2. 1. Structure
The carbonyl group is a double bond between oxygen and
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
|| propanal 58 49 oC
|| propanone 58 56 oC
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.
8. 1. Solubility in water—general guidelines
Molecules with polar groups tend to be more soluble in
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
9. 2. Nomenclature
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
10. 2. Nomenclature
The simplest aldehydes
Draw structures for
trans-2-hexenal (component of olive oil)
12. 2. Nomenclature
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.
13. 2. Nomenclature
The simplest ketones need no number for the carbonyl.
Draw structures for the following compounds.
15. 3. Important aldehydes and ketones
What is the relationship between embalming fluid and
What is the I.U.P.A.C. name of the following component
16. 3. Important aldehydes and ketones
What is the I.U.P.A.C. name for cinnamaldehyde?
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.
17. 3. Important aldehydes and ketones
Aldehydes in perfumery
heptanal: naturally occuring in clary sage and possessing a herbal
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
lauryl aldehyde (12 carbons): evocative of lilacs or violets
22. 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
23. 4. Reactions--oxidation
+ Ag(NH3)2+ + Ago
If an aldehyde is present, a “silver mirror”
forms on the inside of the glass
If a ketone is present, there is no
reaction because it won’t undergo
24. 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.
27. 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.
reducing sugar + Cu+2 oxidized sugar + Cu2O
29. 4. Reactions—blast from the past
Can you remember Chapter 12?
Preparation of alcohols by hydrogenation of aldehydes and
ketones (slide 19)
30. 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.
32. 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
34. 4. Reactions--addition
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.
36. 4. Reactions--addition
Ketones undergo analogous addition reactions with
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
40. 4. Reactions
Monosaccharide addition reactions
The cyclic form is more stable than the linear form and no
further oxidation takes place in this case.
41. 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.
43. 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.
44. 4. Reactions: aldol condensation
Write an equation for the aldol condensation of two
molecules of propanal.
Hinweis der Redaktion
Note that the alcohol has a dramatically higher boiling point because of its ability to hydrogen-bond with itself. Although the ketone on this slide has a higher boiling point than the aldehyde, this isn’t consistent. Aldehydes and ketones of the same molecular weight will always have similar boiling points, but it’s not possible to predict whether the aldehyde or the ketone will have the higher boiling point.Aldehydes and ketones can’t hydrogen bond with themselves because they lack a hydrogen bonded to the double-bonded oxygen. This is why they have lower boiling points than alcohols. Ethers are less polar than aldehydes and ketones because the oxygen atom is more “hidden” between two alkyl chains. Hence, their boiling points are much lower than aldehydes and ketones and only slightly higher than boiling points for comparable alkanes.
There is one-way hydrogen bonding between aldehydes and ketones, and water. A partially positive hydrogen from water can be attracted to an unshared pair of electrons on a carbonyl oxygen. But aldehydes and ketones have no hydrogens to be attracted to unshared pairs on oxygen in water.
Propanone: This is a ketone, as indicated by the –one ending. There is only one carbon that is not an end carbon, so that is the only carbon that can have the carbonyl and the compound still be a ketone.Butanone: There are two non-end carbons on the four-carbon chain, but they are both equivalent. If we were to move the carbonyl to the other interior carbon, it might be tempting to number it 3-butanone, but that would be incorrect because numbering from the other end would take us back to having the carbonyl on the second carbon. Therefore, there is really only one position for the carbonyl and butanone needs no number.
Formalin is a solution of methanal (formaldehyde). Methanol is toxic and can cause blindness or death when as little as 4 mL is ingested. When we digest foods, they are “burned” to provide calories. This is actually the reaction of sugars produced from food with oxygen to produce carbon dioxide and water.When methanol is ingested and oxidized (burned), it forms formaldehyde and then formic acid before finally forming carbon dioxide. So, ingesting methanol causes your body to embalm itself, in a way!3,7-dimethyl-2,6-octadienal
A tertiary alcohol has three alkyl groups attached to the carbinol carbon. Oxidation can only take place if the single carbon-oxygen bond in an alcohol can be replaced by a double carbon-oxygen bond; THIS can only take place if there is a hydrogen on the carbinol carbon to be lost when the oxygen forms an additional bond to the carbon. Since tertiary alcohols don’t have this hydrogen, they can’t be oxidized to carbonyl compounds.
For the same reason tertiary alcohols can’t be oxidized, ketones can’t be oxidized. Oxidation required the formation of an additional C-O bond at the carbonyl group carbon. But this would require that the same carbon lose a hydrogen. There’s no hydrogen to lose, so there’s no oxidation.