1. Aldehydes and Ketones
Chapter 13

2. 1. Structure
 The carbonyl group is a double bond between oxygen and
carbon.
 Carbonyl compounds include:
 Aldehydes: at least one hydrogen bonded to the carbonyl carbon
 Ketones: no hydrogens bonded to the carbonyl carbon.
 carboxylic acids and amides. [Tune in NEXT chapter…]

3. 1. Properties
 The carbonyl group is polar.
 Intermolecular forces in carbonyl compounds are
 stronger than in alkanes (nonpolar) or ethers (only slightly polar).
 weaker than in alcohols, which are polar and can hydrogen bond.

4. 1. Boiling points
Structure Name Molar mass Boiling point
CH3CH2CH2CH3 butane 58 -0.5 oC
CH3-O-CH2CH3 methoxyethane 60 7.0 oC
CH3CH2CH2-OH 1-propanol 60 97.2 oC
O
|| propanal 58 49 oC
CH3CH2-C-H
O
|| propanone 58 56 oC
CH3-C-CH3

5. 1. Solubility
 There is no hydrogen bonding between two carbonyl
groups.

6. 1. Solubility
 Aldehydes and ketones can hydrogen bond with water.
 Aldehydes and ketones with five or fewer carbon atoms are fairly
soluble in water.
 Large aldehydes and ketones dissolve only in nonpolar solvents.

7. 1. Solubility in water—general guidelines
 Molecules with polar groups tend to be more soluble in
water.
 Molecules that can hydrogen bond with water are more
soluble than those than cannot.
 Increasing the number of polar groups on a molecule
increases its water solubility.
 Increasing the number of possibilities for hydrogen bonding
increases solubility in water.
 Increasing the molar mass of a molecule decreases its
water solubility.

8. 2. Nomenclature
 Naming aldehydes
 The parent compound is named for the longest continuous chain
containing the carbonyl group.
 The final –e of the parent alkane is replaced with –al.
 The chain is numbered beginning at the carbonyl carbon.
 Substituents are named and numbered as usual.
 The aldehyde is always carbon 1, so no number is used for the
carbonyl group.

9. 2. Nomenclature
 The simplest aldehydes
methanal ethanal
 Draw structures for
pencast
 7,8-dibromooctanal
 trans-2-hexenal (component of olive oil)

10. 2. Nomenclature
 Name the following compounds.
pencast

11. 2. Nomenclature
 Ketones
 The rules are analogous to the rules for aldehydes.
 The –e ending of the parent alkane is changed to –one.
 The location of the carbonyl is indicated with a number. [This
number is never 1- because that would be an aldehyde!]
 The longest carbon chain is numbered to give the carbonyl the
lowest possible number.

12. 2. Nomenclature
 The simplest ketones need no number for the carbonyl.
(Why?)
propanone butanone
 Draw structures for the following compounds.
 2-fluorocyclohexanone
 3-chloro-2-pentanone
pencast

13. 2. Nomenclature
 Name the following compounds.
pencast

14. 3. Important aldehydes and ketones
 What is the relationship between embalming fluid and
methanol poisoning?
 What is the I.U.P.A.C. name of the following component of
lemongrass?
pencast

15. 3. Important aldehydes and ketones
 What is the I.U.P.A.C. name for cinnamaldehyde?
pencast
 Chanel No. 5 became famous for containing synthetic
aldehydes “in copious quantities”.*
*Perfume Shrine
Follow the link for a fun description of
properties of aldehydes and ketones.

16. 3. Important aldehydes and ketones
 Aldehydes in perfumery
 heptanal: naturally occuring in clary sage and possessing a herbal
green odour
 octanal: orange-like
 nonanal: smelling of roses
 decanal: powerfully evocative of orange rind
 citral (a more complicated 10-carbon aldehyde): odor of lemons
 undecanal: naturally present in coriander leaf oil
 unsaturated undecen-1-al
 lauryl aldehyde (12 carbons): evocative of lilacs or violets

17. 4. Reactions--oxidation
 Preparation is usually by oxidation of an alcohol.
 Aldehydes are produced from primary alcohols.
 Ketones are produced from secondary alcohols.
 Tertiary alcohols don’t undergo oxidation (no –H to lose).

18. 4. Reactions--oxidation
 Oxidation of aldehydes and ketones
 Aldehydes can be oxidized to carboxylic acids.
loss of a bond to H, gain of a bond to O
 Ketones can’t be oxidized further.
N.R. (no –H to lose)

19. 4. Reactions--oxidation
 Tollen’s test is used to distinguish between aldehydes and
ketones based on their ability to be oxidized.
 When one substance is oxidized, another must be reduced.
+ Ag(NH3)2+  + Ago
Tollen’s reagent elemental silver
 If an aldehyde is present, a “silver mirror” forms on the inside of the
glass container.
 If a ketone is present, there is no reaction because it won’t undergo
oxidation.

20. 4. Reactions--oxidation
 The same process used in Tollen’s test used to be used to
produce silvered mirrors.
 This is an article published in 1911 describing the process, if
you are interested!
 Go here to see a 2-liter flask turned into a mirror.
 For EXTRA CREDIT, explain what precautions need to be
taken when the Tollen’s test is carried out. You’ll have to
watch the video. Post your answer in the Module 4 Journal
Answers journal with the tag Tollen.

21. 4. Reactions--oxidation
 Draw the structure of the following compounds and their
oxidation products.
 2-methyl-2-propanol
 2-nonanol
pencast
 1-decanol

22. 4. Reactions--oxidation
 What reaction will pentanal undergo, if any, with Tollen’s
reagent?
+ Ag(NH3)2+  + Ago
pencast

23. 4. Reactions--oxidation
 Benedict’s test is used to distinguish between reducing
and non-reducing sugars.
 A reducing sugar can be oxidized.
 The substance reduced is Cu+2.
+ Cu+2  + Cu2O

24. 4. Reactions—blast from the past
 Can you remember Chapter 12?
 Preparation of alcohols by hydrogenation of aldehydes and ketones
(slide 19)

25. 4. Reactions--reduction
 Hydrogenation is a reduction reaction.
 More bonds to hydrogen, fewer bonds to oxygen
 Reduction of an aldehyde or ketone requires a Ni, Pt, or Pd
catalyst. [sound familiar?]
 Reduction of an aldehyde produces a primary alcohol.
 Reduction of a ketone produces a secondary alcohol.

26. 4. Reactions--reduction
 What is the product of reduction of
 1-chloropropanone?
pencast
 2-methylpropanal?

27. 4. Reactions--addition
 Take the time machine back to Chapter 11 now.
 Alkenes undergo addition reactions:
 Hydrogenation (addition of H2)
 Halogenation (addition of X2)
 Hydration (addition of H2O)
 Hydrohalogenation (addition of HX)
 General addition reaction

28. 4. Reactions--addition
 Addition of an alcohol to an aldehyde:
H+
 The product is called a hemiacetal (-OH and –OR attached
to the same carbon).
 Hemiacetals are very reactive.
 They react with an additional alcohol molecule, losing –OH and
adding another –OR.

29. 4. Reactions--addition
 The final product is an acetal (2 –OR groups attached to
one carbon).
hemiacetal acetal

30. 4. Reactions--addition
 Ketones undergo analogous addition reactions with
alcohols.
 The initial product is a reactive hemiketal (two –R groups, one –OH,
and one –OR).
 An additional –OR group is added to the hemiketal to produce a
ketal.
hemiketal ketal

31. 4. Reactions--addition

32. 4. Reactions
 Hemiacetal, acetal, hemiketal, or ketal?

33. 4. Reactions
 Monosaccharide addition reactions
alcohol
6
5 ]
4
2
1
] aldehyde
3
-glucose
D

34. 4. Reactions
 Monosaccharide addition reactions
Hemiacetal:
one –H
one –OH
5
one –OR
one -R
4 1
3 2
 The cyclic form is more stable than the linear form and no
further oxidation takes place in this case.

35. 4. Reactions: keto-enol tautomers
 Tautomers differ from each other in the placement of one
hydrogen and one double bond.
Keto form Enol form
(ketone) (alcohol + alkene)
 The two forms exist in an equilibrium mixture, mostly in the
keto form, which is more stable.

36. 4. Reactions: keto-enol tautomers
 Draw the keto and enol forms of
 propanone.
pencast
 propanal.

37. 4. Reactions: aldol condensation
 In an aldol condensation, aldehydes or ketones react to
make a larger molecule by forming a new carbon-carbon
bond between two molecules.
+
OH- or
enzyme

38. 4. Reactions: aldol condensation
 Write an equation for the aldol condensation of two
molecules of propanal.
pencast