Dr. Wolf's CHM 201 & Chapter 17 Aldehydes and Ketones. Nucleophilic Addition to the Carbonyl Group

Dr. Wolf's CHM 201 & NomenclatureNomenclature

Dr. Wolf's CHM 201 & IUPAC Nomenclature of Aldehydes HOOH OHCCHCHO Base the name on the chain that contains the carbonyl group and replace the -e ending of the hydrocarbon by -al.

Dr. Wolf's CHM 201 & ,4-dimethylpentanal 5-hexenal IUPAC Nomenclature of Aldehydes HOOH OHCCHCHO 2-phenylpropanedial (keep the -e ending before -dial)

Dr. Wolf's CHM 201 & when named as a substituent formyl group carbaldehyde or carboxaldehyde when named as a suffix C HO IUPAC Nomenclature of Aldehydes

Dr. Wolf's CHM 201 & CH 3 CH 2 CCH 2 CH 2 CH 3 O CH 3 CHCH 2 CCH 3 O CH 3 H3CH3CH3CH3C O Base the name on the chain that contains the carbonyl group and replace -e by -one. Number the chain in the direction that gives the lowest number to the carbonyl carbon. Substitutive IUPAC Nomenclature of Ketones

Dr. Wolf's CHM 201 & Substitutive IUPAC Nomenclature of Ketones CH 3 CH 2 CCH 2 CH 2 CH 3 O CH 3 CHCH 2 CCH 3 O CH 3 H3CH3CH3CH3C O 3-hexanone 4-methyl-2-pentanone 4-methylcyclohexanone

Dr. Wolf's CHM 201 & Functional Class IUPAC Nomenclature of Ketones CH 3 CH 2 CCH 2 CH 2 CH 3 OO CH 2 CCH 2 CH 3 CH CH 2 O H2CH2CH2CH2C CHC List the groups attached to the carbonyl separately in alphabetical order, and add the word ketone.

Dr. Wolf's CHM 201 & CH 3 CH 2 CCH 2 CH 2 CH 3 O ethyl propyl ketone benzyl ethyl ketone divinyl ketone O CH 2 CCH 2 CH 3 CH CH 2 O H2CH2CH2CH2C CHC Functional Class IUPAC Nomenclature of Ketones

Dr. Wolf's CHM 201 & Structure and Bonding: The Carbonyl Group

Dr. Wolf's CHM 201 & planar bond angles: close to 120° C=O bond distance: 122 pm Structure of Formaldehyde

Dr. Wolf's CHM 201 & butene propanal The Carbonyl Group O dipole moment = 0.3D dipole moment = 2.5D very polar double bond

Dr. Wolf's CHM 201 & kJ/mol 2442 kJ/mol Alkyl groups stabilize carbonyl groups the same way they stabilize carbon-carbon double bonds, carbocations, and free radicals. heat of combustion Carbonyl group of a ketone is more stable than that of an aldehyde O OH

Dr. Wolf's CHM 201 & Heats of combustion of C 4 H 8 isomeric alkenes CH 3 CH 2 CH=CH kJ/mol cis-CH 3 CH=CHCH kJ/mol trans-CH 3 CH=CHCH kJ/mol (CH 3 ) 2 C=CH kJ/mol 2475 kJ/mol 2442 kJ/mol O OH Spread is greater for aldehydes and ketones than for alkenes

Dr. Wolf's CHM 201 & nucleophiles attack carbon; electrophiles attack oxygen Resonance Description of Carbonyl Group C O C O +–

Dr. Wolf's CHM 201 & Carbon and oxygen are sp 2 hybridized Bonding in Formaldehyde

Dr. Wolf's CHM 201 & The half-filled p orbitals on carbon and oxygen overlap to form a  bond Bonding in Formaldehyde

Dr. Wolf's CHM 201 & Physical Properties

Dr. Wolf's CHM 201 & boiling point –6°C 49°C 97°C Aldehydes and ketones have higher boiling than alkenes, but lower boiling points than alcohols. More polar than alkenes, but cannot form intermolecular hydrogen bonds to other carbonyl groups O OH

Dr. Wolf's CHM 201 & Sources of Aldehydes and Ketones

Dr. Wolf's CHM 201 & heptanone (component of alarm pheromone of bees) O Many aldehydes and ketones occur naturally

Dr. Wolf's CHM 201 & trans-2-hexenal (alarm pheromone of myrmicine ant) Many aldehydes and ketones occur naturally O H

Dr. Wolf's CHM 201 & citral (from lemon grass oil) Many aldehydes and ketones occur naturally O H

Dr. Wolf's CHM 201 & from alkenes ozonolysis from alkynes hydration (via enol) from arenes Friedel-Crafts acylation from alcohols oxidation Synthesis of Aldehydes and Ketones A number of reactions already studied provide efficient synthetic routes to aldehydes and ketones.

Dr. Wolf's CHM 201 & COR OH aldehydes from carboxylic acids RCH 2 OH 1. LiAlH 4 2. H 2 O PDC, CH 2 Cl 2 H COR What about..?

Dr. Wolf's CHM 201 & benzaldehyde from benzoic acid COHO CHO 1. LiAlH 4 2. H 2 O PDC CH 2 Cl 2 CH 2 OH (81%) (83%) ExampleExample

Dr. Wolf's CHM 201 & COR H ketones from aldehydes R' COR PDC, CH 2 Cl 2 1. R'MgX 2. H 3 O + RCHR' OH What about..?

Dr. Wolf's CHM 201 & C O CH 3 CH 2 H 3-heptanone from propanal H 2 CrO 4 1. CH 3 (CH 2 ) 3 MgX 2. H 3 O + CH 3 CH 2 CH(CH 2 ) 3 CH 3 OH O CH 3 CH 2 C(CH 2 ) 3 CH 3 (57%) ExampleExample

Dr. Wolf's CHM 201 & Reactions of Aldehydes and Ketones: A Review and a Preview

Dr. Wolf's CHM 201 & Already covered in earlier chapters: reduction of C=O to CH 2 Clemmensen reduction Wolff-Kishner reduction reduction of C=O to CHOH addition of Grignard and organolithium reagents Reactions of Aldehydes and Ketones

Dr. Wolf's CHM 201 & Principles of Nucleophilic Addition to Carbonyl Groups: Hydration of Aldehydes and Ketones

Dr. Wolf's CHM 201 & H2OH2OH2OH2O Hydration of Aldehydes and Ketones C O HO C O H

Dr. Wolf's CHM 201 & compared to H electronic: alkyl groups stabilize reactants steric: alkyl groups crowd product OHOH R R' + H2OH2OH2OH2O C C R R' O Substituent Effects on Hydration Equilibria

Dr. Wolf's CHM 201 & C=OhydrateK%Relative rate CH 2 =OCH 2 (OH) > CH 3 CH=OCH 3 CH(OH) (CH 3 ) 3 CCH=O(CH 3 ) 3 CCH(OH) (CH 3 ) 2 C=O(CH 3 ) 2 C(OH) Equilibrium Constants and Relative Rates of Hydration

Dr. Wolf's CHM 201 & when carbonyl group is destabilized alkyl groups stabilize C=O electron-withdrawing groups destabilize C=O When does equilibrium favor hydrate?

Dr. Wolf's CHM 201 & OH OH R R + H2OH2OH2OH2O C C R RO Substituent Effects on Hydration Equilibria R = CH 3 : K = R = CF 3 : K = 22,000

Dr. Wolf's CHM 201 & Mechanism of Hydration (base) C O O H – Step 1: + HO C O –

Dr. Wolf's CHM 201 & Mechanism of Hydration (base) Step 2: O HH HO C O – + O H – HO C OHOHOHOH

Dr. Wolf's CHM 201 & Mechanism of Hydration (acid) C O Step 1: + HOH H + + C OHOHOHOH + H O H

Dr. Wolf's CHM 201 & Mechanism of Hydration (acid) Step 2: C OHOHOHOH + + HO H C OHOHOHOH HO H +

Dr. Wolf's CHM 201 & Mechanism of Hydration (acid) Step 3: + HO H C OHOHOHOH H OH O H C OHOHOHOH + H H OH +

Dr. Wolf's CHM 201 & Cyanohydrin Formation

Dr. Wolf's CHM 201 & Cyanohydrin Formation CO HCN H C O NC

Dr. Wolf's CHM 201 & Cyanohydrin Formation CO C–N

Dr. Wolf's CHM 201 & Cyanohydrin Formation – O NC C HH H + O H H O O NC C H

Dr. Wolf's CHM 201 & ,4-Dichlorobenzaldehyde cyanohydrin (100%) ExampleExampleClCl CH OClCl CHCN OH NaCN, water then H 2 SO 4

Dr. Wolf's CHM 201 & ExampleExample CH 3 CCH 3 O NaCN, water then H 2 SO 4 CH 3 CCH 3 OHCN (77-78%)

Dr. Wolf's CHM 201 & Acetal Formation

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Enamine formation Compounds related to imines The Wittig reaction

Dr. Wolf's CHM 201 & Recall Hydration of Aldehydes and Ketones HOH C O HO C O H RR' R R'

Dr. Wolf's CHM 201 & Alcohols Under Analogous Reaction with Aldehydes and Ketones R"OH C O RR' R"O C O H R R' Product is called a hemiacetal.

Dr. Wolf's CHM 201 & Product is called a hemiacetal. ROH, H + Hemiacetal reacts further in acid to yield an acetal R"O C O H RR' R"O C OR RR' Product is called an acetal.

Dr. Wolf's CHM 201 & HCl 2CH 3 CH 2 OH + + H 2 O Benzaldehyde diethyl acetal (66%) ExampleExample CHO CH(OCH 2 CH 3 ) 2

Dr. Wolf's CHM 201 & HOCH 2 CH 2 OH + CH 3 (CH 2 ) 5 CH O p-toluenesulfonic acid benzene + H2OH2OH2OH2O (81%) H (CH 2 ) 5 CH 3 H2CH2CH2CH2C CH 2 O O C Diols Form Cyclic Acetals

Dr. Wolf's CHM 201 & In general: Position of equilibrium is usually unfavorable for acetal formation from ketones. Important exception: Cyclic acetals can be prepared from ketones.

Dr. Wolf's CHM 201 & HOCH 2 CH 2 OH +O p-toluenesulfonic acid benzene + H2OH2OH2OH2O H2CH2CH2CH2C CH 2 O O C (78%) C 6 H 5 CH 2 CCH 3 CH 3 C 6 H 5 CH 2 ExampleExample

Dr. Wolf's CHM 201 & First stage is analogous to hydration and leads to hemiacetal acid-catalyzed nucleophilic addition of alcohol to C=O Mechanism of Acetal Formation

Dr. Wolf's CHM 201 & MechanismMechanism C O HH R + O

Dr. Wolf's CHM 201 & MechanismMechanism C O H R O H +

Dr. Wolf's CHM 201 & MechanismMechanism C O H +RH O

Dr. Wolf's CHM 201 & MechanismMechanism C O O H + R H O RH

Dr. Wolf's CHM 201 & MechanismMechanism +HO RH C O O H R

Dr. Wolf's CHM 201 & Second stage is hemiacetal-to-acetal conversion involves carbocation chemistry Mechanism of Acetal Formation

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage C O O H R HH R + O

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage HR O C O O H R H +

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage O O H R + H C

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage C O R + O HH

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage C O R + Carbocation is stabilized by delocalization of unshared electron pair of oxygen C OR +

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage C O R + O H R

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage C O R + O H R O HR

Dr. Wolf's CHM 201 & Hemiacetal-to-acetal Stage + H O HR C O R O R

Dr. Wolf's CHM 201 & C R R'O 2R"OH + OR" R R' C + H 2 O mechanism: reverse of acetal formation; hemiacetal is intermediate application: aldehydes and ketones can be "protected" as acetals. Hydrolysis of Acetals

Dr. Wolf's CHM 201 & Acetals as Protecting Groups

Dr. Wolf's CHM 201 & The conversion shown cannot be carried out directly... CH CH 3 CCH 2 CH 2 C O CCH 3 CH 3 CCH 2 CH 2 C O 1. NaNH 2 2. CH 3 I ExampleExample

Dr. Wolf's CHM 201 & because the carbonyl group and the carbanion are incompatible functional groups. C:C:C:C: CH 3 CCH 2 CH 2 C O–

Dr. Wolf's CHM 201 & ) protect C=O 2) alkylate 3) restore C=O 1) protect C=O 2) alkylate 3) restore C=O StrategyStrategy

Dr. Wolf's CHM 201 & HOCH 2 CH 2 OH + p-toluenesulfonic acid benzene H2CH2CH2CH2C CH 2 O O C CH 3 CH 3 CCH 2 CH 2 C O CH CH 2 CH 2 C CH Example: Protect

Dr. Wolf's CHM 201 & H2CH2CH2CH2C CH 2 O O C CH 3 CH 2 CH 2 C CH 1. NaNH 2 2. CH 3 I H2CH2CH2CH2C CH 2 O O C CH 3 CH 2 CH 2 C CCH 3 Example: Alkylate

Dr. Wolf's CHM 201 & H2CH2CH2CH2C CH 2 O O C CH 3 CH 2 CH 2 C CCH 3 H2OH2OH2OH2O HCl HOCH 2 CH 2 OH (96%) CCH 3 CH 3 CCH 2 CH 2 C O+ Example: Deprotect

Dr. Wolf's CHM 201 & Reaction with Primary Amines: Imines

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & H2NH2NH2NH2N R C O + H a carbinolamine CO HNHNHNHN R N R C + H 2 O (imine) Imine (Schiff's Base) Formation

Dr. Wolf's CHM 201 & CH 3 NH 2 CHO+ CH=NCH 3 + H 2 O N-Benzylidenemethylamine (70%) ExampleExample

Dr. Wolf's CHM 201 & CH 3 NH 2 CHO+ CH=NCH 3 + H 2 O N-Benzylidenemethylamine (70%) ExampleExample CH OHOHOHOH NHCH 3

Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH 2 NH 2 O + + H 2 O N-Cyclohexylideneisobutylamine (79%) NCH 2 CH(CH 3 ) 2 ExampleExample

Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH 2 NH 2 O + + H 2 O N-Cyclohexylideneisobutylamine (79%) NCH 2 CH(CH 3 ) 2 OHOHOHOH NHCH 2 CH(CH 3 ) 2 ExampleExample

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & Reaction with Derivatives of Ammonia H2NH2NH2NH2NG + R2CR2CR2CR2C O R2CR2CR2CR2C NGNGNGNG+ H2OH2OH2OH2O H2NH2NH2NH2NOH R2CR2CR2CR2C NOH hydroxylamineoxime

Dr. Wolf's CHM 201 & CH 3 (CH 2 ) 5 CH + H 2 NOH O CH 3 (CH 2 ) 5 CH + H 2 O NOH (81-93%) ExampleExample

Dr. Wolf's CHM 201 & Reaction with Derivatives of Ammonia H2NH2NH2NH2NG + R2CR2CR2CR2C O R2CR2CR2CR2C NGNGNGNG+ H2OH2OH2OH2O H2NH2NH2NH2NOH R2CR2CR2CR2C NOH hydroxylamineoxime H2NH2NH2NH2N NH 2 R2CR2CR2CR2C NNH 2 hydrazinehydrazone etc.

Dr. Wolf's CHM 201 & H 2 NNH 2 + H 2 O (73%) ExampleExampleOC NNH 2 C

Dr. Wolf's CHM 201 & CCH 3 ExampleExampleO + H 2 NNH phenylhydrazine + H 2 O CCH 3 NNH a phenylhydrazone (87-91%)

Dr. Wolf's CHM 201 & CH 3 (CH 2 ) 9 CCH 3 O H 2 NNHCNH 2 O + H2OH2OH2OH2O CH 3 (CH 2 ) 9 CCH 3 NNHCNH 2 O+ ExampleExample semicarbazide a semicarbazone (93%)

Dr. Wolf's CHM 201 & Reaction with Secondary Amines: Enamines

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & R2NHR2NHR2NHR2NH + H 2 O (enamine) C R2NR2NR2NR2N C Enamine Formation C O R2NR2NR2NR2N H H C C O H C

Dr. Wolf's CHM 201 & (heat in benzene) ExampleExampleO NHNHNHNH via OHOHOHOH N (80-90%) N

Dr. Wolf's CHM 201 & The Wittig Reaction

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & Some reactions of aldehydes and ketones progress beyond the nucleophilic addition stage Acetal formation Imine formation Compounds related to imines Enamines The Wittig reaction

Dr. Wolf's CHM 201 & The Wittig Reaction Synthetic method for preparing alkenes. One of the reactants is an aldehyde or ketone. The other reactant is a phosphorus ylide. (C 6 H 5 ) 3 P C +AB – (C 6 H 5 ) 3 P CAB A key property of ylides is that they have a negatively polarized carbon and are nucleophilic.

Dr. Wolf's CHM 201 & Figure Charge distribution in a ylide

Dr. Wolf's CHM 201 & The Wittig Reaction (C 6 H 5 ) 3 P C +AB – + + CC R R' A B (C 6 H 5 ) 3 P O + – CORR'

Dr. Wolf's CHM 201 & ExampleExample + + (C 6 H 5 ) 3 P O+ – (C 6 H 5 ) 3 P CH 2 +– O DMSO (86%) dimethyl sulfoxide (DMSO) or tetrahydrofuran (THF) is the customary solvent

Dr. Wolf's CHM 201 & MechanismMechanism CORR' P(C 6 H 5 ) 3 + CAB – OC C RR' B A Step 1

Dr. Wolf's CHM 201 & MechanismMechanism OC C P(C 6 H 5 ) 3 RR' B A Step 2 P(C 6 H 5 ) 3 + – O R'RA B C C +

Dr. Wolf's CHM 201 & Planning an Alkene Synthesis via the Wittig Reaction

Dr. Wolf's CHM 201 & Retrosynthetic Analysis There will be two possible Wittig routes to an alkene. Analyze the structure retrosynthetically. Disconnect the doubly bonded carbons. One will come from the aldehyde or ketone, the other from the ylide. CCRR' A B

Dr. Wolf's CHM 201 & Retrosynthetic Analysis of Styrene C 6 H 5 CH CH 2 HCH O + (C 6 H 5 ) 3 P CHC 6 H 5 + – C 6 H 5 CH O+ (C 6 H 5 ) 3 P CH 2 + – Both routes are acceptable.

Dr. Wolf's CHM 201 & Preparation of Ylides Ylides are prepared from alkyl halides by a two-stage process. The first step is a nucleophilic substitution. Triphenylphosphine is the nucleophile. (C 6 H 5 ) 3 P + CHAB X + (C 6 H 5 ) 3 P CHAB + X–X–X–X–

Dr. Wolf's CHM 201 & Preparation of Ylides In the second step, the phosphonium salt is treated with a strong base in order to remove a proton from the carbon bonded to phosphorus. (C 6 H 5 ) 3 P CAB + H base – (C 6 H 5 ) 3 P CAB + – H base

Dr. Wolf's CHM 201 & Preparation of Ylides Typical strong bases include organolithium reagents (RLi), and the conjugate base of dimethyl sulfoxide as its sodium salt [NaCH 2 S(O)CH 3 ]. (C 6 H 5 ) 3 P CAB + H base (C 6 H 5 ) 3 P C A B + – – Hbase

Dr. Wolf's CHM 201 & Stereoselective Addition to Carbonyl Groups Nucleophilic addition to carbonyl groups sometimes leads to a mixture of stereoisomeric products.

Dr. Wolf's CHM 201 & % ExampleExample CH 3 H3CH3CH3CH3CO 80% OHOHOHOH H H3CH3CH3CH3C OHOHOHOH H H3CH3CH3CH3C NaBH 4

Dr. Wolf's CHM 201 & this methyl group hinders approach of nucleophile from top H 3 B—H – preferred direction of approach is to less hindered (bottom) face of carbonyl group preferred direction of approach is to less hindered (bottom) face of carbonyl group Steric Hindrance to Approach of Reagent

Dr. Wolf's CHM 201 & Biological reductions are highly stereoselective pyruvic acid  S-(+)-lactic acid O CH 3 CCO 2 H NADH H+H+H+H+ enzyme is lactate dehydrogenase CO 2 H HOHOHOHO H CH 3

Dr. Wolf's CHM 201 & Figure One face of the substrate can bind to the enzyme better than the other.

Dr. Wolf's CHM 201 & Figure Change in geometry from trigonal to tetrahedral is stereoselective. Bond formation occurs preferentially from one side rather than the other.

Dr. Wolf's CHM 201 & in aqueous solution RCH RCH RCOHOOH OH H2OH2OH2OH2OO Oxidation of Aldehydes

Dr. Wolf's CHM 201 & K 2 Cr 2 O 7 H 2 SO 4 H2OH2OH2OH2O O O CH O O COH (75%) via O OH CH OH ExampleExample

Dr. Wolf's CHM 201 & The Baeyer-Villiger Oxidation of Ketones Oxidation of ketones with peroxy acids gives esters by a novel rearrangement.

Dr. Wolf's CHM 201 & R"COOH O RCR' O + R"COH O + KetoneEster ROCR' O GeneralGeneral

Dr. Wolf's CHM 201 & C 6 H 5 COOH O (67%) Oxygen insertion occurs between carbonyl carbon and larger group. Methyl ketones give acetate esters. CHCl 3 ExampleExample CCH 3 O OCCH 3 O

Dr. Wolf's CHM 201 & C 6 H 5 COOH O (66%) Reaction is stereospecific. Oxygen insertion occurs with retention of configuration. CHCl 3 StereochemistryStereochemistry O CCH 3 H3CH3CH3CH3C HH OCCH 3 O H3CH3CH3CH3C HH

Dr. Wolf's CHM 201 & R"COOH O RCR' O + ROCR' O R"COH O + First step is nucleophilic addition of peroxy acid to the carbonyl group of the ketone. O O C O H R R' OCR" MechanismMechanism

Dr. Wolf's CHM 201 & R"COOH O RCR' O + ROCR' O R"COH O + O O C OHR R' OCR" Second step is migration of group R from carbon to oxygen. The weak O—O bond breaks in this step. MechanismMechanism

Dr. Wolf's CHM 201 & Certain bacteria use hydrocarbons as a source of carbon. Oxidation proceeds via ketones, which then undergo oxidation of the Baeyer-Villiger type. Biological Baeyer-Villliger Oxidation O bacterial oxidation O O O 2. cyclohexanone monooxygenase, coenzymes

Dr. Wolf's CHM 201 & Spectroscopic Analysis of Aldehydes and Ketones

Dr. Wolf's CHM 201 & Presence of a C=O group is readily apparent in infrared spectrum C=O stretching gives an intense absorption at cm-1 In addition to peak for C=O, aldehydes give two weak peaks near 2720 and 2820 nm for H—C=O Infrared Spectroscopy

Dr. Wolf's CHM 201 & Francis A. Carey, Organic Chemistry, Fifth Edition. Copyright © 2003 The McGraw-Hill Companies, Inc. All rights reserved Wave number, cm -1 Figure Infrared Spectrum of Butanal C=O CH 3 CH 2 CH 2 CH=O H—C=O 2720 cm cm cm -1

Dr. Wolf's CHM 201 & Aldehydes: H—C=O proton is at very low field (  9-10 ppm). Methyl ketones: CH 3 singlet near  2 ppm. 1 H NMR

Dr. Wolf's CHM 201 & Chemical shift ( , ppm) HCO CH(CH 3 ) 2

Dr. Wolf's CHM 201 & Chemical shift ( , ppm) CH 3 CO CH 3 CH 2

Dr. Wolf's CHM 201 & C NMR Carbonyl carbon is at extremely low field-near  200 ppm Intensity of carbonyl carbon is usually weak

Dr. Wolf's CHM 201 & Chemical shift ( , ppm) CH 3 CH 2 CCH 2 CH 2 CH 2 CH 3 O

Dr. Wolf's CHM 201 & UV-VISUV-VIS Aldehydes and ketones have two bands in the UV region:  * and n  *  *: excitation of a bonding  electron to an antibonding  * orbital  *: excitation of a nonbonding electron on oxygen to an antibonding  * orbital

Dr. Wolf's CHM 201 & UV-VISUV-VIS H3CH3CH3CH3C H3CH3CH3CH3C C O  * max 187 nm n  * max 270 nm

Dr. Wolf's CHM 201 & Molecular ion fragments to give an acyl cation m/z 86 + m/z 57 Mass Spectrometry CH 2 CH 3 CH 3 CH 2 CCH 2 CH 3 +O CH 3 CH 2 C O +

Dr. Wolf's CHM 201 & End of Chapter 17