Chapter 17 Aldehydes and Ketones Nucleophilic Addition to the Carbonyl Group

1. Chapter 17Aldehydes and KetonesNucleophilic 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 with -al.

4. O O H H O O HCCHCH IUPAC Nomenclature of Aldehydes 4,4-dimethylpentanal 5-hexenal or hex-5-enal 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 with -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 or Hexan-3-one 4-methyl-2-pentanone or 4-methylpentan-2-one 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 Boiling Pointsthan 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%)