1 Chapter 14 Aldehydes, Ketones, and Chiral Molecules 14.1 Aldehydes and Ketones Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Aldehydes in Flavorings  Several naturally occurring aldehydes are used as flavorings for foods and fragrances. Benzaldehyde (almonds) Cinnamaldehyde (cinnamon) Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

3 Ketones in Common Use Nail polish remover, Solvent Propanone, Dimethylketone, Acetone Butter flavoring Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

4 Carbonyl Group in Aldehydes and Ketones A carbonyl group  In an aldehyde is attached to at least one H atom.  In a ketone is attached to two carbon groups. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

5 Naming Aldehydes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

6 Naming Ketones O O ║ ║ CH 3 − C − CH 3 CH 3 − C − CH 2 − CH 3 propanone 2-butanone (dimethyl ketone) (ethyl methyl ketone)

7 Boiling Points Aldehydes and ketones have  Polar carbonyl groups (C=O).  +  - C=O  Attractions between polar groups.  +  -  +  - C=O  Higher boiling points than alkanes and ethers of similar mass.  Lower boiling points than alcohols of similar mass.

8 Comparison of Boiling Points 58 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

9 Solubility in Water Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

10 Oxidation  Aldehydes are easily oxidized to carboxylic acids. O O || [O] || CH 3 —C—H CH 3 —C—OH AcetaldehydeAcetic acid

11 Tollens’ Test  Tollens’ reagent, which contains Ag +, oxidizes aldehydes, but not ketones.  Ag + is reduced to metallic Ag, which appears as a “mirror” in the test tube. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

12 Benedict’s Test In the Benedict’s Test,  Cu 2+ reacts with aldehydes that have an adjacent OH group.  Aldehydes are oxidized to carboxylic acids.  Cu 2+ is reduced to give Cu 2 O(s). Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

13 Reduction of Aldehydes and Ketones

14 Addition Reactions |  +  -  +  - | —C=O + X—Y —C—O—X | Y

15 Addition of Water

16 Hemiacetal Formation Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

17 Acetal Formation Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

18 Cyclic Hemiacetals A stable cyclic hemiacetal forms when the C=O group and the —OH are both part of a five- or six-atom carbon compound. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

19 Mirror Images The mirror images of  Chiral compounds cannot be superimposed.  Two compounds of bromochloroiodomethane can align the H and I atoms, which places the Cl and Br atoms on opposite sides. Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

20 Achiral Structures are Superimposable  When the mirror image of an achiral structure is rotated, the structure can be aligned with the initial structure. Thus this mirror image is superimposable. Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

21 Some Everyday Chiral and Achiral Objects

22 Fischer Projections A Fischer projection  Is a 2-dimensional representation of a 3-dimensional molecule.  Places the most oxidized group at the top.  Uses vertical lines in place of dashes for bonds that go back.  Uses horizontal lines in place of wedges for bonds that come forward.

23 Drawing Fischer Projections Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

24 D and L Notations  By convention, the letter L is assigned to the structure with the —OH on the left.  The letter D is assigned to the structure with the —OH on the right. Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings