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

18 Aldehydes and Ketones Testosterone

18.1 THE CARBONYL GROUP H C O H Formaldehyde, the carbonyl group, is shown in red. 121.7 o 121.4 o H CH 3 116.5 o 117.2 o C O C O H CH 3 acetone formaldehyde H H C O C O H H 2 1 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 sp 2 -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. nodal plane H H O O C C π∗ H H E NERGY Formaldehyde destructive interaction H H O O C π C H constructive interaction Bonding and Antibonding Molecular Orbitals of Formaldehyde

18.1 THE CARBONYL GROUP Carbonyl Compounds H O C O R C H R general formulas for an aldehyde O R or C O R C R R general formulas for a ketone

18.1 THE CARBONYL GROUP Naturally Occurring Aldehydes and Ketones Figure 18.2 Structures of Naturally Occurring Aldehydes and Ketones CH 3 CH 3 H CH 3 CH 3 CH 3 CH 3 CH 3 C C O O CH 3 CH 3 retinal α -ionone OH OH CH 3 CH 3 C CH CH 3 H H CH 3 H H H H H C C O O norethindrone, an oral contraceptive methandrostenolone, an anabolic steroid

18.2 NOMENCLATURE OF ALDEHYDES AND KETONES Common Names of Aldehydes H H CH 3 C O C O C O H CH 3 CH 3 formaldehyde acetaldehyde acetone O O O C H C CH 3 C benzaldehyde acetophenone benzophenone

18.2 NOMENCLATURE OF ALDEHYDES AND KETONES IUPAC 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. CH 3 H O 4 3 2 This is 2,3-dimethylbutanal, CH 3 C C C H not 2,3-dimethyl-1-butanal. 1 H CH 3 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. OH H O 4 3 2 CH 3 C C C H 1 H CH 3 3-hydroxy-2-methylbutanal

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 3 O CH 3 CH C C C H 3 1 2 5 4 4-methyl-2-pentynal 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. O H O CH 3 C C C H 3 2 1 4 CH 3 2-methyl-3-oxobutanal 6. If an aldehyde group is attached to a ring, use the suffix - carbaldehyde . H CHO C O Br cyclohexanecarbaldehyde cis -2-bromocyclopentanecarbaldehyde

18.3 PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES 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) CH 3 CH 3 or C O C O δ + δ CH 3 CH 3 2-propanone (2.9 D) (acetone)

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 ( o C) ethane CH 3 CH 3 30 -89 methanol CH 3 OH 32 64.6 methanal CH 3 CHO 30 -21 propane CH 3 CH2CH3 44 -42 ethanol CH 3 CH 2 OH 46 78.3 ethanal CH 3 CH 2 CHO 44 20 butane CH 3 CH2CH2CH 3 58 -1 1-propanol CH 3 CH2CH2OH 60 97.1 propanal CH 3 CH2CHO 58 48.8 methylpropane CH 3 CH(CH3)2 58 -12 2-propanol CH 3 CH(OH)CH3 60 82.5 propanone CH 3 COCH3 58 56.1

18.3 PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES Solubility of Aldehydes and Ketones in Water H H H O O H O C CH 3 CH 3 The lone pair electrons of the carbonyl group act as hydrogen bond acceptors. Acetone and 2-Butanone as Solvents R R H O O H O C CH 3 CH 3 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 OH O O reduction oxidation R C H R C OH R C H H O O + 2 Ag(NH 3 ) 2+ + 3 OH - R O + 2 Ag(s) + 4 NH 3 + 2H 2 O R C H C CH 3 CH 3 Ag(NH 3 ) 2+ + Ag(s) C CHO C CO 2 H H O Ag(NH 3 ) 2+ no oxidation product C CH 2 CH 3 O O + 2 Cu 2+ + 5 OH - R C O + Cu 2 O(s) + 3 H 2 O R C H blue solution red precipitate H H Cu 2+ + Cu 2 O C CO 2 C CHO H H O Cu 2+ no oxidation product C CH 3

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS Reduction of Aldehydes and Ketones to Alcohols CH 3 CH 3 NaBH 4 C CHO C CH 2 OH ethanol H H O OH 1. LiAlH 4 C CH 2 CH 3 C CH 2 CH 3 2. H 3 O+ H

18.4 OXIDATION-REDUCTION REACTIONS OF CARBONYL COMPOUNDS Reduction of a Carbonyl Group to a Methylene Group H O Zn(Hg) / HCl H O H H H 2 NNH 2 / KOH

18.4 OXIDATION - REDUCTION REACTIONS OF CARBONYL COMPOUNDS NAD-Dependent Oxidation of Ethanol LADH CH 3 CH 2 OH + NAD + CH 3 CHO + NADH + H + Enz-B O H O H R H S H O C C O NH 2 NH 2 + C CH 3 C H S CH 3 H N N H R R R NAD + , re -face NADH Enz-B O H O D H H O C C O NH 2 NH 2 + LADH C H C D H CH 3 N N CH 3 R R NAD + , re -face NADD

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW Oxidation of Alcohols O CH 2 CH 2 CH 2 OH PCC CH 2 CH 2 C H Friedel-Crafts Acylation CH 3 CH 3 O O C CH 2 CH 2 CH 3 AlC 3 + CH 3 CH 2 CH 2 C Cl OCH 3 OCH 3 CH 3 CH 3 HF CH 3 HO 2 C CH 3 O CH 3 CH 3 CO / HCl AlCl 3 CHO

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW Ozonolysis of Alkenes H 3 C CH 3 H 3 C CH 3 1. O 3 2. Zn/ H + O CH 2 Oxidative Cleavage of Vicinal Diols OH OH HIO 4 O O C C CH 2 CH 3 + C C CH 2 CH 3 H CH 3 H CH 3 2-methyl-1-phenyl-1,2-butanediol benzaldehyde 2-butanone H OH HIO 4 O OsO 4 O OH H cis-1,2-cyclohexanediol 6-oxohexanal

18.5 SYNTHESIS OF CARBONYL COMPOUNDS: A REVIEW Hydration of Alkynes OH H O Hg 2+ C C H C C H C CH 3 H 2 SO 4 (aq) O Hg 2+ CH 3 CH 2 C C CH 3 CH 3 CH 2 C CH 2 CH 3 approximately H 2 SO 4 (aq) + equal amounts O CH 3 CH 2 CH 2 C CH 3 H B + H C C C C B alkenylborane H H B H H O O H 2 O 2 C C C C C C NaOH H enol CH 3 CH 3 CH 3 H BH 3 / THF CH 3 CH 3 C C B CH 3 CH 3 H CH 3 CH 3 disiamylborane O O 1. disiamylborane + (CH 3 ) 2 CH C C CH 3 (CH 3 ) 2 CHCH 2 C CH 3 CH 3 CH 2 C CH 2 CH 3 2. H 2 O 2 / NAOH 93 % 7 %

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW Reduction of Acid Chlorides O O O + Cl R C OH S Cl R C Cl carboxylic acid acid chloride O O H 2 / Pd-C Cl H CH 3 O CH 3 O N Li + [AlH(O(CH 3 ) 3 ] + 3 H 2 LiAlH 4 + 3 (CH 3 ) 3 COH O O 1. Li + [AlH(O(CH 3 ) 3 ] CH 3 (CH 2 ) 5 CH 2 C Cl CH 3 (CH 2 ) 5 CH 2 C H 2. H 3 O + octanoyl chloride octanal O OH 1. LiAlH 4 CH 3 (CH 2 ) 5 CH 2 C Cl CH 3 (CH 2 ) 5 CH 2 C H 2. H 3 O + H octanoyl chloride 1-octanol

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW Reduction of Esters O O 1. DIBAL CH 3 (CH 2 ) 10 CH 2 C OCH 3 CH 3 (CH 2 ) 10 CH 2 C H 2. H 3 O + methyl hexadecanoate hexadecanal O O AlR' 2 R C OCH 3 + R' 2 Al H R C OCH 3 H O H O O AlR' 2 + H 3 O + + CH 3 OH R C OCH 3 R C H R C OCH 3 H H a hemiacetal

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW Reactions of Acid Derivatives with Organometallic Reagents O Li O O CH 3 Li LiOH Li Li C O C OH C O CH 3 O Li OH O H 3 O + - H 2 O Li C O C OH C CH 3 CH 3 CH 3 O Li O 2 C 6 H 5 Li Li C O C OH O Li O H 3 O + Li C O C O O +[(CH 3 ) 2 C C Cl CH] 2 CuLi C CH CH(CH 3 ) 2

18.6 SYNTHESIS OF CARBONYL COMPOUNDS: A PREVIEW Synthesis of Carbonyl Compounds From Nitriles CH 2 C N LiAlH(OCH 2 CH 3 ) 3 Al(OCH 2 CH 3 ) 3 Li N CH 2 C H Al(OCH 2 CH 3 ) 3 Li N NH H 3 O + C C CH 2 CH 2 H H imine NH O H 3 O + + NH 3 C CH 2 C CH 2 H H MgBr N CH 3 MgBr CH 2 C N CH 2 C CH 3 MgBr H N N H 3 O + C CH 2 CH 2 C CH 3 CH 3 H N O H 2 O CH 2 C C CH 2 CH 3 CH 3

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 O CH 2 CH C CH 3 C=O stretch 1670 cm -1 3-buten-2-one Wavenumber (cm -1 )

18.7 SPECTROSCOPY OF ALDEHYDES AND KETONES Proton NMR Spectroscopy Figure 18.5 Proton NMR Spectrum of 2-Butanone O CH 3 CH 2 C CH 3 2-butanone 3H singlet 3H triplet 2H quartet TMS Chemical shift, ppm ( δ )