Properties of Aldehydes and Ketones Chapter 13 Organic Compounds with oxygen and Sulfur

2 Physical Properties The polar carbonyl group provides dipole-dipole interactions.  +  -  +  - C=O Without an H on the oxygen, aldehydes and ketones cannot form hydrogen bonds.

3 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.

4 Comparison of Boiling Points 58

5 Solubility in Water The electronegative O atom of the carbonyl group of aldehydes and ketones forms hydrogen bonds with water.

6 Learning Check Indicate if each is soluble or insoluble in water. A. CH 3 —CH 2 —CH 3 B. CH 3 —CH 2 —OH O || C. CH 3 —CH 2 —CH 2 —C—H O || D. CH 3 —C—CH 3

7 Solution Indicate if each is soluble or insoluble in water. A. CH 3 —CH 2 —CH 3 insoluble B. CH 3 —CH 2 —OH soluble O || C. CH 3 —CH 2 —CH 2 —C—H soluble O || D. CH 3 —C—CH 3 soluble

8 Tollens’ Test In 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.

9 Benedict’s Test In the Benedict’s test, Benedict’s reagent, which contains Cu 2+, reacts with aldehydes that have an adjacent OH group. An aldehyde is oxidized to a carboxylic acid, while Cu 2+ is reduced to give red Cu 2 O(s).

10 Learning Check Write the structure and name of the oxidized product when each is mixed with Tollens’ reagent. A. butanal B. acetaldehyde C. ethyl methyl ketone

11 Solution A. butanal O || CH 3 —CH 2 —CH 2 —C—OH butanoic acid B. acetaldehyde O || CH 3 —C—OH acetic acid C. ethyl methyl ketoneNone. Ketones are not oxidized by Tollen’s reagent.