Chapter 3 ketone


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Chapter 3 ketone

  1. 1. Chapter 3: KETONE Norfazrin Mohd Hanif Faculty of Applied Science UiTM Negeri Sembilan
  2. 2. SUBTOPICS Nomenclature – common and IUPAC names for ketones Physical properties of ketones : Boiling points and solubility Preparation of ketone Oxidation of 2 °Alcohol Friedel – Crafts Acylation Reactions of aldehyde Reduction To 2 ° Alcohol Nucleophilic Addition Reaction with Grignard Reagent Iodoform Reaction
  3. 3. Ketones • Functional group: carbonyl group C O  Ketone: the carbon atom in the carbonyl group is bonded to two hydrocarbon groups. O R C R' ketone R, R' = substituents
  4. 4. IUPAC NAME • The IUPAC name of a ketone is derived from the name of the alkane corresponding to the longest carbon chain that contains the ketone-carbonyl group. • The parent name is formed by changing the ending of the alkane to -one. propane propanone one –e
  5. 5. IUPAC NAME  If the carbon chain is longer than 4 carbons, it’s numbered so that the carbonyl carbon has the smallest number possible, and this number is prefixed to the name of the ketone. This end of the chain is closest to the C=O. Begin numbering here.
  6. 6. IUPAC NAME 1 2 3 4 5 6 IUPAC name: 3-hexanone New IUPAC name: hexan-3-one
  7. 7. Common Names of Ketones :O: R C • R' alkyl alkyl ketone 7 Most common names for ketones are formed by naming both alkyl groups on the carbonyl carbon, arranging them alphabetically, and adding the word “ketone”.
  8. 8. NOMENCLATURE OF CYCLIC KETONES AND AROMATIC COMPOUNDS • • The parent name is formed by changing the cycloalkane to -one. Carbonyl carbon is designated C1. –e ending of the O O 612 5 3 4 CH3 cyclohexanone 4-methylcyclohexanone  Aromatic compound: - phenyl is used as part of the name. O O C CH3 C phenylethanone diphenylmethanone
  9. 9. NOMENCLATURE OF KETONES CONTAINING TWO DIFFERENT FUNCTIONAL GROUPS  A ketone group can also be named as a substituent on a molecule with another functional group as its root.  The ketone carbonyl is designated by the prefix oxo-.  Carboxylic acids frequently contain ketone group named as substituents. CH3CH2 C CH2 C H 5 4 3 2 1 3-oxopentanal O O O O CH3 C CH2 C OH 4 3 2 1 3-oxobutanoic acid
  10. 10. Physical Properties : Boiling point • Oxygen is more electronegative than carbon (3.5 vs 2.5) and, therefore, a C=O group is polar O Polarity of a carbonyl group O: : C C + C : : + - O: – More important contributing structure •Ketones are polar due to this C=O bond and therefore have stronger intermolecular forces than hydrocarbons making their boiling points higher. 10
  11. 11. Physical Properties : solubility   The reason for the solubility is that they can form hydrogen bond with water molecules.  11 The small ketones are freely soluble in water but solubility falls with chain length. One of the slightly positive hydrogen atoms in a water molecule can be sufficiently attracted to one of the lone pairs on the oxygen atom of a ketone for a hydrogen bond to be formed. 11
  12. 12. Physical Properties : solubility • Ketones can form hydrogen bonds with water and therefore low molecular weight ketones have appreciable water solubility 12 12
  14. 14. 2.1 Oxidation of 2 °Alcohol • Ketones can be made from 2o alcohols by oxidation * [O] = • Examples 14
  15. 15. 2.2 Friedel – Crafts Acylation • Aromatic ketones can be made by Friedel-Crafts Acylation • Examples 15
  17. 17. REACTIONS OF KETONES  Reduction  Addition  Condensation  Iodoform reaction  Reaction with Grignard reagent
  18. 18. 3.1 Reduction to Secondary Alcohols  Ketones can be reduced to alcohols using: a) lithium aluminium hydride (LiAlH4) b) sodium borohydride (NaBH4) c) catalytic hydrogenation O R O- C R' LiAlH4 or NaBH4 or H2, Ni R ketone C R' OH + H R C R' H H + o H = diluted acid such as H2SO4 2 alcohol  Example: O- O CH3 C CH3 propanone H2/Ni CH3 C H OH CH3 H+ CH3 C CH3 H 2-propanol
  19. 19. 3.2a Nucleophilic addition of hydrogen cyanide * Cyanohydrin may be formed using liquid HCN with a catalytic amount of sodium cyanide or potassium cyanide. O R C R' OH HCN ketone R C R' CN cyanohydrin example O CH3 C CH3 propanone OH HCN CH3 C CH3 CN 2-hydroxy-2-methylpropanenitrile
  20. 20. 3.2a Nucleophilic addition of hydrogen cyanide  Cyanohydrin can be hydrolysed to give α-hydroxyacids.  The nitrile (-CN) group is converted to the –COOH group by reflux the cyanohydrin with dilute sulphuric acid (H2O/H+) or concentrated HCl. O R C R' OH HCN ketone R ' OH C CN H2O/H+ R R' C COOH NH4+ R cyanohydrin a-hydroxyacid example O CH3 C CH2CH3 propan-2-one OH HCN OH + CH3 C CN CH2CH3 H2O/H CH3 C COOH CH2CH3 NH4+
  21. 21. 3.2b Nucleophilic addition of sodium bisulphite (NaHSO3)  When shaken with an aqueous of sodium bisulphite, most aldehydes and ketones formed carbonyl bisulphite (a colourless crystal).  The reaction takes place more readily with aldehydes than with ketones.  The nucleophile is the hydrogensulphite ion, HSO3 Example: O NaHSO3 OH C CH3 C CH3 OSO2- Na+ Bisulphite salts
  22. 22. 3.3 Condensation with hydrazines, hydroxlamine, phenylhydrazine and 2,4-dinitrophenylhydrazine  Aldehydes and ketones condense with ammonia derivatives such as hydroxylamine and substituted hydrazines to give imine derivatives. i) Reaction with hydrazine: Hydrazines derivatives reacts with aldehydes or ketones to form hydrazones. O R C R' H2N-NH2 aldehyde or ketone + H hydrazine N NH2 R C R' H2O hydrazone derivative Example: O H3C C CH3 propanone H2N-NH2 + H NNH2 H3C C CH3 hydrazine propanone hydrazone H2O
  23. 23. 3.3 Condensation with hydrazines, hydroxlamine, phenylhydrazine and 2,4-dinitrophenylhydrazine ii) Reaction with hydroxylamine: Hydroxylamine reacts with ketones and aldehydes to form oximes. O R C R' aldehyde or ketone H2N-OH + H hydroxylamine N OH H2O R C R' oxime Example: H2N-OH O phenyl-2-propanone hydroxylamine H+ N H2O OH phenyl-2-propanone oxime
  24. 24. 3.3 Condensation with hydrazines, hydroxlamine, phenylhydrazine and 2,4-dinitrophenylhydrazine iii) Reaction with phenylhydrazine: O H R C R' aldehyde or ketone N NH Ph H + H phenylhydrazine N NH-Ph R C R' H2O phenylhydrazone Example: O H N NH Ph H+ H penta-2-one phenylhydrazine N-NH-Ph H2O penta-2-one phenylhydrazone
  25. 25. 3.3 Condensation with hydrazines, hydroxlamine, phenylhydrazine and 2,4-dinitrophenylhydrazine iv) Reaction with 2,4-dinitrophenylhydrazine: NO2 R R' C O aldehyde or ketone H2N N NO2 R room NO2 temperature H R' C NO2 N N H2O H 2,4-dinitrophenylhydrazine 2,4-dinitrophenylhydrazone (yellow-orange precipitate) Example: O CH3 C CH2CH3 NO2 H2N N H butan-2-one NO2 room temperature 2,4-dinitrophenylhydrazine CH3 CH3CH2 C NO2 N N NO2 H butan-2-one 2,4-dinitrophenylhydrazone H2O
  26. 26. 3.4 Reaction with Grignard Reagent  A Grignard reagent (a strong nucleophile resembling a carbanion, R:- attacks the electrophilic carbonyl carbon atom to give an alkoxide intermediate.  Subsequent protonation gives an alcohol. CH3 H3C CH3CH2 MgBr ethylmagnesium bromide C O CH3CH2 C O- +MgBr acetone CH3 H3C alkoxide H3O+ CH3 CH3CH2 C OH CH3 2-methyl-2-butanol
  27. 27. 3.5 Haloform Reaction IODOFORM TEST - Reagent: solution of I2 in an alkaline medium such as NaOH or KOH. - Iodoform test is useful for the methyl ketone group (CH3C=O) in ketones. - when ketones containing methyl ketone group is warmed with iodoform reagent, a yellow precipitate of triiodomethane (iodoform) is formed. The overall reaction is O R C CH3 O 3I2 NaOH heat R C O- Na+ salts CHI3 3HI iodoform (yellow precipitate)
  28. 28. Tests to Distinguish Aldehydes and Ketones, and Aliphatic Aldehydes and Aromatic Aldehydes TESTS ALDEHYDES KETONES Tollens’ Test / silver mirror test Reagent and condition: - ammoniacal silver nitrate solution ([Ag(NH3)2]+) Observation: Formation of silver mirror Observation: Silver mirror did not formed * Ketones do not react with Tollens’ reagent Fehling’s test / Benedict’s test Reagent and condition: -Solution of Cu2+ (aq) ions in an alkaline solution of sodium potassium tartate. Observation; Blue colour of the Fehling’s solution dissappears and brick-red precipitate is obtained * Except benzaldehyde Observation: Blue colour remains. * Ketones do not react with Fehling’s/Benedict’s reagent Observation: Formation of magenta-pink colour (simple aldehydes) * Except benzaldehyde and a few aromatic aldehydes) Observation: Ketones (except propanone) do not react with Schiff’s reagent. *Can be used to distinguish between: i) Aldehydes and ketones ii) Aliphatic aldehydes and benzaldehyde Schiff’s test Reagent and condition: - Schiff’s reagent
  29. 29. Thank you!
  30. 30. CHM 301 Chapter 1 : Alcohol
  31. 31. Question a. A compound , J (C4H10O), has three isomers K,L and M. K is 2-methyl-1-propanol and L is 2methyl-2-propanol. i) Draw the structural formulae of K and L ii) Describe how you would prepare K using Grignard reagent iii) Draw structural formula of M and name it. b. Compare and provide justification for the acidity of phenol, ethanol and water.