Chapter 17 Aldehydes and Ketones. Nucleophilic Addition to the Carbonyl Group

1. Chapter 17Aldehydes and Ketones.Nucleophilic Additionto theCarbonyl Group

2. 17.1Nomenclature

3. O O H H O O HCCHCH IUPAC Nomenclature of Aldehydes Base the name on the chain that contains the carbonyl group and replace the -e ending of the hydrocarbon by -al.

4. O O H H O O HCCHCH IUPAC Nomenclature of Aldehydes 4,4-dimethylpentanal 5-hexenal 2-phenylpropanedial(keep the -e endingbefore -dial)

5. O when named as a suffix C when named as a substituent H formyl group carbaldehyde orcarboxaldehyde IUPAC Nomenclature of Aldehydes

6. O O CH3CH2CCH2CH2CH3 CH3CHCH2CCH3 CH3 H3C O Substitutive IUPAC Nomenclature of Ketones 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.

7. O O CH3CH2CCH2CH2CH3 CH3CHCH2CCH3 CH3 H3C O Substitutive IUPAC Nomenclature of Ketones 3-hexanone 4-methyl-2-pentanone 4-methylcyclohexanone

8. O O CH3CH2CCH2CH2CH3 CH2CCH2CH3 O H2C CH CHC CH2 Functional Class IUPAC Nomenclature of Ketones List the groups attached to the carbonyl separately in alphabetical order, and add the word ketone.

9. O O CH3CH2CCH2CH2CH3 CH2CCH2CH3 O H2C CH CHC CH2 Functional Class IUPAC Nomenclature of Ketones ethylpropyl ketone benzylethyl ketone divinyl ketone

10. 17.2Structure and Bonding:The Carbonyl Group

11. Structure of Formaldehyde planar bond angles: close to 120° C=O bond distance: 122 pm

12. very polar double bond dipole moment = 2.5D dipole moment = 0.3D The Carbonyl Group O 1-butene propanal

13. O H O Carbonyl group of a ketone is morestable than that of an aldehyde Alkyl groups stabilize carbonyl groups the sameway they stabilize carbon-carbon double bonds,carbocations, and free radicals. heat of combustion 2475 kJ/mol 2442 kJ/mol

14. O H O Spread is greater foraldehydes andketones than for alkenes Heats of combustion ofC4H8 isomeric alkenes CH3CH2CH=CH2 2717 kJ/mol cis-CH3CH=CHCH3 2710 kJ/mol trans-CH3CH=CHCH3 2707 kJ/mol (CH3)2C=CH2 2700 kJ/mol 2475 kJ/mol 2442 kJ/mol

15. •• – •• O O •• •• •• C C + Resonance Description ofCarbonyl Group nucleophiles attack carbon; electrophiles attack oxygen

16. Bonding in Formaldehyde Carbon and oxygen are sp2 hybridized

17. Bonding in Formaldehyde The half-filledp orbitals oncarbon andoxygen overlapto form a  bond

18. 17.3Physical Properties

19. O OH Aldehydes and ketones have higher boilingthan alkenes, but lower boiling points than alcohols. boiling point More polar than alkenes, but cannot form intermolecular hydrogen bonds to other carbonyl groups –6°C 49°C 97°C

20. 17.4Sources of Aldehydes and Ketones

21. O Many aldehydes and ketones occur naturally 2-heptanone(component of alarm pheromone of bees)

22. Many aldehydes and ketones occur naturally O H trans-2-hexenal (alarm pheromone of myrmicine ant)

23. Many aldehydes and ketones occur naturally O H citral (from lemon grass oil)

24. Table 17.1 Synthesis of Aldehydes and Ketones from alkenes ozonolysis from alkynes hydration (via enol) from arenes Friedel-Crafts acylation from alcohols oxidation A number of reactions alreadystudied provideefficient syntheticroutes to aldehydes and ketones.

25. O O C C R H R OH 1. LiAlH4 PDC, CH2Cl2 2. H2O RCH2OH What about..? aldehydes from carboxylic acids

26. O O COH CH 1. LiAlH4 PDCCH2Cl2 2. H2O CH2OH (83%) (81%) Example benzaldehyde from benzoic acid

27. O O C C R R' R H 1. R'MgX OH PDC, CH2Cl2 2. H3O+ RCHR' What about..? ketones from aldehydes

28. O CH3CH2C(CH2)3 CH3 1. CH3(CH2)3MgX H2CrO4 OH 2. H3O+ CH3CH2CH(CH2)3 CH3 Example 3-heptanone from propanal O C CH3CH2 H (57%)