18 Aldehydes and Ketones Testosterone 18.1 THE CARBONYL GROUP H - - PowerPoint PPT Presentation

Aldehydes and Ketones

18

Testosterone

18.1 THE CARBONYL GROUP

C O H H Formaldehyde, the carbonyl group, is shown in red. C O H H formaldehyde 116.5o 121.7o C O CH3 CH3 acetone 117.2o 121.4o C O H H 1 C O H H 2 CH3—CH2—CH=CH2 CH3—CH2—CH=O 1-butene (0.2 D) propanal (2.5 D)

Figure 18.1 Structure of Formaldehyde

Te carbonyl carbon and oxygen atoms of formaldehyde are sp2-hybridized. Te H—C—H bond angle is close to 1200. Te two sets of lone pair electrons are in sp2 hybrid orbitals that are in the same plane as the hydrogen atoms.

Formaldehyde C H H O C H H O C H H O nodal plane destructive interaction C H O constructive interaction π π∗

ENERGY

Bonding and Antibonding Molecular Orbitals of Formaldehyde

18.1 THE CARBONYL GROUP

Carbonyl Compounds

C O R H general formulas for an aldehyde C O H R C O R R general formulas for a ketone C O R R

• r

18.1 THE CARBONYL GROUP

Naturally Occurring Aldehydes and Ketones

Figure 18.2 Structures of Naturally Occurring Aldehydes and Ketones

CH3 CH3 C O CH3 CH3 CH3 H retinal CH3 CH3 C O CH3 α-ionone CH3 norethindrone, an oral contraceptive C H CH3 O H H C H OH CH methandrostenolone, an anabolic steroid C CH3 CH3 O H H CH3 H OH

C O H H formaldehyde C O CH3 CH3 acetone C O CH3 H acetaldehyde benzaldehyde C O H C O CH3 acetophenone C O benzophenone

18.2 NOMENCLATURE OF ALDEHYDES AND KETONES

Common Names of Aldehydes

1. Name the longest continuous carbon chain that contains the carbonyl carbon atom as the par- ent chain. Replace the final -e of the parent hydrocarbon by the ending -al.

• 2. Number the parent chain to make the carbonyl carbon atom C-1. Te number 1 is not

required because the position of the carbonyl carbon atom must be at the end of the chain. Determine the name of each substituent and the number of the carbon atom to which it is

• attached. Add this information to the parent name as a prefix.
• 3. Te aldehyde functional group has a higher priority than alkyl, halogen, hydroxyl, and alkoxy
• groups. If any of these groups is present, indicate their names and positions as prefixes to the

name of the parent aldehyde. C CH3 C H C CH3 H

This is 2,3-dimethylbutanal, not 2,3-dimethyl-1-butanal.

CH3

4 3 2 1

H O C OH C H C CH3 H 3-hydroxy-2-methylbutanal CH3

4 3 2 1

H O

18.2 NOMENCLATURE OF ALDEHYDES AND KETONES

IUPAC Names of Aldehydes

• 4. Te aldehyde functional group has a higher priority than double or triple bonds. When the

parent chain contains a double or triple bond, replace the final -e of the name of the parent alkene or alkyne with the suffix -al. Indicate the position of the multiple bond with a prefix. CH C C C 4-methyl-2-pentynal

4 3 1

H O

2

CH3 CH3

5

• 5. If an aldehyde or ketone contains other groups with a higher priority, such as carboxylic acids,

give the carbonyl group the prefix -oxo. Use a number to indicate the position of the oxo

• group. Te priority order is carboxylic acid > aldehyde > ketone.

C O C H C CH3 2-methyl-3-oxobutanal CH3

4 3 2 1

H O

• 6. If an aldehyde group is attached to a ring, use the suffix -carbaldehyde.

C O H cyclohexanecarbaldehyde CHO Br cis-2-bromocyclopentanecarbaldehyde

18.2 NOMENCLATURE OF ALDEHYDES AND KETONES

IUPAC Names of Aldehydes

18.3 PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES

C O CH3 CH3 2-propanone (2.9 D) (acetone) C O CH3 CH3

• r

δ+ δ

Figure 18.3 Electron Density Map of Acetone

(a) Te carbonyl bond is highly polar. Te oxygen atom, shown in red, has a large, partial negative charge; the carbonyl carbon has a partial positive charge, as do the two carbons that are α to the carbonyl group. (b) Electrostatic potential map. Regions shown in red have a partial negative charge; regions shown in blue have a partial positive charge.

(a) (b)

18.3 PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES

Boiling Points of Aldehydes and Ketones

Table 18.1

Effect of Functional Groups on Boiling Points Compound Formula Molecular Weight Boiling Point (oC) ethane CH3CH3 30

• 89

methanol CH3OH 32 64.6 methanal CH3CHO 30

• 21

propane CH3CH2CH3 44

• 42

ethanol CH3CH2OH 46 78.3 ethanal CH3CH2CHO 44 20 butane CH3CH2CH2CH3 58

• 1

1-propanol CH3CH2CH2OH 60 97.1 propanal CH3CH2CHO 58 48.8 methylpropane CH3CH(CH3)2 58

• 12

2-propanol CH3CH(OH)CH3 60 82.5 propanone CH3COCH3 58 56.1

18.3 PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES

Solubility of Aldehydes and Ketones in Water

C O CH3 CH3 H O H H O H The lone pair electrons of the carbonyl group act as hydrogen bond acceptors.

Acetone and 2-Butanone as Solvents

C O CH3 CH3 H O R H O R The lone pair electrons of the carbonyl group act as hydrogen bond acceptors. Hence, acetone is an excellent solvent for alcohols.

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS

Oxidation of Aldehydes

R C H OH H R C H O reduction

• xidation

R C OH O R C H O R C O O + 2 Ag(NH3)2+ + 3 OH- + 2 Ag(s) + 4 NH3 + 2H2O + Ag(s) Ag(NH3)2+ C CHO CH3 H C CO2 CH3 H C CH2CH3 O Ag(NH3)2+ no oxidation product R C H O R C O O + 2 Cu2+ + 5 OH- + Cu2O(s) + 3 H2O blue solution red precipitate + Cu2O Cu2+ C CH3 O Cu2+ no oxidation product C CHO H H C CO2 H H

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS

Reduction of Aldehydes and Ketones to Alcohols

NaBH4 C CHO CH3 H C CH2OH CH3 H C CH2CH3 O

• 1. LiAlH4

ethanol

• 2. H3O+

C CH2CH3 OH H

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS

Reduction of a Carbonyl Group to a Methylene Group O Zn(Hg) / HCl H H O H2NNH2/ KOH H H

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS

NAD-Dependent Oxidation of Ethanol

CH3CH2OH + NAD+ LADH CH3CHO + NADH + H+ N H R C NH2 O NAD+, re-face N HR R C NH2 O HS Enz-B CH3 C HS O H HR + NADH C O CH3 H N H R C NH2 O NAD+, re-face N D R C NH2 O H Enz-B H C D O H CH3 + NADD C O H CH3

LADH

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW

Oxidation of Alcohols

CH2CH2CH2OH PCC CH2CH2 C H O

Friedel-Crafts Acylation

CH3 OCH3 + CH3CH2CH2 C Cl O CH3 OCH3 C O CH2CH2CH3 AlC3 HO2C CH3 CH3 HF CH3 CH3 O CH3 AlCl3 CO / HCl CH3 CHO

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW

Ozonolysis of Alkenes

H3C CH3 CH2 H3C CH3

• 1. O3
• 2. Zn/ H+

O Oxidative Cleavage of Vicinal Diols C OH C OH CH2CH3 CH3 H 2-methyl-1-phenyl-1,2-butanediol + HIO4 C O C O CH2CH3 CH3 H OH OH HIO4 O O H H benzaldehyde 2-butanone cis-1,2-cyclohexanediol 6-oxohexanal OsO4

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW

Hydration of Alkynes

C C C C H H Hg2+ OH H H2SO4 (aq) C CH3 O CH3CH2 C C CH3 Hg2+ H2SO4 (aq) CH3CH2 C CH2CH3 O CH3CH2CH2 C CH3 O + approximately equal amounts + alkenylborane C C C C H B H B C C H B H2O2 NaOH C C H O H C C H H O enol C C H CH3 CH3 CH3 BH3 / THF B CH3 CH3 CH3 CH3 CH3 CH3 H disiamylborane (CH3)2CH C C CH3

• 1. disiamylborane
• 2. H2O2 / NAOH

CH3CH2 C CH2CH3 O (CH3)2CHCH2 C CH3 O + 93 % 7 %

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW

Reduction of Acid Chlorides

R C Cl O acid chloride R C OH O carboxylic acid + Cl S Cl O CH3O Cl O H2 / Pd-C

N

CH3O H O Li+[AlH(O(CH3)3] + 3 H2 LiAlH4 + 3 (CH3)3COH

• 1. Li+[AlH(O(CH3)3]
• 2. H3O+

CH3(CH2)5CH2 C Cl O

• ctanoyl chloride

CH3(CH2)5CH2 C H O

• ctanal
• 1. LiAlH4
• 2. H3O+

CH3(CH2)5CH2 C Cl O

• ctanoyl chloride

CH3(CH2)5CH2 C H OH 1-octanol H

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW

Reduction of Esters

• 1. DIBAL
• 2. H3O+

CH3(CH2)10CH2 C OCH3 O methyl hexadecanoate CH3(CH2)10CH2 C H O hexadecanal R C OCH3 O R C OCH3 O + R'2 Al H AlR'2 H R C OCH3 O AlR'2 H + H3O+ R C OCH3 O H H a hemiacetal R C H O + CH3OH

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW

Reactions of Acid Derivatives with Organometallic Reagents

C OH O LiOH C O O Li CH3Li C O O CH3 Li Li C O O CH3 Li Li H3O+ C OH OH CH3

• H2O

C O CH3 C OH O C O O Li Li 2 C6H5Li C O H3O+ C O O Li Li C Cl O +[(CH3)2C CH]2CuLi C CH O CH(CH3)2

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW

Synthesis of Carbonyl Compounds From Nitriles

CH2 C N H Al(OCH2CH3)3 Li H3O+ CH2 C NH H imine CH2 C NH H H3O+ CH2 C O H + NH3 CH2 C N CH3MgBr CH2 C N CH3 MgBr H3O+ CH2 C N CH3 MgBr CH2 C N CH3 H CH2 C N CH3 H H2O CH2 C O CH3 CH2 C N LiAlH(OCH2CH3)3 CH2 C N H Al(OCH2CH3)3 Li

18.7 SPECTROSCOPY OF ALDEHYDES AND KETONES

Infrared Spectroscopy

Figure 18.4 IR Spectrum of 3-buten-2-one

Te carbonyl stretching frequency occurs at 1670 cm-1.

Transmittance Wavenumber (cm-1)

3-buten-2-one C=O stretch 1670 cm-1 CH C O CH3 CH2

18.7 SPECTROSCOPY OF ALDEHYDES AND KETONES

Proton NMR Spectroscopy

Figure 18.5 Proton NMR Spectrum of 2-Butanone

Chemical shift, ppm (δ) TMS 3H triplet 3H singlet 2H quartet CH2 C O CH3 CH3 2-butanone

18.7 SPECTROSCOPY OF ALDEHYDES AND KETONES

C-13 NMR Spectroscopy

Figure 18.6 C-13 NMR Spectrum of 2-Butanone

Chemical shift, δ (ppm) C1 C2 C3 19 δ =209 37 20 40 60 80 CH2 C O CH3 CH3 2-butanone 100 200 C4 6