O
Fragrant odors
 Basic building block of housing
materials
 Hormones
 Digestion
 Vision

2

Carbonyl group
› C=O
› Aldehydes
 RCH=O
 Formyl
› Ketones
 RC=OR’
3

Aldehydes
› IUPAC end in “al”
› Common end in “aldeyde”
› Carbonyl C is always #1
› Cyclic cpds
 Carbaldehyde is ending for most
4

Aldehydes
H2C
methanal
(formaldehyde)
O
H3C
ethanal
(acetaldehyde)
O
H3C
propanal
(propionaldehyde)
O
H3C
O
butanal
(n-butyraldehyde)
5

Aldehydes
H3C
3-methylbutanal
H3C
O
H2C
3-butenal
O
HO
OH
2,3-dihydropropanal
(glyceraldehyde)
O
6

Aldehydes
cyclopentanecarbaldehyde
(formylcyclopentane)
O
O
O
OH
benzenecarbaldehyde
(benzaldehyde)
2-hydroxybenzenecarbaldehyde
(salicylaldehyde)
7

Ketones
› IUPAC end in “one”
› Common end in “ketone”
› Carbonyl C is never #1, but always gets low
number preference
› Cyclic cpds
 Carbaldehyde is ending for most
8

Ketones
H3C
CH3
O
propanone
(acetone)
H3C
2-butanone
(ethyl methyl ketone)
O
CH3
H3C
O
CH3
3-pentanone
(diethyl ketone)
9

Ketones
cyclohexanone
O
O
2-methylcyclopentanone
CH3
H2C
CH3
O
3- buten-2-one
(methyl vinyl ketone)
10

Ketones
O
acetaphenone
(methyl phenyl ketone)
CH3
O
benzophenone
(diphenyl ketone)
O
dicyclopropyl ketone
11

Formaldehyde
› Simplest aldehyde
› Manufactured on large scale (8 billion lbs per
annum) from catalyzed oxidation of methanol
CH3OH CH2=O + H2
› Gas at RT (bp = -21˚C) but cannot be stored in
free state due to polymerization
› Normally 37% soln called formalin (preservative)
› Most used in making of plastics, insulation,
particle board, and plywood
12

Acetaldehyde
› Boils close to RT (bp = 20˚C)
› Made by catalyzed oxidation of ethylene
2 CH2=CH2 + O2  2 CH3CH=O
› ~1/2 is oxidized to acetic acid
› Remainder used for production of
1- butanol and others.
13

Acetone
› Simplest ketone
› Large scale production like formaldehyde
› Produced from oxidation of propene, isopropyl
alcohol, or isopropylbenzene
H3C
H3C
CH3
OOH
OH
H3C
O2
dilute H2SO4
O
+ H3C
H2O
› ~30% used directly, great solvent, H2O miscible
› Rest used to make stuff like epoxy resins
14
CH3

Quinones
› Cyclic conjugate diketones
› Simplest is 1,4-benzoquinone
› All are colored and are thus used often as
dyes
› Alizarin…used to dye the red coats of the
British Army during American Revolution
› Vitamin K is required for normal clotting of
blood
15
O
OH
OH
O
O
1,4-benzoquinone
O
alizarin
OH
CH3
CH3
OH
H3C
H3C
H3C
H3C
Vitamin K
vitamin K
16

Oxidation
› 1˚ ROH gives aldehyde
› 2˚ ROH gives ketone
› Cr reagents (PCC) are common
oxidizing
H3C
OH
agent
H2C
O
17

Friedel-Crafts Acylation
› Recall the rxn?
› Makes aromatic ketones
Cl
+
AlCl3
+
O
benzyl chloride
O
benzophenone
18
HCl

Hydration of terminal alkynes
› Gives methyl ketones
› Catalyzed by acid and mercuric ion
H3C
CH
H+, H2O
++
Hg
CH3
H3C
O
19
Many have pleasant odors
 Used in the perfume industry
 Extremely expensive to gather from
natural producers
 Chanel No. 5 (my mom’s fave perfume)
was first perfume to use synthetic
organic chemicals in 1921

20
O
CH3
O
HO
O
O
benzaldehyde
cinnamaldehyde
vanillin
21
C atom is sp2 hybridized
 Bond angles?
 C=O bond length is 1.24Å (compared to
1.43Å for C-O in ROH and ROR
 O is more EN than C

› Makes a polar bond
22
Most carbonyl reactions are nucleophilic
attacks on the carbonyl C
 C=C usually is attacked by an
electrophile
 Due to polarization, physical properties
differ from HC’s and ROH’s

› bp’s are higher than HC’s, lower than ROH’s
23

C=O is permanently polarized
› Positive part of one molecule is attracted to
negative part of another molecule
› Dipole-dipole forces, weaker than H-bonds,
stronger than LDF
24

C=O’s with low MW are soluble in water
› Can form H-bonds with water or ammonia
25
Why does the attack occur?
 If rxn occurs in hyroxylic solvent (water or
ROH), a proton is usually added to the O

26
Carbonyl cpds are weak Lewis bases
due to lone pairs on O
 Acids can catalyze the addition of weak
nucleophiles to carbonyl cpds through
protonation

27



Nucleophiles add reversibly
› Good leaving groups, CB of SA
Nucleophiles add irreversibly
› Poor LG, CB of WA
In general, ketones are less reactive than
aldehydes
› Steric…sp2 v. sp3, R v. H
› Electronic…alkyl groups are electrondonating…ketones have two
28

Alcohols are oxygen nucleophiles
› OR goes to C, and H goes to O


Because ROH’s are weak nucleophiles, acid
catalyst must be used
Product is a hemiacetal
› Contains both alcohol and ether on same C

Addition is reversible
29

Mechanism of hemiacetal formation has 3
steps
› Carbonyl O is protonated by acid catalyst
› ROH’s O then attacks carbonyl C
› Proton is then lost from resulting +O

Each step is reversible
30

Write an equation for the formation of a
hemiacetal from acetaldehyde, ethanol, and
an acid catalyst. Show each step in the rxn
mechanism.
31



Excess ROH means hemiacetals react further to
produce acetals
Hydroxyl group of hemiacetal is replaced by
an alkoxyl group.
Acetals have two ether groups on same C
32

Mechanism of acetal formation
33

Mechanism of acetal formation
34

Aldehydes that have appropriately located
hydroxyl group can exist in equilibrium with a
cyclic hemiacetal…5-hydroxypetanal
35

Aldehydes that have appropriately located
hydroxyl group can exist in equilibrium with a
cyclic hemiacetal…5-hydroxypetanal
36


Cpds with hydroxyl group 4 or 5 C’s from the
aldehyde group tend to form cyclic
hemiacetals and acetals due to lack of strain
Carbohydrates
37


Ketones also form acetals
If a glycol is used, product is cyclic
38

Summary
› Aldehyde or ketone reacts with ROH
› Hemiacetal is formed
› Further ROH makes acetal
39


Water is an oxygen nucleophile, like ROH’s
Can add reversibly
40


Aside from formaldehyde hydrate most other
hydrates cannot by isolated because they lost
water…Keq<1
One exception is trichloroacetaldehyde
(chloral)
› Forms a stable crystalline hydrate, chloral hydrate,
CCl3CH(OH)2
› Used as a sedative
41

Grignard reagents act as carbon nucleophiles
toward carbonyl cpds
› Grignard reagent adds irreversibly to the
carbonyl carbon, forming a new C-C bond
› Favorable because product (an alkoxide) is a
much weaker base than the starting carbanion
› The alkoxide can be protonated to give an ROH
42

Useful route to alcohols
› Type of carbonyl determines class of ROH
› Formaldehyde gives 1˚ ROH’s
43

Other aldehydes give 2˚ ROH’s
44

Ketones give 3˚ ROH’s
45

Other organometallic cpds like organolithium
cpds and aceylides react with carbonyl cpds
similarly to Grignard reagents
46

HCN adds reversibly to carbonyl group of
aldehydes and ketones to make cyanohydrins
› Hydroxyl and cyano group attached to same C
› Basic catalyst is needed
47

Acetone reacts as follows:
48

Cyanohydrins play important role in the
defense system of the millipede
› Two-chambered gland like the bombadier
beetle
› Benzaldehyde cyanohydrin is stored and then
converted to a mixture of benzadehyde and
hydrogen cyanide and secreted
49

Write an equation for the addition of HCN to
benzaldehyde.
50

Ammonia, amines, and other related cpds
have a lone pair on the N and thus act as a
nucleophile toward a carbonyl C
51


Aldehydes and Ketones are easily reduced to
1˚ and 2˚ alcohols, respectively
Metal hydrides used to reduce
› Irreversible nucleophilic attack
› LiAlH4 or NaBH4
52



The original product is an aluminum alkoxide
Then hydrolyzed by water and acid to give
ROH
Net result is addition of H across the C=O
1. LiAlH4
O
H
OH
2. H+, H2O
53



Aldehydes are more easily oxidized than are
ketones
Oxidation of an aldehyde gives an acid with
the same number of C’s
Oxidizing agents include KMnO4, CrO3, Ag2O
CrO3, H+
O
H3C
O
H3C
Jones reagent
OH
OH
O
Ag2O
O
54

Tollens Silver Test
› Silver-ammonia complex ion is reduced by
aldehydes but not by ketones
› If test tube is clean, a mirror forms by the metallic
Ag
› Used to “silver”
glass using
formaldehyde
(cheap)
55

Aldehydes and Ketones may exist as an
equilibrium mixture of two forms
› Keto and enol forms
› Differ in the location of a proton and a double
bond

Tautomerism (Greek…same part)
› Structural isomers
› Not resonance contributors
56

In order for an enol form to exist carbonyl C
must have an H attached to the carbon
adjacent to the carbonyl group
› Known as the -hydrogen and is attached to the
-carbon
57

Most simple aldehydes and ketones exist
primarily in the keto form
› Keto more stable
› Acetone, 99.9997% keto form

Phenols have mainly enol form
OH
O
H
H
58

Carbonyl cpds that do not have an hydrogen cannot form enols and exist only in
keto form
O
O
O
H
H
H
59

-Hydrogen is more acidic than normal H
attached to a C
› Carbonyl C carries a partial + charge, attracting bonding
electrons away from the -H…make it easy for a base to
remove the -H
› Resulting anion is stabilized by resonance…enolate anion
60



Enolate anions may act as carbon
nucleophiles
Enolate can add reversibly to the carbonyl
group of another aldehyde or ketone…known
as aldol condensation
Simplest is the combination of two
acetaldhyde molecules due to treatment with
an aqueous base
61
62



Step 1…base removes -H to form enolate
anion
Step 2…enolate anion adds to the carbonyl
carbon of another acetaldehyde molecule,
making a new C-C bond
Step 3…alkoxide ion form in step 2 accepts a
proton from the solvent, thus regenerating the
OH- needed for the first step
63



3-hydroxyaldehydes are always formed
Since -C acts as a nucleophile, the product
always has just one C between the aldehyde
and alcohol C’s
Does not matter how long the C chain is in the
starting aldehyde
64


Enolate anion of one carbonyl cpd can be
made to add to the carbonyl carbon of
another cpd
Consider acetaldehyde and benzaldehyde
(has no -H) when treated with base
65