Aldehydes, Ketones and Chiral Molecules - Principles of Chemistry II | CHEM 1212, Study notes of Chemistry

Download Aldehydes, Ketones and Chiral Molecules - Principles of Chemistry II | CHEM 1212 and more Study notes Chemistry in PDF only on Docsity! 174 14 Aldehydes, Ketones, and Chiral Molecules Study Goals ● Name and write the condensed structural formulas for aldehydes and ketones. ● Describe some important aldehydes and ketones. ● Identify the chiral carbon atoms in organic molecules. ● Write equations for the oxidation of aldehydes and for the reduction of aldehydes and ketones. ● Draw the structural formulas of hemiacetals and acetals produced from the addition of alcohols to aldehydes and ketones. Chapter Outline 14.1 Aldehydes and Ketones Environmental Note: Vanilla Health Note: Some Important Aldehydes and Ketones 14.2 Physical Properties 14.3 Oxidation and Reduction 14.4 Addition Reactions 14.5 Chiral Molecules Health Note: Enantiomers in Biological Systems Chapter Summary and Demonstrations 1. Aldehydes and Ketones The study of organic functional groups continues with the carbonyl group of aldehydes and ketones. The properties of ketones and aldehydes are discussed, including hydrogen bonding, boiling points, and solubility in water. IUPAC names and common names, if prevalent, are given for ketones and aldehydes. Demonstration: Look for names of aldehydes and/or ketones on the labels of products such as mouthwash, antifreeze, rubbing alcohol, food flavorings, cosmetics, and hair spray. 2. Chiral Molecules Chiral molecules have one or more chiral carbons, which are bonded to four different atoms of groups of atoms. Chiral molecules known as stereoisomers have the same atoms bonded but with different arrangements in space. Stereoisomers known as enantiomers have mirror images that cannot be superimposed. Demonstration: Models of Chiral Molecules I start the discussion of chirality by having students compare their hands. Looking at their palms, we see that our thumbs go in opposite directions. We can match the direction of the thumbs only if we have one palm up and one palm down. If the hands face each other, they are mirror images. I use a mirror in class to provide the image of the other hand. Model kits are very useful in building simple chiral molecules. I give students a formula such as CFClBrI and ask them to make the model. I try to find the mirror image among the models and compare the two. Or I ask students to now make a mirror image of the first model. Eventually, this hands-on, visual approach 46475_14_p174-186 4/12/06 8:31 AM Page 174 175 Aldehydes, Ketones, and Chiral Molecules helps students to understand the three-dimensional relationship between mirror images that is difficult to show in two dimensions. I make some larger models with an 9OH group, aldehyde group, 9CH3 group, and 9CH2OH group. We make the mirror image as well. Then I present some ways to draw the structure using Fischer projections. Laboratory Suggestions LABORATORY MANUAL Lab 25 Aldehydes and Ketones Laboratory tests are used to identify the functional groups of aldehydes and ketones and chemical and physical properties. Aldehydes are oxidized, and the structural formulas of the oxidation products are written. A. Structures of Some Aldehydes and Ketones B. Properties of Aldehydes and Ketones C. Iodoform Test for Methyl Ketones D. Oxidation of Aldehydes and Ketones E. Identification of an Unknown Laboratory Skills to Demonstrate Proper technique for noting the odor of a substance in a test tube Identification of a change in the orange color of chromic acid to green as an indication of the occurrence of an oxidation reaction Identification of changes in the iodoform test Identification of a change from the blue color of Benedict’s reagent to various shades of green to red-orange as a positive test for the oxidation of aldehydes to carboxylic acids ESSENTIAL LABORATORY MANUAL Lab 17 Alcohols, Aldehydes, and Ketones Laboratory tests are used to identify the functional groups of aldehydes and ketones and chemical and physical properties. Aldehydes are oxidized, and the structural formulas of the oxidation products are written. A. Properties of Aldehydes and Ketones B. Iodoform Test for Methyl Ketones C. Oxidation of Aldehydes and Ketones Laboratory Skills to Demonstrate Proper technique for noting the odor of a substance in a test tube. Identification of a change in the orange color of chromic acid to green as an indication of the occurrence of an oxidation reaction. Identification of changes in the iodoform test. Answers and Solutions to Selected Text Problems 14.1 a. ketone b. aldehyde c. ketone d. aldehyde 14.2 a. aldehyde b. aldehyde c. ketone d. ketone 46475_14_p174-186 4/12/06 8:31 AM Page 175 14.21 a. A primary alcohol will be oxidized to an aldehyde and then to a carboxylic acid. then b. A secondary alcohol will be oxidized to a ketone. c. A secondary alcohol will be oxidized to a ketone. d. A secondary alcohol will be oxidized to a ketone. e. A primary alcohol will be oxidized to an aldehyde and then to a carboxylic acid. then 14.22 a. b. c. none d. e. 14.23 In reduction, an aldehyde will give a primary alcohol and a ketone will give a secondary alcohol. a. Butyraldehyde is the four-carbon aldehyde; it will be reduced to a four-carbon, primary alcohol. CH3¬CH2¬CH2¬CH2¬OH b. Acetone is a three-carbon ketone; it will be reduced to a three carbon secondary alcohol. c. 3-bromohexanal is a six-carbon aldehyde with bromine attached to carbon 3. It reduces to a six- carbon primary alcohol with bromine on carbon 3. d. 2-methyl-3-pentanone is a five-carbon ketone with a methyl group attached to carbon 2. It will be reduced to a five-carbon secondary alcohol with a methyl attached to carbon 2. OH CH39CH9CH9CH29CH3 CH3 Br CH39CH29CH29CH9CH29CH29OH OH CH39CH9CH3 O CH39C9C9CH29CH3 O O CH39CH9CH29C9CH3 OCH3 C9H O CH3 CH39CH9CH29C9OH OCH3 CH39CH9CH29C9H O CH3 CH39C9CH29CH9CH3 O O CH39CH29C9CH3 O CH39CH29CH29CH29C9OH O CH39CH29CH29CH29C9H O 178 Chapter 14 46475_14_p174-186 4/12/06 8:31 AM Page 178 14.24 a. b. CH39OH c. d. 14.25 a. b. 14.26 a. b. 14.27 a. hemiacetal (ethanol and formaldehyde) b. hemiacetal c. acetal d. hemiacetal e. acetal 14.28 a. neither b. neither c. hemiacetal d. acetal e. neither 14.29 A hemiacetal forms when an alcohol is added to the carbonyl of an aldehyde or ketone. a. b. c. d. 14.30 a. b. c. d. 14.31 An acetal forms when a second molecule of alcohol reacts with a hemiacetal. a. b. CH39C9CH3 O9CH3 O9CH3 CH39C9H O9CH3 O9CH3 H9C9H O9CH29CH3 OH O9CH29CH3HO CH39CH29C9CH3 O9CH29CH3 OH CH39CH29C9H O9CH29CH3 OH CH39CH29CH29C9H O9CH3 OH OCH3HO CH39C9CH3 O9CH3 OH CH39C9H O9CH3 OH CH29C9CH3 OH OH OH OH CH39CH29C9H OH OH H9C9H OH OH CH39C9H CH39CH9CH29CH29CH3 OH OH Cl CH39CH29CH9CH29CH29CH3 OH 179 Aldehydes, Ketones, and Chiral Molecules 46475_14_p174-186 4/12/06 8:31 AM Page 179 c. d. 14.32 a. b. c. d. 14.33 a. achiral b. chiral c. chiral d. achiral 14.34 a. Chiral; carbon 2 is bonded to four different atoms or groups. b. Achiral; there are no carbon atoms attached to four different groups. c. Chiral; there are carbon atoms that are attached to four different groups. d. Chiral; carbon 2 is bonded to a chlorine atom, hydrogen atom, methyl group, and a ¬CH2¬Br group 14.35 a. b. 14.36 a. b. 14.37 a. b. c. HO99H CHO CH2CH3 Cl99Br OH CH3 HO99Br H CH3 HO HO OH CH9CH29NH2CH3 9CH29CH9NH2 CH3 O chiral carbon H2N9CH9C9OH CH39C"CH9CH29CH29CH9CH29CH29OH CH3 chiral carbonCH3 Ochiral carbon CH39CH9C9H Br chiral carbon CH39CH9CH29CH3 Br H9C9H O9CH29CH3 O9CH29CH3 O9CH29CH3CH39CH29O CH39CH29C9CH3 O9CH29CH3 O9CH29CH3 CH39CH29C9H O9CH29CH3 O9CH29CH3 CH39CH29CH29C9H O9CH3 O9CH3 OCH3CH3O 180 Chapter 14 46475_14_p174-186 4/27/06 7:27 AM Page 180 14.53 a. CH3¬CH2¬OH; polar ¬OH group can hydrogen bond b. polar carbonyl group c. CH3¬CH2¬CH2¬OH; polar ¬OH group can hydrogen bond 14.54 a. greater molar mass of the two carbonyl compounds b. dipole-dipole interactions increased boiling point compared with an alkane. c. the ¬OH can form hydrogen bonds. 14.55 A chiral carbon is bonded to four different groups. a. b. none c. none d. e. f. none 14.56 a. none b. c. none d. none e. f. none 14.57 Enantiomers are mirror images. a. identical b. enantiomers c. enantiomers (turn 180°) d. enantiomers 14.58 a. enantiomers b. identical c. identical d. enantiomers 14.59 Primary alcohols oxidize to aldehydes and then to carboxylic acids. Secondary alcohols oxidize to ketones. a. further oxidation CH39CH29C9H O CH39CH29C9OH O CH39C9CH29CH3 Br OH O CH39CH9C9CH3 OH CH39CH29CH9CH29CH29CH3 BrO CH39CH9C9H NH2 H9C9C9O9H Cl Cl Cl H CH39CH9CH3; OH CH39C9CH3; O CH39CH29CH29CH29C9H; O CH39CH29C9H; O 183 Aldehydes, Ketones, and Chiral Molecules 46475_14_p174-186 4/12/06 8:31 AM Page 183 b. c. d. 14.60 a. b. c. d. 14.61 a. b. c. 14.62 a. CH3¬CH2¬OH b. c. CH3¬OH 14.63 a. b. O Ni CH39CH29CH29C9H
H2 CH39CH29CH29CH29OH H
, heat propene propanone OOH H
[O] CH39CH"CH2
H2O CH39CH9CH3 CH39C9CH3 OH CH3 CH39CH9CH29CH9CH3 CH3 OH CH29CH29OH OH CH39CH9CH3 C9CH3 O CH39CH9CH29C9OH CH3 O CH39CH9C9CH3 O CH39CH29C9C9OH O O O CH39CH29CH29C9OH O CH39C9CH29CH29CH3 O 184 Chapter 14 46475_14_p174-186 4/12/06 8:31 AM Page 184 c. 14.64 a. b. c. 14.65 a. acetal; propanal and methanol b. hemiacetal; butanone and ethanol c. acetal; cyclohexanone and ethanol 14.66 a. hemiacetal; propanal and methanol b. hemiacetal; cyclohexanone and 2-propanol c. acetal; ethanal (acetaldehyde) and 1-propanol 14.67 1. true 2. false 3. true 4. true 5. false 6. true 7. true 14.68 a. b. 485 mL H2 14.69 CH3¬CH2¬CH2¬OH A 1-propanol CH3¬CH"CH2 B propene C propanal O CH39CH29C9H 1.56 g butanone * 1 mole butanone 72.0 g butanone * 1 mole H2 1 mole butanone * 22.4 L 1 mole H2 * 1000 mL 1 L = O OH Pt CH39C9CH29CH3
H2 CH39CH9CH29CH3 OH
H2O H
oxidation O OH O [O] CH39CH29CH9CH3 CH39CH29C9CH3 CH39CH29CH"CH2
H2OCH39CH29CH29CH29OH H
, heat H
CH39CH29CH29CH29CH29OH CH39CH29CH29CH"CH2 H
, heat O Ni CH39CH29CH29CH29C9H
H2 butanone OOH [O] CH39CH29CH"CH2
H2O CH39CH29CH9CH3 CH39CH29C9CH3 butanal O Ni CH39CH29CH29C9H
H2 CH39CH29CH29CH29OH H
, heat Br CH39CH29CH"CH2
Br2 CH39CH29CH9CH29Br 185 Aldehydes, Ketones, and Chiral Molecules 46475_14_p174-186 4/12/06 8:31 AM Page 185