1. General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 14.1 Aldehydes and Ketones Chapter 14 Aldehydes, Ketones, and Chiral Molecules © 2013 Pearson Education, Inc. Lectures

2. © 2013 Pearson Education, Inc. Chapter 14, Section 1 2 Aldehydes and Ketones A carbonyl group,  in an aldehyde, has a carbonyl carbon bonded to one H atom.  in a ketone, has the carbonyl carbon bonded to two carbon groups.

3. © 2013 Pearson Education, Inc. Chapter 14, Section 1 3 Naming Aldehydes An aldehyde  has an IUPAC name in which the -e in the alkane name is changed to -al.  has a common name for the first four aldehydes that use the prefixes: form- (1C), acet- (2C), propion- (3C), and butyr- (4C), followed by -aldehyde.

4. © 2013 Pearson Education, Inc. Chapter 14, Section 1 4 Guide to Naming Aldehydes

5. © 2013 Pearson Education, Inc. Chapter 14, Section 1 5 Aldehydes in Flavorings  Several naturally occurring aldehydes are used as flavorings for foods and fragrances. Benzaldehyde (almonds) Cinnamaldehyde (cinnamon)

6. © 2013 Pearson Education, Inc. Chapter 14, Section 1 6 Naming Ketones Ketones are named  in the IUPAC system by replacing the -e in the alkane name with -one; the carbonyl carbon is indicated by a number.  with a common name by indicating the alkyl groups attached to the carbonyl carbon in alphabetical order followed by ketone.

7. © 2013 Pearson Education, Inc. Chapter 14, Section 1 7 Guide to Naming Ketones

8. © 2013 Pearson Education, Inc. Chapter 14, Section 1 8 Learning Check Give the IUPAC name for the following ketone.

9. © 2013 Pearson Education, Inc. Chapter 14, Section 1 9 Solution Give the IUPAC name for the following ketone. Step 1 Name the longest carbon chain by replacing the -e in the alkane name with -one. cyclopentanone

10. © 2013 Pearson Education, Inc. Chapter 14, Section 1 10 Solution Give the IUPAC name for the following ketone. Step 2 Number the carbon chain from the end nearer the carbonyl group, and indicate its location. 1-cyclopentanone 1 2 3

11. © 2013 Pearson Education, Inc. Chapter 14, Section 1 11 Solution Give the IUPAC name for the following ketone. Step 3 Name and number any substituents on the carbon chain. 3-ethyl-1-cyclopentanone 1 2 3

12. © 2013 Pearson Education, Inc. Chapter 14, Section 1 12 Boiling Points Aldehydes and ketones have  dipole–dipole interactions between polar groups.  higher boiling points than alkanes and ethers of similar mass due to dipole–dipole interactions.  lower boiling points than alcohols of similar mass because they do not form hydrogen bonds.

13. © 2013 Pearson Education, Inc. Chapter 14, Section 1 13 Comparison of Boiling Points

14. © 2013 Pearson Education, Inc. Chapter 14, Section 1 14 Solubility of Aldehydes and Ketones in Water Aldehydes and ketones  with one to four carbons are soluble in water.  with five or more carbons are not very soluble in water.  form hydrogen bonds with water between the carbonyl oxygen and hydrogen atoms of water.

15. © 2013 Pearson Education, Inc. Chapter 14, Section 1 15 Reduction of Aldehydes, Ketones Aldehydes and ketones are reduced by hydrogen (H 2 ) with a catalyst or sodium borohydride (NaBH 4 ), thus  decreasing the number of carbon-oxygen bonds,  reducing aldehydes to primary alcohols, and  reducing ketones to secondary alcohols.

16. © 2013 Pearson Education, Inc. Chapter 14, Section 1 16 Acetals and Hemiacetals Hemiacetals  are carbon atoms that contain a hydroxyl group –OH and an alkoxy group –OR.  are formed when an alcohol adds to an aldehyde or ketone in the presence of an acid catalyst.  react with a second alcohol molecule to produce an acetal, a carbon with two alkoxy groups –OR.

17. © 2013 Pearson Education, Inc. Chapter 14, Section 1 17 Acetals from Aldehydes Alcohol adds to the aldehyde carbonyl producing a hemiacetal. When a second alcohol adds, it forms an acetal.

18. © 2013 Pearson Education, Inc. Chapter 14, Section 1 18 Acetals from Ketones Ketones  are less reactive than aldehydes because the carbonyl carbon is more positive in aldehydes.  react with one alcohol molecule to form a hemiacetal, and react with a second alcohol molecule to form an acetal.

19. © 2013 Pearson Education, Inc. Chapter 14, Section 1 19 Stereoisomers Structural Isomers have the same formula but different bonding arrangements. Stereoisomers have atoms that are bonded in the same sequence, but differ in the way they are arranged in space. Stereoisomers are molecules that are nonsuperimposable mirror images.

20. © 2013 Pearson Education, Inc. Chapter 14, Section 1 20 Chirality  Molecules are chiral when their mirror images cannot be completely matched. They are said to be nonsuperimposable.  Your hands are chiral. Try to superimpose your thumbs, palms, back of hands, and little fingers.  When the mirror image of an object is identical and can be superimposed on the original, it is achiral.

21. © 2013 Pearson Education, Inc. Chapter 14, Section 1 21 Hands Are Like Chiral Objects

22. © 2013 Pearson Education, Inc. Chapter 14, Section 1 22 Chiral or Achiral

23. © 2013 Pearson Education, Inc. Chapter 14, Section 1 23 Chiral Carbon Atoms Carbon atoms are chiral if  they have 4 different atoms or groups.  they have mirror images like your hands. When stereoisomers cannot be superimposed, they are called enantiomers.

24. © 2013 Pearson Education, Inc. Chapter 14, Section 1 24 Mirror Images The mirror images of bromochloroiodomethane can align the H and I atoms, which places the Cl and Br atoms on opposite sides. (a) The enantiomers of a chiral molecule are mirror images. (b) The enantiomers of a chiral molecule cannot be superimposed on. each other.

25. © 2013 Pearson Education, Inc. Chapter 14, Section 1 25 Achiral Structures Are Superimposable When the mirror image of an achiral structure is rotated,  the structure is aligned with its initial structure.  its mirror image is superimposable.

26. © 2013 Pearson Education, Inc. Chapter 14, Section 1 26 Biological Effects of Stereoisomers Molecules in nature also have mirror images, and often one stereoisomer has a different biological effect than the other one.

27. © 2013 Pearson Education, Inc. Chapter 14, Section 1 27 Learning Check Identify each as a chiral or achiral compound. A.B.C.

28. © 2013 Pearson Education, Inc. Chapter 14, Section 1 28 Solution Identify each as a chiral or achiral compound. A.B.C. chiral antichiral

29. © 2013 Pearson Education, Inc. Chapter 14, Section 1 29 Fischer Projections A Fischer projection  is a two-dimensional representation of a molecule.  places the most oxidized group at the top.  uses vertical lines for bonds that go back.  uses horizontal lines for bonds that go forward.

30. © 2013 Pearson Education, Inc. Chapter 14, Section 1 30 Drawing Fischer Projections For compounds with two or more chiral carbons, the designation as a D or L isomer is determined by the position of the –OH group attached to the chiral carbon farthest from the carbonyl group.

31. © 2013 Pearson Education, Inc. Chapter 14, Section 1 31 Learning Check Indicate whether each of the following pairs of Fischer projections can or cannot be superimposed.

32. © 2013 Pearson Education, Inc. Chapter 14, Section 1 32 Solution Indicate whether each of the following pairs of Fischer projections can or cannot be superimposed: cannot be superimposed can be superimposed

33. © 2013 Pearson Education, Inc. Chapter 14, Section 1 33 Learning Check Identify the following as a D or L isomer.

34. © 2013 Pearson Education, Inc. Chapter 14, Section 1 34 Solution Identify the following as a D or L isomer. The –OH group is on the right, it is a D isomer.