LECTURE NOTE SK025 (ORGANIC) KMKt

Arrange the solubility of compounds in water in descending order.

COOH COOH COOH COOH COOH

CH3CH2CH2 CH3CHCH2CH2 CH3CH2CH2CH2

COOH COOH COOH COOH COOH

> > >CH3CHCH2CH2
CH3CH2CH2 CH3CH2CH2CH2

10.2 Physical Properties of Carboxylic Acids

b) Explain the acidity of : (C2, C3 & C4)

i. Carboxylic acid in comparison with alcohol &
phenol

ii. halogenated carboxylic acids
based on the ;
• number of halogens
• position of halogens

❖ Include inductive effect or function of halogen
as Electron Withdrawing Group (EWG)

ACIDITY

➢ Carboxylic acid is relatively a weak acid however it is
stronger than phenol & alcohol.

OH

O > H2O > R OH

R C OH >

➢ Two factors that influence the acidity of carboxylic acid are:
❑ Resonance effect
❑ Inductive effect

(Inductive effect is the shift of electron density from one atom
to another to form a polar bond)

RESONANCE EFFECT IN CARBOXYLATE ION

➢ Carboxylic acid dissociate in water to form carboxylate ion.

O O

+R C H2O H3C C + H3O+

OH -

O

carboxylic acid carboxylate ion

➢ Carboxylate ion is stabilized through resonance where the electrons
are delocalized over two electronegative oxygen atoms (resonance
stabilization).

➢ Due to the resonance stabilization of the carboxylate ion, carboxylic
acid is more acidic than phenol and alcohol.

RESONANCE EFFECT IN PHENOXIDE ION

➢ Phenol dissociate in water to form phenoxide ion.
➢ In phenoxide ion, the electrons are delocalized within

the benzene ring.

OH

+ H2O

phenol resonance structure of phenoxide ion

➢ The resonance structure of carboxylate ion is more
stable than the phenoxide ion.

➢ Therefore carboxylic acid are more acidic than phenol.

* The ability to spread the negative charge over four atoms rather than
concentrated it on just one atom produces more stable phenoxide ion.

➢ Alcohol dissociate in water to form alkoxide ion.
➢ Alcohol is the least acidic compare to carboxylic acid and

phenol due to the electrons are localized at oxygen

atom in alkoxide ion.

R O H + H2O +R O- H3O+

alcohol alkoxide ion

➢ Thus alcohol is less acidic than phenol.

INDUCTIVE EFFECT

➢ Substituent group that attached to the carbon of the carboxyl
plays major role in determining the acidity of a carboxylic
acid.

Electron withdrawing group Electron donating group
O
O

EWG C EDG C
O- O-

An electron withdrawing group, An electron donating group, EDG
EWG that attached to a carboxylate will destabilise the carboxylate ion and
ion will stabilises the carboxylate ion decreases acidity.
and increases acidity.

Example : NO2, -F, -Cl, -Br, -I Example :

-NH2, -NHR,-NR2,-OH,-OR,-NHCOR,-R

How electron withdrawing group increases
the acidity ?

• Electron Withdrawing Groups(EWG) reduce the electron
density of –O-H bond.

• Thus the –O-H bond becomes weaker and H+ can be
easily released and form stable carboxylate ion.

• An electron withdrawing group, EWG that attached to a
carboxylate ion will stabilises the carboxylate ion.

• The compound is said to be more acidic.

• There are two factors that can effect the stability of
carboxylate ion through inductive effect :
✓ Number of halogens
✓ Position of halogens

NUMBER OF HALOGENS

Cl O Cl O

CH3 C C OH and CH3 CH C OH

Cl

AB

➢ Compound A contains 2 atoms of Cl that make the bond of –O-H

bond weaker than Compound B (with only one Cl atom). Thus, H+

is easily donated.

➢ Compound A contains more electron withdrawing group (EWG), Cl,

that attached to carboxylate ion. The electron withdrawing group

increase the stability of carboxylate ion.

➢ Thus, acidity :

Cl O Cl O

>CH3 C C OH CH3 CH C OH

Cl

POSITION OF HALOGENS

Cl O Cl O

CH3CH2CH C OH and CH2CH2CH2 C OH

CD

➢ The distance between Cl atom and carboxyl group in Compound C is
nearer compared to Compound D.

➢ The –O-H bond in Compound C is weaker than in Compound D, so H+
is easily donated.

➢ The stability of carboxylate ion of compound C increases as the
distance between Cl atom and carboxyl group decreases.

➢ Thus, acidity : Cl O Cl O

CH3CH2CH C OH > CH2CH2CH2 C OH

Carboxylic acid pKa ➢ pKa ↓ , Ka ↑, acidity ↑

O 4.74 ➢ Cl is an electron withdrawing
CH3C OH group(EWG), therefore reduce the
2.86 electron density of –O-H bond.
Cl O
CH2C OH ➢ Thus the O-H bond in molecule
becomes weaker and H+ can be
easily released.

➢ The presence of Cl stabilizes the carboxylate ion through inductive
effect by withdrawing electron density from the carboxylate ion.

➢ Therefore a more stable carboxylate ion is formed which makes the
acidity is higher.

➢ Thus, acidity : Cl O O
CH3C OH
>CH2C OH

FO Cl O

CH3 CH C OH and CH3 CH C OH

EF

➢ Both F and Cl are electron withdrawing groups(EWG).

➢ The electronegativity of F > Cl, so F is able to attract electron stronger

than Cl.

➢ The electron density of –O-H bond in Compound E is less, thus the
–O-H bond is weaker than in Compound F. Therefore, H+ is easily
donated.

➢ The presence of more electronegative of F atom in compound E

stabilizes the carboxylate ion through inductive effect by

withdrawing electron density from the carboxylate ion compared to

compound F.

➢ Thus, acidity : FO Cl O

CH3 CH C OH >

CH3 CH C OH

10.3 Preparation of Carboxylic Acids
a) Explain the preparation of carboxylic acid through :
(C3 &C4)
i. Oxidation of alkylbenzene, alcohol and aldehyde

ii. Hydrolysis of nitrile compound

iii. Carbonation of Grignard reagent

PREPARATION OF CARBOXYLIC ACIDS

➢ Oxidation of Alkylbenzene

R KMnO4 , H+ COOH

 Cl
COOH + CO2 + H2O
(R= alkyl group) KMnO4 , H+
Cl 
CH3

CH CH3

Example of strong oxidizing agent:

KMnO4/H2SO4, or K2Cr2O7/H2SO4,  or Na2Cr2O7/H2SO4, 

HR oxidizing R
R C OH PCC in CH2Cl2 C O agent C

O

H H HO

1o alcohol aldehyde carboxylic acid

Strong oxidizing agent

➢ Oxidation of 1o Alcohol

H KMnO4 , H+ H3C O
H3C C OH  C

H HO
carboxylic acid
1o alcohol
H3O+ H3C O
➢ Oxidation of Aldehyde  C

H3C HO

C O + Na2Cr2O7 carboxylic acid

H
aldehyde

➢ Hydrolysis of nitrile compound

Hydrolysis of nitrile yields a carboxylic acid that has one
carbon atom longer than its alkyl halide.

R-CN H2O R-COOH
H+

H2O
H+

➢ Carbonation of Grignard Reagents

General reaction :

R—MgX i) O C O R—COOH + Mg(OH)X

ii) H2O, H+

CH2 MgBr CH2 COOH

i) CO2 + Mg(OH)Br
ii) H2O, H+

10.4 Chemical Properties of Carboxylic Acids
a) Explain the chemical properties with reference to :

(C3 & C4)

i. Neutralisation with a base
ii. Reaction with electropositive metals such as Na,

K, Mg or Ca
iii. Reduction with LiAlH4 followed by H2O
iv. Acyl chloride formation
v. Anhydride formation
vi. Esterification

vii. Amide formation

CHEMICAL PROPERTIES
OF CARBOXYLIC ACIDS

➢ Neutralisation with a base

Carboxylic acids react with base to give metal carboxylate
salts.

General equation:

OO

RC + NaOH RC + 1/2H2O

OH - Na+

O

OR

O O

R C + NaHCO3 RC + CO2 + 1/2 H2O
@
- Na+
OH Na2CO3
O

COOH COO-Na+

+ NaOH + H2O

Benzoic acid Sodium benzoate

O O + CO2 + H2O
CH3 CH2 C OH + NaHCO3 CH3 CH2 C O-Na+

Propanoic acid Sodium propanoate

➢ Reaction with electropositive metals such as Na, K,
Ca, Mg

General equation:

O O
R C O-M+ + H2
R C OH + M
(metal)

Cl Cl
COOH COO -K+
+K + H2

➢ Reduction with LiAlH4 followed by H2O

Carboxylic acid are reduced to primary alcohols by

reaction with lithium aluminium hydride, LiAlH4 followed
by hydrolysis.

General equation:

O

R C OH i) LiAlH4 R CH2 OH
ii) H2O
1o alcohol

O

CH3CH C OH i) LiAlH4 CH3CHCH2 OH
ii) H2O CH3
1o alcohol

CH3

➢ Acid Chloride Formation
General equation:

o thionyl chloride, SOCl2

OO

R C OH SOCl2 R C Cl + SO2 + HCl

White fume

o phosphorous pentachloride, PCl5

OO

R C OH PCl5 R C Cl + POCl3 + HCl

White fume

o phosphorous trichloride, PCl3

OO

R C OH PCl3 R C Cl + H3PO3

O SOCl2 O
CH3 CH C OH CH3 CH C Cl + SO2 + HCl

CH3 CH3

O PCl5 O
CH3 CH C OH CH3 CH C Cl + POCl3 + HCl

CH3 CH3

O PCl3 O
CH3 CH C OH CH3 CH C Cl + H3PO3

CH3 CH3

➢ Acid anhydride formation

▪ Acid anhydrides can be prepared from carboxylic acids
in the presence phosphorous pentoxide, P2O5, a
strong dehydrating agent

General equation:

OO P2O5 OO

R C OH + R' C OH R C O C R' + H2O

carboxylic acid carboxylic acid acid anhydride

OO P2O5 OO
 CH3 C O C CH2 CH3
CH3 C OH + CH3CH2 C OH

ethanoic propanoic anhydride

▪ Acid anhydride also can be prepared by reacting
carboxylic acid with acyl chloride in the presence
of pyridine.

General equation:

OO OO

Pyridine R C O C R' + HCl

R C OH + Cl C R' acid anhydride

carboxylic acid acid chloride

O O Cl Pyridine O O
CH3 CH2 C CH3CH2C O C CH3
OH + CH3 C

➢ Esterification

Carboxylic acids react with alcohols in the presence of
mineral acid catalyst to produce ester

General equation:

O conc.H2SO4 O

R C OH + R’ OH R C OR' + H O
2
carboxylic acid alcohol ester

O O
CH3 CH2 C O CH2 CH3 + H2O
CH3 CH2 C OH + HOCH2CH3 conc.H2SO4
 Ethyl propanoate

Propanoic acid ethanol

➢ Amide formation

Reaction of carboxylic acids with an ammonia or amine
followed by heating.

General equation:

OO

R C OH Excess NH3 R C NH2 + H2O
 1o amide

O 1o amine O
R C NHR + H2O
R C OH RNH2
2o amide

O
O 2o amine R C NR2 + H2O

R C OH R2NH 3o amide


CH3 O excess NH3 CH3 O + H2O
H C C OH  H C C NH2

CH3 CH3

CH3 O CH3 NH2 CH3 O
H C C OH
 H C C NH(CH3) + H2O
CH3
CH3

CH3 O CH3NH CH3 O
H C C OH
CH3 H C C N(CH3)2 + H2O
CH3
 CH3

➢ Amide is not favourably prepared directly from a
carboxylic acid due to its reactivity.

➢ It is usually prepared through acid chloride which is
more reactive than carboxylic acid.

➢ The reaction of carboxylic acids with SOCl2/PCl3/PCl5
formed acyl chloride which is then react with
ammonia or amine.

General equation:

OO O
R C NH2
R C SOCl2 or PCl3 C Cl excess NH3
 Amide
OH R
or PCl5

Carboxylic acid Acid chloride

Amides formation through acyl chloride

OO O

R C OH SOCl2 or PCl3 R C Cl excess NH3 R C NH2
 1o amide
or PCl5

O O 1o amine O

SOCl2 or PCl3 RNH2 R C NHR

R C OH or PCl5 R C Cl 2o amide

O O 2o amine O
R2NH
R C OH SOCl2 or PCl3 R C Cl  R C NR2

or PCl5 3o amide

10.4 Chemical Properties of Carboxylic Acids
b) Explain the reducing property of methanoic acid with :
(C3 & C4)
i. KMnO4/ H3O+
ii. Tollens’ reagent

Methanoic acid, HCOOH as a reducing agent

carbonyl O carboxyl
H C OH

o Methanoic acid molecule has both carboxyl and
carbonyl group

o It shows the properties of both carboxylic acid and
aldehyde

o It also shows reducing properties in reactions with
acidified KMnO4 or K2Cr2O7 and Tollens’ reagent.

O KMnO4 /H+ ,heat CO2 + H2O + Mn2+
H C OH
Pale pink
O
H C OH Ag(NH3)2+ OH- Ag + CO2 + H2O

Silver mirror

10.4 Chemical Properties of Carboxylic Acids
c) Outline the synthesis of compounds related to
reactions of carboxylic acids. (C3 & C4)

* Limit to maximum 4 steps only

Propose a synthetic route for the preparation of
cyclopentanecarboxylic acid from cyclopentane via
Grignard reagent.

Some reactions of organic compounds W to Z are shown

in the flow chart below. Suggest the structures of W, X, Y

and Z.

Sodium hydroxide PCl5
WX
Y
C7H5O2Na C7H6O2 C7H6OCl

Ethanol and
Concentrated
Sulphuric acid

Z
C9H10O2

X : COOH W : COO-Na+ Y : COCl Z : COOCH2CH3

10.4 Chemical Properties of Carboxylic Acids

d) Explain the preparation of synthetic polymers through
condensation polymerisation to produce polyamides
(e.g Kevlar, nylon 6, nylon 6,6) and polyester (e.g
Dacron/terylene). (C3 & C4)

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION

• A chemical process in which 2 monomers react to form a larger
molecule and eliminate a smaller molecule.

• Formed condensation polymers (polyamides and polyester).
• The monomers must have at least two functional groups to act as

the reactive ends.

When a carboxylic acid with two –COOH groups reacts with an
amine with two –NH2 groups, a polyamide is formed.
When a carboxylic acid with two –COOH groups reacts with an
alcohol with two –OH groups, a polyester is formed.

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION
(POLYAMIDES): NYLON 6,6

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION
(POLYAMIDES): NYLON 6

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION
(POLYAMIDES): KEVLAR

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION
(POLYESTER): DACRON

PREPARATION OF SYNTHETIC POLYMERS

CONDENSATION POLYMERISATION
(POLYESTER): TERYLENE



Edited By : Revised By :

MS ZS
…………………………………………………… ……………………………………………………

Approved By :

ZA
……………………………………………………

CHAPTER 11

Learning Outcomes

11.1 INTRODUCTION OF AMINES

At the end of the lesson, you should be able to:

a) Give the name of aliphatic and aromatic amines
according to the IUPAC nomenclature (parent chain
≤ C10) C2

b) State the common names of amines with parent
chain ≤ C5 C1
c) Give the structural formulae of amines in 11.1 (a)
C2
d) Classify primary, secondary and tertiary amines. C2

2

11.1 (a) Nomenclature Of Amines
11.1 (c) Structural Formula

IUPAC NAMES

• Determine the longest continuous chain of carbon
atoms.

• The –e ending in the alkane name is changed to –
amine, and a number shows the position of the amino
group.

• Other substituents on the carbon chain are given
numbers, and prefix N- is used for each substituent.

EXAMPLE:

WSOALD:E8:Ce4Hde3.,dp.,N.9pH4.8224*8* 3–methyl–1–butanamine
CACRHE3YC:H5CeHdC., Hp2.913 (1o amine)
MU4R: 63ed2., p1.893*

NOR: p.239

3 2 4,4–dimethylcyclohexanamine
(1o amine)
H3C 4 1 NH2

H3C 6

5