CONTENTS

1
CARBOXYLIC ACIDS

• CONTENTS
• Structure of carboxylic acids
• Nomenclature
• Physical properties of carboxylic acids
• Preparation of carboxylic acids
• Chemical properties of carboxylic acids
• Esters

2
CARBOXYLIC ACIDS

• Before you start it would be helpful to
• Recall the definition of a covalent bond
• Recall the difference types of physical bonding
• Be able to balance simple equations
• Be able to write out structures for simple
  organic molecules
• Understand the IUPAC nomenclature rules for
  simple organic compounds
• Recall the chemical properties of alkanes and
  alkenes

3
STRUCTURE OF CARBOXYLIC ACIDS
contain the carboxyl functional group COOH
the bonds are in a planar arrangement
4
STRUCTURE OF CARBOXYLIC ACIDS
contain the carboxyl functional group COOH
the bonds are in a planar arrangement
include a carbonyl (CO) group and a
hydroxyl (O-H) group
5
STRUCTURE OF CARBOXYLIC ACIDS
contain the carboxyl functional group COOH
the bonds are in a planar arrangement
include a carbonyl (CO) group and a
hydroxyl (O-H) group are isomeric with
esters - RCOOR
6
HOMOLOGOUS SERIES
Carboxylic acids form a homologous series
HCOOH CH3COOH C2H5COOH
7
HOMOLOGOUS SERIES
Carboxylic acids form a homologous series
HCOOH CH3COOH C2H5COOH
With more carbon atoms, there can be
structural isomers
C3H7COOH (CH3)2CHCOOH
8
INFRA-RED SPECTROSCOPY
IDENTIFYING CARBOXYLIC ACIDS USING INFRA RED
SPECTROSCOPY Differentiation Compound O-H
CO ALCOHOL YES NO CARBOXYLIC ACID YES
YES ESTER NO YES ALCOHOL
CARBOXYLIC ACID ESTER O-H
absorption O-H CO absorption
CO absorption
9
NAMING CARBOXYLIC ACIDS
Acids are named according to standard IUPAC
rules select the longest chain of C atoms
containing the COOH group remove the e and
add oic acid after the basic name number the
chain starting from the end nearer the COOH
group as in alkanes, prefix with alkyl
substituents side chain positions are based
on the C in COOH being 1 e.g. CH3 -
CH(CH3) - CH2 - CH2 - COOH is called
4-methylpentanoic acid
10
NAMING CARBOXYLIC ACIDS
Acids are named according to standard IUPAC
rules select the longest chain of C atoms
containing the COOH group remove the e and
add oic acid after the basic name number the
chain starting from the end nearer the COOH
group as in alkanes, prefix with alkyl
substituents side chain positions are based
on the C in COOH being 1
METHANOIC ACID ETHANOIC ACID PROPANOIC ACID
11
NAMING CARBOXYLIC ACIDS
Acids are named according to standard IUPAC
rules select the longest chain of C atoms
containing the COOH group remove the e and
add oic acid after the basic name number the
chain starting from the end nearer the COOH
group as in alkanes, prefix with alkyl
substituents side chain positions are based
on the C in COOH being 1
BUTANOIC ACID 2-METHYLPROPANOIC ACID
12
NAMING CARBOXYLIC ACIDS
Acids are named according to standard IUPAC rules
Many carboxylic acids are still known under
their trivial names, some having been called
after characteristic properties or their
origin. Formula Systematic name (trivial
name) origin of name HCOOH methanoic
acid formic acid latin for ant CH3COOH
ethanoic acid acetic acid latin for
vinegar C6H5COOH benzenecarboxylic
acid benzoic acid from benzene
13
PHYSICAL PROPERTIES
BOILING POINT Increases as size increases -
due to increased van der Waals forces
101C 118C 141C
164C
14
PHYSICAL PROPERTIES
BOILING POINT Increases as size increases -
due to increased van der Waals forces
101C 118C 141C
164C
Boiling point is higher for straight chain
isomers.
164C 154C
Greater branching lower inter-molecular
forces lower boiling point
15
PHYSICAL PROPERTIES
BOILING POINT Increases as size increases -
due to increased van der Waals forces Carboxylic
acids have high boiling points for their relative
mass The effect of hydrogen bonding on the
boiling point of compounds of similar
mass Compound Formula Mr b. pt.
(C) Comments ethanoic acid CH3COOH 60
118 propan-1-ol C3H7OH 60
97 h-bonding propanal C2H5CHO 58
49 dipole-dipole butane C4H10 58 - 0.5 basic
V der W
16
PHYSICAL PROPERTIES
BOILING POINT Increases as size increases -
due to increased van der Waals forces Carboxylic
acids have high boiling points for their relative
mass arises from inter-molecular hydrogen
bonding due to polar OH bonds
AN EXTREME CASE... DIMERISATION extra
inter-molecular attraction more energy to
separate molecules
17
PHYSICAL PROPERTIES
SOLUBILITY carboxylic acids are soluble in
organic solvents they are also soluble in
water due to hydrogen bonding
18
PHYSICAL PROPERTIES
SOLUBILITY carboxylic acids are soluble in
organic solvents they are also soluble in
water due to hydrogen bonding small
ones dissolve readily in cold water as mass
increases, the solubility decreases benzoic
acid is fairly insoluble in cold but soluble in
hot water
19
CHEMICAL PROPERTIES
ACIDITY weak acids RCOOH H2O(l)
RCOO(aq) H3O(aq) form salts RCOOH
NaOH(aq) gt RCOONa(aq) H2O(l)
20
CHEMICAL PROPERTIES
ACIDITY weak acids RCOOH H2O(l)
RCOO(aq) H3O(aq) form salts RCOOH
NaOH(aq) gt RCOONa(aq)
H2O(l) QUALITATIVE ANALYSIS Carboxylic
acids are strong enough acids to liberate CO2
from carbonates Phenols are also acidic but not
are not strong enough to liberate CO2
21
ESTERIFICATION
Reagent(s) alcohol strong acid catalyst (e.g.
conc. H2SO4 ) Conditions reflux Product ester Equ
ation e.g. CH3CH2OH(l) CH3COOH(l)
CH3COOC2H5(l) H2O(l) ethanol
ethanoic acid ethyl ethanoate
22
ESTERIFICATION
Reagent(s) alcohol strong acid catalyst (e.g.
conc. H2SO4 ) Conditions reflux Product ester Equ
ation e.g. CH3CH2OH(l) CH3COOH(l)
CH3COOC2H5(l) H2O(l) ethanol
ethanoic acid ethyl ethanoate Notes Conc.
H2SO4 is a dehydrating agent - it removes
water causing the equilibrium to move to the
right and thus increases the yield of the
ester
23
ESTERIFICATION
Reagent(s) alcohol strong acid catalyst (e.g
conc. H2SO4 ) Conditions reflux Product ester Equ
ation e.g. CH3CH2OH(l) CH3COOH(l)
CH3COOC2H5(l) H2O(l) ethanol
ethanoic acid ethyl ethanoate Notes Conc.
H2SO4 is a dehydrating agent - it removes
water causing the equilibrium to move to the
right and thus increases the yield of the
ester Naming esters Named from the original
alcohol and carboxylic acid CH3OH
CH3COOH CH3COOCH3 H2O from
ethanoic acid CH3COOCH3 from
methanol METHYL ETHANOATE
24
ESTERS
Structure Substitute an organic group for the H
in carboxylic acids Nomenclature first part from
alcohol, second part from acid e.g. methyl
ethanoate CH3COOCH3
ETHYL METHANOATE
METHYL ETHANOATE
25
ESTERS
Structure Substitute an organic group for the H
in carboxylic acids Nomenclature first part from
alcohol, second part from acid e.g. methyl
ethanoate CH3COOCH3 Preparation From
carboxylic acids or acyl chlorides Reactivity Unr
eactive compared with acids and acyl chlorides
ETHYL METHANOATE
METHYL ETHANOATE
26
ESTERS
Structure Substitute an organic group for the H
in carboxylic acids Nomenclature first part from
alcohol, second part from acid e.g. methyl
ethanoate CH3COOCH3 Preparation From
carboxylic acids or acyl chlorides Reactivity Unr
eactive compared with acids and acyl
chlorides Isomerism Esters are structural
isomers of carboxylic acids
ETHYL METHANOATE
METHYL ETHANOATE
27
STRUCTURAL ISOMERISM FUNCTIONAL GROUP
Classification CARBOXYLIC ACID
ESTER Functional Group R-COOH
R-COOR Name PROPANOIC ACID
METHYL ETHANOATE Physical properties O-H bond
gives rise No hydrogen bonding to
hydrogen bonding insoluble in water get
higher boiling point and solubility in
water Chemical properties acidic
fairly unreactive reacts with alcohols
hydrolysed to acids
28
PREPARATION OF ESTERS
Reagent(s) alcohol carboxylic
acid Conditions reflux with a strong acid
catalyst (e.g. conc. H2SO4 ) Equation
e.g. CH3CH2OH(l) CH3COOH(l)
CH3COOC2H5(l) H2O(l) ethanol
ethanoic acid ethyl ethanoate Notes Conc.
H2SO4 is a dehydrating agent - it removes
water causing the equilibrium to move to the
right and thus increases the yield of the
ester For more details see under
Reactions of carboxylic acids
29
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL
HCOOH C2H5OH METHANOIC
ETHANOL ACID
ETHYL METHANOATE
30
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL
HCOOH C2H5OH METHANOIC
ETHANOL ACID
ETHYL METHANOATE
METHYL ETHANOATE
31
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL
HCOOH C2H5OH METHANOIC
ETHANOL ACID
ETHYL METHANOATE
CH3COOH CH3OH ETHANOIC METHANOL
ACID
METHYL ETHANOATE
32
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL The products of hydrolysis depend on the
conditions used... acidic CH3COOCH3
H2O CH3COOH CH3OH alkaline
CH3COOCH3 NaOH gt CH3COO Na
CH3OH
33
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL The products of hydrolysis depend on the
conditions used... acidic CH3COOCH3
H2O CH3COOH CH3OH alkaline
CH3COOCH3 NaOH gt CH3COO Na
CH3OH If the hydrolysis takes place
under alkaline conditions, the organic
product is a water soluble ionic salt
34
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER WATER CARBOXYLIC ACID
ALCOHOL The products of hydrolysis depend on the
conditions used... acidic CH3COOCH3
H2O CH3COOH CH3OH alkaline
CH3COOCH3 NaOH gt CH3COO Na
CH3OH If the hydrolysis takes place
under alkaline conditions, the organic
product is a water soluble ionic salt
The carboxylic acid can be made by treating the
salt with HCl CH3COO Na HCl
gt CH3COOH NaCl
35
NATURALLY OCCURING ESTERS - TRIGLYCERIDES
triglycerides are the most common component of
edible fats and oils they are esters of the
alcohol glycerol (propane-1,2,3-triol) S
aponification alkaline hydrolysis of
triglycerol esters produces soaps a simple
soap is the salt of a fatty acid as most oils
contain a mixture of triglycerols, soaps are not
pure the quality of a soap depends on the oils
from which it is made
36
USES OF ESTERS
Despite being fairly chemically unreactive,
esters are useful as ... flavourings apple 2-
methylbutanoate pear 3-methylbutylethanoate b
anana 1-methylbutylethanoate pineapple butylbut
anoate rum 2-methylpropylpropanoate
solvents nail varnish remover - ethyl
ethanoate plasticisers