers

20. ACETONE Simplest Ketone Airplane glue; nail polish remover; varnishes IUPAC Name – Propanone Dissolves nonpolar substances; soluble In water

21. Hormones Testosterone Anabolic Steroid

22. Testosterone

23. 1988: Johnson stripped of Olympic gold Sprinter Ben Johnson sent home from the Seoul Olympic Games in disgrace. The Canadian was stripped of his 100m gold medal after testing positive for steroids.

24. (Provera®)