Principles of Chem II
Principles of Chem II CHEM 1212
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Date Created: 10/12/15
4647571431747186 41206 831AM Page 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 141 Aldehydes and Ketones Enviranmental Nate Vanilla Health Nate Same Impartant Aldehydes and Ketanes 142 Physical Properties 143 Oxidation and Reduction 144 Addition Reactions 145 Chiral Molecules Health Nate Enantiamers in Bialagical 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 andor ketones on the labels of products such as mouthwash antifreeze rubbing alcohol food avorings 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 nd the mirror image among the models and compare the two Or I ask students to now make a mirror image of the rst model Eventually this hands on visual approach 174 4647571431747186 41206 831AM Page 175 Aldehydes Ketones and Chiral Molecules helps students to understand the three dimensional relationship between mirror images that is dif cult to show in two dimensions I make some larger models with an OH group aldehyde group CH3 group and CHZOH 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 Identi cation of an Unknown Laboratory Skills to Demonstrate Proper technique for noting the odor of a substance in a test tube Identi cation of a change in the orange color of chromic acid to green as an indication of the occurrence of an oxidation reaction Identi cation of changes in the iodoform test Identi cation 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 Identi cation of a change in the orange color of chromic acid to green as an indication of the occurrence of an oxidation reaction Identi cation of changes in the iodoform test Answers and Solutions to Selected Text Problems 141 a ketone b aldehyde c ketone d aldehyde 142 a aldehyde b aldehyde c ketone d ketone 175 4647571431747186 41206 831AM Page 176 Chapter 14 143 a 1 b 144 a 3 b 145 a propanal b d 2 pentanone e 146 a u b d cyclopentanone e 147 a acetaldehyde b 148 a ethyl methyl ketone Cu 149 a CH3 C H Br Br 0 1410 1411 1412 1413 176 a 9 or CH3 CH CH C H CH3 4 l c2 3 cl 2 methyl 3 pentanone 3 methylcyclohexanone 4 methyl 2 pentanone 37 4 c 3 bromobutanal f 4 chlorobenzaldehyde c 5 methyl 3 hexanone f q 1 methyl propyl ketone b diethyl ketone O c formaldehyde c propionaldehyde CH3 b CH3 C CH2 CH CH3 O CH3 CH2 CH CH2 C H Cu CH3 CH2 C H c1 Cl 0 CH3 CH2 CH CH CH2 C H Cu CH3 C CH3 CHO OCH3 CHO OCH3 0 CH3 C CH3 has a polar carbonyl group Pentanal has more carbons and thus a higher molar mass l butanol hydrogen bonds with other l butanol molecules 4 H d CH3 C CH2 CH2 CHz CH3 O b CH3 CH2 CH2 c H H d CHz C CHz CHz Br 4647571431747186 41206 831AM Page 177 Aldehydes Ketones and Chiral Molecules 1414 2 butanol molecules can hydrogen bond with each other The carbonyl group in butanone molecules provides dipole dipole interactions Pentanone has a greater molar mass 9 II CH3 C C CH3 more hydrogen bonding acetaldhyde acetaldehyde can hydrogen bond acetone lower number of carbon atoms 1415 97 1416 Propanal the carbonyl group hydrogen bonds with water Propanone has fewer carbon atoms Propanone the carbonyl group hydrogen bonds with water PF 1417 No The carbon chain diminishes the effect of the carbonyl group 1418 Yes Carbonyl compounds with one to four carbon atoms are soluble in water The alkyl group in aldehydes with ve or more carbon atoms diminishes the polar effect of the carbonyl group 1419 a An aldehyde is the product of the oxidation of a primary alcohol CH3OH b A ketone is the product of the oxidation of a secondary alcohol OH c A ketone is the product of the oxidation of a secondary alcohol OH CH3 CH CH2 CH3 d An aldehyde is the product of the oxidation of a primary alcohol CHZOH e A ketone is the product of the oxidation of a secondary alcohol CH3 cm OH 1420 a CH3 CH2 OH b CH3 CH CH CH3 OH 0 1 CH3 CH2 CH2 OH CH3 e CH3 CH CH2 CH2 OH 177 4647571431747186 41206 831AM Page 178 Chapter 14 1421 a A primary alcohol will be oxidized to an aldehyde and then to a carboxylic acid H Cu CH3 CH2 CH2 CH2 C H then CH3 CH2 CH2 CH2 C OH 0 II b A secondary alcohol will be oxidized to a ketone CH3 CH2 C CH3 c A secondary alcohol will be oxidized to a ketone O 0 CH3 1 A secondary alcohol will be oxidized to a ketone CH3 C CH2 CH CH3 e A primary alcohol will be oxidized to an aldehyde and then to a carboxylic acid 1H3 Cu 1H3 CH3 CH CH2 C H then CH3 CH CH2 C OH if CH3 Cu 1422 a C H b CH3 CH CH2 C CH3 if c none 1 CH3 C C CH2 CH3 O g 1423 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 Acetone is a three carbon ketone it will be reduced to a three carbon secondary alcohol OH ET CH3 CH CH3 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 Br CH3 CH2 CH2 CH CH2 CH2 OH 2 methy1 3 pentanone is a ve carbon ketone with a methyl group attached to carbon 2 It will be reduced to a ve carbon secondary alcohol with a methyl attached to carbon 2 CH3 OH CH3 CH CH CH2 CH3 F39 178 4647571431747186 41206 831AM Page 179 1424 1425 1426 1427 1428 1429 1430 1431 Aldehydes Ketones and Chiral Molecules OH a CH3 CH2 CH CH2 CH2 CH3 b CH3OH OH OH 0 d CH3 IZH CH2 CH2 CH3 c1 OH OH a CH3 IZ H b H Cl H EH EH CH CH a CH3 CH2 C H b CHz C CH3 OH OH a hemiacetal ethanol and formaldehyde b hemiacetal c acetal d hemiacetal e t a neither b neither c hemiacetal d acetal e neither A hemiacetal forms when an alcohol is added to the carbonyl of an aldehyde or ketone O CH3 C CH3 a CH3 C H b CH3 C CH3 OH OH HO OCH3 o CH3 c d CH3 CH2 CH2 IZ H ckH O CHz CH3 O CHz CH3 a CH3 CH2 C H b CH3 CH2 C CH3 OH OH HO O CHz CH3 OCH2CH3 c d H Cl H OH An acetal forms when a second molecule of alcohol reacts with a hemiacetal cl CH3 Cgt CH3 a CH3 II H b CH3 IZ CH3 o CH3 O CH3 179 4647571431747186 42706 727AM Page 180 Chapter 14 CH3O OCH3 ClCH3 c d CH3 CH2 CH2 II H O CH3 0 CH2 CH3 C CH2 CH3 1432 a CH3 CH2 C H b CH3 CH2 C CH3 O CHz CH3 CH2 CH3 CH3 CH2 O 0 CH2 CH3 C CH2 CH3 c d H C H d CH2 CH3 Br chiral carban 1433 a achiral b chiral CH3 CH CH2 CH3 chiral carban Br 0 g I ll c chiral CH3 CH C H d achiral 1434 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 1 Chiral carbon 2 is bonded to a chlorine atom hydrogen atom methyl group and a CH2 Br group CH3 chiral carban 1435 a CH3 CCH CHz CHz CH CHz CHz OH IZH3 O b HzN CH C OH chiral carban CH IZH3 HO CH CHz NHZ 1436 a CH2gtCHWZ b IQ HO H CH3 CH0 1437 a H0Br b C1Br c H0H CH3 OH CHZCH3 1 80 4647571431747186 41206 831AM Page 181 Aldehydes Ketones and Chiral Molecules 1438 a H b CH3 c CHO HO Br H OH HO H CHZOH CHZOH CHZOH 1439 a identical b enantiomers c identical 1 enantiomers 1440 a enantiomers b identical c enantiomers d enantiomers 1441 a b and f will give positive Tollen s tests 1442 a 37 dimethyl 6 octenal b The fen signi es a double bond c The ial signi es an aldehyde 1 CIOngO 14 02 gt 10 C02 9 H20 1443 a aromatic aldehyde b aromatic aldehyde ether phenol c aromatic aldehyde alkene d cycloalkane ketone e ketone a 2 b 5 c d 3 e O O 1444 a CH3 C CH2 CH2 CH2 CHz CH3 0 CH3 CH3 1 l b CH3 H C CHz CHZ H CH3 o H o c H Z ZC CH2 CH2 CH3 HW l o o d H CH CH2 CH2 CHC CH3 H 143 CH3 Cu CH3 Cu Cu 1445 CH3 CH2 CH2 C H CH3 CH C H CH3 CH2 C CH3 1446 The CO double bond has a dipole because the oxygen atom is strongly electronegative compared with the carbon atom 1447 aquotbrm4 1 1x4 111er I 1 n1 1 c39 339CthTOPTOPanal d 5 chloro 3 hexanone e 2 chloro 3 pentanone 1448 a butanone ethyl methyl ketone b 35 dichlorobenzaldehyde c l chlorocyclopentanone d 34 dimethylpentanal e methyl phenyl ketone 181 4647571431747186 41206 831AM Page 182 Chapter 14 1449 a 3 methylcyclopentanone is a ve carbon cyclic structure with a methyl group located two carbons from the carbonyl group 0 CH3 ET p chlorobenzaldehyde is a benzene with an aldehyde group and a chlorine on carbon 4 CH0 Cl 9 3 chloropropionaldehyde is a three carbon aldehyde with a chlorine located two carbons from the carbonyl group Cu Cl CHz CHz C H Butanone is a four carbon ketone 0 II F39 CH3 C CH2 CH3 This is a six carbon aldehyde with a methyl group on carbon 3 CH3 CH3 CH2 CH2 CH CH2 C H 5 Cu 1 Cu 1450 a CH3 CH2 C H b CH3 CH2 CH C H 0 CH3 CH3 0 CH3 c d CH3 CH CH2 CH CH2 C H 0 Br 1451 Compounds b c and d are soluble in water because they have polar groups with oxygen atoms that hydrogen bond with water and fewer than ve carbon atoms 1452 Compounds a b and c are soluble in water because they have polar groups with oxygen atoms that hydrogen bond with water and fewer than ve carbon atoms 182 4647571431747186 41206 831AM Page 183 1453 1454 1455 1456 1457 1458 1459 a CH3 CH2 Aldehydes Ketones and Chiral Molecules OH polar OH group can hydrogen bond II b CH3 CH2 C H polar carbonyl group C CH3 CH2 CH2 OH polar OH group can hydrogen bond 0 a CH3 CH2 CH2 CH2 C H greater molar mass of the two carbonyl compounds b CH3 C CH3 dipole dipole interactions increased boiling point compared with an alkane CH c CH3 CH CH3 the OH can form hydrogen bonds A chiral carbon is bonded to four different groups 3911 Cl a H II O H b none c none Cl H NHZ C Br 1 CH34 C H e CH3 CH24 j1 CH2 CH2 CH3 f none a none OH C b CH3 i C CH3 c none 1 none Br e CH3 CHz CH3 OH f none Enantiomers are mirror images a identical b enantiomers c enantiomers tum 180 1 enantiomers a enantiomers b identical c identical 1 enantiomers Primary alcohols oxidize to aldehydes and then to carboxylic acids Secondary alcohols oxidize to ketones II a CH3 CH2 C H further oxidation gt H CH3 CH2 C OH 183 4647571431747186 41206 831AM Page 184 4 Chapter 14 1460 a 1461 1462 1463 184 F39 F 9 a Cu CH3 C CH2 CH2 CH3 Cu CH3 CH2 CH2 C OH o 0 CH3 CH2 C C OH Cu CH3 CH C CH3 CH3 c CH3 CH CH2 C OH UC Cm OH CH3 CH CH3 CH2 CH2 OH CH3 CH CH3 CH CH2 CH CH3 O CH3 CH2 OH b OH c CH3 OH CH3 OH O H 0 CH3 CHCH2 H20 CH3 CH CH3 propene H N39 CH3 CH2 CH2 C H H2 41gt CH3 CH2 CH2 CH2 CH3 C CH3 propanone 2 heat H OH gt 4647571431747186 41206 831AM Page 185 Aldehydes Ketones and Chiral Molecules Illr CH3 CH2 CHCH2 Brz CH3 CH2 CH CH2 Br Ni Ht heat c CH3 CH2 CH2 C H Hz CH3 CH2 CH2 CH2 OH gt butanal OH I 0 ll CH3 CH2 CHCH2 HZO CH3 CH2 CH CH3 4gt CH3 CH2 C CH3 butanone Ni 1464 a CH3 CH2 CH2 CH2 C H Hz Hh t CH3 CH2 CH2 CH2 CH2 0Hi CH3 CH2 CH2 CHCH2 Ht h t 14 b CH3 CH2 CH2 CH2 OH A CH3 CH2 CHCH2 HZO 4gt OH C 0 CH3 CH2 CH CH3 Q CH3 CH2 C CH3 OH 0 Hr oxidation acetal propanal and methanol hemiacetal butanone and ethanol acetal cyclohexanone and ethanol 9 1465 927 1466 a hemiacetal propanal and methanol b hemiacetal cyclohexanone and 2 propanol c 1 acetal ethanal acetaldehyde and l propanol 1467 true 2 false 3 true 4 true 5 false 6 true 7 true H OH Pt 1468 a CH3 C CH2 CH3 H2 4gt CH3 CH CH2 CH3 ne lmele HE 2242 X lOOOmL l mole 13W b 156 x x x W 720 We 1Mue 1M2 IE 485 mL H2 1469 CH3 CH2 CH2 OH Al propanol CH3 CHCH2 Bpropene Cu CH3 CHz C H C propanal 185