Chapter Fifteen Aldehydes And Ketones

Chapter 15 | Slide 2 of 36 In an aldehyde, an H atom is attached to a carbonyl group Ocarbonyl group  CH 3 -C-H In a ketone, two carbon groups are attached to a carbonyl group Ocarbonyl group  CH 3 -C-CH 3 Aldehydes and Ketones

Chapter 15 | Slide 3 of 36

Chapter 15 | Slide 4 of 36 Ketones as Hormones

Chapter 15 | Slide 5 of 36 ←Fig Aldehydes and ketones are related to alcohols in the same manner that alkenes are related to alkanes. Aldehydes and Ketones cont’d

Chapter 15 | Slide 6 of 36 Aldehydes and Ketones →Fig Aldehydes and ketones with the same number of carbon atoms and the same degree of saturation are structural isomers.

Chapter 15 | Slide 7 of 36 Naming Aldehydes Aldehydes are named by replacing the “e” with “____.” The parent chain must contain the –_______ group. The –CHO carbon is always carbon ___. When attached to a ring “carbaldehyde” is used. propaneal hexeneal 2,5-dimethyl 4-ethyl cyclopentane- carbaldehyde 2-

Chapter 15 | Slide 8 of 36 ←Fig Benzaldehyde, the simplest aromatic aldehyde.. Aldehydes and Ketones cont’d

Chapter 15 | Slide 9 of 36 Naming Ketones Ketones are named by replacing the “e” with “_____.” The parent chain must contain the ______. Numbering begins nearer the ______. butaneone heptaneone 3,6-dimethyl 5-ethyl

Chapter 15 | Slide 10 of 36 Name these aldehydes/ketones. 3-penten-2-one 5-methyl-3-cyclohexenone 2-phenylpropanalcyclohexanone

Chapter 15 | Slide 11 of 36 Aldehydes and Ketones cont’d © Harvey Lloyd/Peter Arnold, Inc. ←C.C 15.1 ←Wood Smoke contains formaldehyde and causes eyes to tear. ←Formaldehyde is a lachrymator (eye irritant)

Chapter 15 | Slide 12 of 36 ←Fig Formalin is used to preserve biological specimens. Aldehydes and Ketones cont’d © 2005 Norbert Wu /

Chapter 15 | Slide 13 of 36 © Steven Needham / Envision Aldehydes and Ketones →Fig The delightful odor of melted butter is largely due to butanedione.

Chapter 15 | Slide 14 of 36 Aldehydes and Ketones cont’d

Chapter 15 | Slide 15 of 36 Aldehydes and Ketones Why are some aldehydes and ketones soluble in water?

Chapter 15 | Slide 16 of 36 Physical Properties of Aldehydes and Ketones The polarity of the carbonyl group in aldehydes and ketones, which is responsible for many of their physical properties. –They have boiling points _______ than alcohols but _______ than alkanes. Why? –Nonpolar < Polar (Dipole-dipole) <H-bonds –_____ molecular weight aldehydes and ketones are __________ in water Why not ________ molecular weight aldehydes and ketones? –Most aldehydes and ketones have odors

Chapter 15 | Slide 17 of 36 Aldehydes and Ketones

Chapter 15 | Slide 18 of 36 Oxidation of alcohols. –Primary alcohols yield aldehydes. –Secondary alcohols yield ketones. From primary alcohols From secondary alcohols Synthesis of Aldehydes and Ketones

Chapter 15 | Slide 19 of 36 Oxidation reactions: PCC = Pyridinium chlorochromate

Chapter 15 | Slide 20 of 36 Ketones are unreactive to oxidation because no hydrogens are on the carbon. Oxidation of Aldehydes

Chapter 15 | Slide 21 of 36 Reduction of Aldehydes and Ketones Reduction: Adding hydrogen across the carbonyl –Aldehyde  primary alcohol –Ketone  secondary alcohol + H 2 

Chapter 15 | Slide 22 of 36 Addition Reactions Polar molecules can add to the carbonyl in aldehydes and ketones The negative part of the added molecule adds to the positive carbonyl carbon The positive part of the added molecule adds to the negative carbonyl oxygen  +  -  +  - -C=O + X-Y  -C-O-X Y

Chapter 15 | Slide 23 of 36 Acetal Formation Alcohols add to the carbonyl of aldehydes and ketones The addition of two alcohols forms an acetal. O O-CH 3 CH 3 -C-H + 2 CH 3 -OH  CH 3 -C-H + H 2 O O-CH 3 Hydrolysis of acetals yield the aldehyde or ketone and the alcohols that originally formed the acetal

Chapter 15 | Slide 24 of 36 Hemiacetal Formation The addition of one alcohol to an aldehyde or ketone forms an intermediate called a hemiacetal Usually, hemiacetals are unstable and hard to isolate. O O-CH 3 CH 3 -C-H + 2 CH 3 -OH  CH 3 -C-H + H 2 O O-H

Chapter 15 | Slide 25 of 36 Aldehydes and Ketones CC 15.3 Diabetes, aldehyde oxidation, and glucose testing

Chapter 15 | Slide 26 of 36 Tests for Distinguishing between Aldehydes and Ketones Tollens’ test (AKA Silver Mirror test) –Tollens’ reagent, which contains Ag +, reacts with aldehydes, but not with ketones –The aldehyde is oxidized and Ag + is reduced to Ag, which appears as a silver “mirror” in the test tube (or reaction vessel)

Chapter 15 | Slide 27 of 36 Aldehydes and Ketones cont’d (c) The inside of the beaker becomes coated with metallic silver. (b) The solution darkens as ethanal is oxidized to ethanoic acid. Figs a-c (a) An aqueous solution of ethanal is added to a solution of silver nitrate.

Chapter 15 | Slide 28 of 36 Tests for Distinguishing between Aldehydes and Ketones Benedict’s Test –Benedict’s reagent, which contains Cu +2, reacts with aldehydes that have an adjacent OH group –The aldehyde is oxidized and Cu +2 is reduced Cu 2 O, which appears as a brick red solid in the test tube –Ketones do not react.

Chapter 15 | Slide 29 of 36 Aldehydes and Ketones →Fig Benedict’s solution turns brick red when an aldehyde reacts with it.

Chapter 15 | Slide 30 of 36

Chapter 15 | Slide 31 of 36 Work on the following learning checks as homework.

Chapter 15 | Slide 32 of 36 Classify each as an aldehyde (1), ketone (2) or neither(3). O  A. CH 3 CH 2 CCH 3 B. CH 3 -O-CH 3 CH 3 O  C. CH 3 -C-CH 2 CHD. CH 3 Learning Check

Chapter 15 | Slide 33 of 36 Name the following O  A. CH 3 CH 2 CCH 3 B. CH 3 O  C. CH 3 -C-CH 2 CH CH 3 Learning Check

Chapter 15 | Slide 34 of 36 Draw the structural formulas for each: A. 3-Methylpentanal B. 2,3-Dichloropropanal C. 3-Methyl-2-butanone Learning Check

Chapter 15 | Slide 35 of 36 Learning Check Select the compound that would have the higher boiling point –A. CH 3 -CH 2 -CH 3 or CH 3 -CH 2 -OH –B. CH 3 -CH 2 -OH or CH 3 -O-CH 3 –C.OR

Chapter 15 | Slide 36 of 36 Learning Check Are the following compounds soluble in water? –A. CH 3 -CH 2 -CH 3 –B. CH 3 -CH 2 -OH –C. –D.