LECTURE NOTE SK025 (ORGANIC) KMKt

EXAMPLE:

O

cyclopentane → cyclopentanone

17

SIMPLE KETONE

Structure IUPAC name Common name

O propanone Acetone
H3C C CH3

O butanone ethyl methyl
H3C C CH2CH3 ketone

O pentan-2-one @ Methyl propyl
H3C C CH2CH2CH3 2-pentanone ketone

18

SIMPLE KETONE

Structure IUPAC name Common name
O pentan-3-one @
Diethyl ketone
H3CCH2 C CH2CH3 3-pentanone
O Acetophenone
C CH3 phenylethanone (methyl phenyl

ketone)

O diphenylmethanone
C Benzophenone

(diphenyl ketone)

19

The longest chain with carbonyl group is
numbered so that C in carbonyl group gets the
smallest number.

EXAMPLE:

O

12 3 C4 5
H3C5 C4 H2 C3 H2
2 C1 H3

pentan-2-one or 2-pentanone

20

EXAMPLE:

1 23 21

CH2 C CH3

O

1-cyclopentyl propan-2-one

@ 1-cyclopentyl-2-propanone

Refer : pg 808, Wade., Organic Chemistry, 17th Ed, Prentice Hall

EXAMPLE:

O
1C 2CH2 3CH3

1-cyclopentyl propan-1-one

22

EXAMPLE: O

6 12

53

CH3 4 CH CH3
CH3

3-isopropyl -5-methylcyclohexanone

23

EXAMPLE:

O 3

1
2

1-phenyl propan-1-one

24

EXAMPLE:

2 34 6
1 5
O

hex-4-en-3-one @ 4-hexene-3-one

25

EXAMPLE: 3 5 Br
23 41
1
5 4 2

Br O O

1,5-dibromopentan-2,4-dione

26

EXAMPLE:

O

CH3 O

5-methyl cyclohexan-1,3-dione

27

Exercise:

Draw all structural formulae for carbonyl
compounds with molecular formula C5H10O and
give the IUPAC name.

(Hint : 7 possible carbonyl structures)

Answer : Possible structural formulae:
1) Pentanal
2) 3-methylbutanal
3) 2-methylbutanal
4) 2,2-dimethylpropanal
5) 2-pentanone
6) 3-pentanone
7) 3-methyl-2-butanone

28

Learning Outcomes:

9.2 a) Preparation

Explain the preparation of
carbonyl compounds through:
i. Ozonolysis of alkene.
ii. Friedel-Crafts acylation to

produce aromatic ketone.
iii. Oxidation of alcohol.

9.2 Preparation of Carbonyl Compound

I. Ozonolysis of alkene.

O
C II. Friedel-Crafts Acylation

III. Oxidation of Alcohols

30

I. Produces:
Ozonolysis of alkene.

aldehyde or

ketone or both.

RR i) O3 R R
CC ii) Zn/H2O CO
+O C
RH R H

Alkene Ketone Aldehyde

Refer 5.2 k(i) 31

Example :

i) O3 HH
ii) Zn / H2O O C CH2 CH2 CH2 CH2 C O

CH3 i) O3 CH3

H3C C CHCH2CH3 ii) (CH3)2S H3CC O +

O CHCH2CH3

(CH3)2S - Dimethylsulfide 32

II. Friedel-Crafts Acylation

General reaction

+ R O Cl AlCl3 O
C CR

Benzene Acyl chloride @ Aromatic ketone
Acid chloride
to prepare
Refer 6.3 a aromatic ketones

33

1O OXIDATION 2O
Alcohol OF ALCOHOL Alcohol

Mild Refer 8.4 b Mild/Strong
Oxidizing Oxidizing
Agent
Agent

yield yield
ALDEHYDE KETONE

Oxiziding agent : KMnO4 / H+, ∆ 34
K2Cr2O7 / H+, ∆
PCC, CH2Cl2
CrO3/H+
PCC- pyridinium chlorochromate

Example :

CH3CH2OH PCC H
CH2Cl2
Ethanol CH3—C—O

Ethanal

CH3CH(OH)CH3 KMnO4 / H+ O
CH3—C—CH3
2-propanol ∆
propanone

35

EXERCISE
a)

Br K2Cr2O7 / H+ Br

H3CCH CHCH3 ∆ H3CCH C CH3
OH O

3-bromo-2-butanol 3-bromo-2-butanone

36

EXERCISE H
b) CH3 C O

H3C CH CH3 i) O3 + ethanal
ii) Zn / H2O
C CHCH3 O
CH3
H3C C CHCH3
3,4-dimethyl-2-pentene CH3

3-methyl-2-butanone

37

EXERCISE AlCl3

c)

O

C Cl +

O
C

benzophenone

38

Learning Outcomes:

9.3 Chemical Properties of Carbonyl Compounds

a) Explain the chemical properties of carbonyl
compounds with reference to:

i. Nucleophilic addition.

ii. Reduction to alcohol.

iii. Condensation with ammonia derivatives.

iv. Oxidation

v. Iodoform Test.

9.3 (a)

REDUCTION TO
ALCOHOL

CHEMICAL CONDENSATION WITH
PROPERTIES AMMONIA DERIVATIVES

OXIDATION

40

C=O is susceptible to nucleophilic addition.

R :Nu-

δ+ δ-

CO

R'

Electrophilic site

In C=O, the electron density is drawn more
towards the O atom making the C atom
deficient in electrons.
Thus, the C atom becomes the site for Nu-
attack.

41

R :Nu- Nu
R C O-
δ+ δ-
R'
CO

R'

When carbonyl C is attacked by Nu-, the
carbonyl  bond is broken and a tetrahedral
intermediate is formed.

Hybridization of sp2 C atom changes to sp3.

42

(b)
(a)

(c)
NUCLEOPHILIC

ADDITION

(e) (d)

43

Addition of HCN

(a) General reaction:

R NaCN R OH
CO Hv2SO4 C

R' R' CN

Aldehyde or HCN (‘in situ’ Product:
ketone and preparation). Cyanohydrin

HCN : mixture of
KCN or NaCN
with H2SO4 @ HCl

44

Example : NaCN OH
H2SO4 |
O C–H
C–H |
CN
benzaldehyde
Cyanohydrin
O NaCN
H2SO4 OH
CH3–C–CH3 |
CH3–C| –CH3
propanone CN

Cyanohydrin

45

Addition of Water

(b) General reaction: R OH
C
R H2O/H+
CO R' OH

R'

Aldehyde or ketone Product:
and Water Hydrate
(gem-diols)

***gem = geminal ( two OH or X bonded to the same C ) 46

Example : H2O/H+ OH
H2O/H+ HC H
O
H CH OH

Methanal Hydrate (gem-diols)

O OH
H3CCH2CCH3 H3CCH2CCH3

Butanone OH

Hydrate (gem-diols)

47

Addition of Alcohols

(c) General reaction: Formation of hemiacetal

R H+ R OH
C
C O + R’OH
H OR'
H

Aldehyde and alcohols Product:
Hemiacetal

48

Addition of Alcohols

(c) General reaction: Formation of acetal

R OH R OR''
C + R’’OH H+ C

H OR' H OR'

Hemiacetal Product:
In acidic catalyst Acetal
Further react with alcohols
49

Example : H+ OH

O CH3OH C
C H

H OCH3

cyclohexanecarbaldehyde cyclohexyl(methoxy)methanol

OH H+ OCH3
C
C CH3OH
H H
OCH3
OCH3
50

Addition of Alcohols

(c) General reaction: Formation of hemiketal

R R OH
C O+ R’OH H+ C OR'

RR

Ketone and alcohols Product:
Hemiketal

51

Addition of Alcohols

(c) General reaction: Formation of ketal

R OH R OR''
C + R’’OH H+ C

R OR' R OR'

Hemiketal Product:
In acidic catalyst Ketal
Further react with alcohols

52

Example : CH3OH H+

O
H3C CH2CH2CCH2CH3

3-hexanone

OH
H3C CH2CH2CCH2CH3

OCH3

3-methoxy-3-hexanol

53

Addition of Sodium bisulphite, NaHSO3

(d) General reaction:

R R OH
C O NaHSO3
C

R R SO3-Na+

Aldehyde Or Ketone Product:
And NaHSO3 Bisulphate salt

Uses of for purification of aldehyde @ ketone from other non-
Reaction soluble organic compounds.

54

Example : NaHSO3 OH
CH3–C|| –SO3-Na+
O
CH3C–H H

Ethanal Bisulphate salt

O NaHSO3 OH
CH3–C–CH3 CH3–C|| –SO3-Na+

Propanone CH3

Bisulphate salt

55

Addition of Grignard Reagent, RMgX

(e)

+ + +

Methanal Other Ketone
Aldehyde

HCHO RCHO RCOR’

Followed Followed Followed
by by by

hydrolysis hydrolysis hydrolysis

1O Alcohol 2O Alcohol 3O Alcohol

*Hydrolysis : + aqueous acid @ diluted acid, H3O+

Example :

H H
H C OMgBr
H3C CH2 MgBr + H C O ether
CH2CH3
Ethylmagnesium methanal
bromide H3O+

Mg(OH)Br + H
H C OH

CH2CH3

Propan-1-ol

57

Example :

CH3 ether CH3
H C OMgBr
H3C CH2 MgBr + H C O
CH2CH3
Ethylmagnesium ethanal
bromide H3O+

Mg(OH)Br + CH3
H C OH

CH2CH3

butan-2-ol

58

Example :

CH3 MgBr CH3 CH3
i. CH3 C O , ether CH3 C OH

ii. H3O+ CH3

methylmagnesium

bromide 2-methylpropan-2-ol
+

Mg(OH)Br

59

ii) Reduction of Carbonyl, C=O to Alcohol

(a) (b)
Lithium aluminium hydride,
LiAlH4 Sodium borohydride,
followed by H3O+
NaBH4 in
REDUCING methanol, CH3OH @
AGENTS ethanol, CH3CH2OH

(c)

Catalytic hydrogenation

H2/catalyst
*catalyst: Pt, Ni, Pd-C

60

Example : 1. LiAlH4 H
2. H3O+
H H3C CH2 C O H
H3C CH2 C O H

propanal propan-1-ol

O H2 /Ni OH
C CH3 
C CH3
acetophenone H

1-phenylethanol

61

KEEP IN MIND!

When a compound contains both C=O and C=C,
selective reduction of one functional group by
proper choice of reducing agent :

i. LiAlH4 OH
ii. H3O+ H

O NaBH4 in OH
methanol H

H2 /Ni OH

H

62

iii) Condensation with Ammonia Derivatives

Condensation Process: Addition reaction
Followed by dehydration reaction
(elimination smaller molecule)

Ammonia : NH3 Act as nucleophile

Ammonia Derivaties : YNH2

Example : R-NH2 (10 amine)

HO-NH2 (hydroxylamine)

NH2-NH2 (hydrazine)

iii) Condensation with Ammonia Derivatives

A condensation reaction

H addition C OH

I Y-N-H

C=O + Y–N-H Carbinolamine
‘Unstable intermediate’
which two molecules combine to
form a larger molecule

the elimination of a -H2O
*smaller molecule

C

Y-N

Compound with imine group (C=N)

*Smaller molecule :water, H2O ammonia, NH3 or HCl. 64

Example : H H NO2 2,4-DNPH
CH3 || (Brady’s
| H—N-N reagent)

CH3—C O + NO2
||
|| 2,4-dinitrophenylhydrazine

H2O + CH3 H NO2 NO2 yellow @
|| orange
CH3—C N-N precipitate

2,4-dinitrophenylhydrazone

65

iii) Condensation with Ammonia Derivatives

NH3 Name Product Name
derivatives C=N-R or Imine
R-NH2 or primary C=N-Ar Hydrazone
amine C=NNH2 Oxime
Ar-NH2
hydrazine C=N-OH
NH2NH2

NH2-OH hydroxyl
amine

66