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. 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. 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. 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.
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. 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. 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. 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. 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. Physical Properties : solubility
• Ketones can form hydrogen bonds with water and therefore low
molecular weight ketones have appreciable water solubility
12
12
14. 2.1 Oxidation of 2 °Alcohol
• Ketones can be made from 2o alcohols by oxidation
* [O] =
• Examples
14
15. 2.2 Friedel – Crafts Acylation
• Aromatic ketones can be made by Friedel-Crafts Acylation
• Examples
15
16. REACTIONS
REDUCTION TO 2 ° ALCOHOL
NUCLEOPHILIC addition
REACTION with grignard reagent
IODOFORM REACTION
16
17. REACTIONS OF KETONES
Reduction
Addition
Condensation
Iodoform reaction
Reaction with Grignard reagent
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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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
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.
