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STRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group COOH
• the bonds are in a planar arrangement
STRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group COOH
• the bonds are in a planar arrangement
• include
a carbonyl (C=O) group
a hydroxyl (O-H) group
and
HOMOLOGOUS SERIES
Carboxylic acids form a homologous series
HCOOH
CH3COOH
C2H5COOH
HOMOLOGOUS SERIES
Carboxylic acids form a homologous series
HCOOH
CH3COOH
C2H5COOH
With more carbon atoms, there can be structural isomers
C3H7COOH
(CH3)2CHCOOH
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 with the C in COOH being 1
• as in alkanes, prefix with alkyl substituents
• side chain positions are numbered relative to Carbon atom number 1
e.g.
CH3 - CH(CH3) - CH2 - CH2 - COOH is called 4-methylpentanoic acid
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 with the C in COOH being 1
• as in alkanes, prefix with alkyl substituents
• side chain positions are numbered relative to Carbon atom number 1
BUTANOIC ACID
2-METHYLPROPANOIC ACID
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
HCOOH
CH3COOH
C6H5COOH
Systematic name
methanoic acid
ethanoic acid
benzenecarboxylic acid
(trivial name)
formic acid
acetic acid
benzoic acid
origin of name
latin for ant
latin for vinegar
from benzene
CHEMICAL PROPERTIES
Carboxylic acids are weak acids. They can donate protons, but they
only partially dissociate into their ions.
weak acids
CH3COOH (aq)
CH3COO¯(aq)
+ H+(aq)
CHEMICAL PROPERTIES
Carboxylic acids display typical reactions of an acid and form salts,
called carboxylates:
1. acid + base  salt + water, eg.
CH3COOH + NaOH (aq) ——> CH3COO¯Na+ (aq) + H2O (l)
ethanoic acid
sodium ethanoate
2. acid + carbonate  salt + water + CO2, eg.
CH3COOH + NaCO3 (aq) ——> CH3COO¯Na+ (aq) + H2O (l) + CO2 (g)
ethanoic acid
sodium ethanoate
QUALITATIVE ANALYSIS
Carboxylic acids are strong enough acids to release CO2 from carbonates.
Phenols are also acidic but not are not strong enough to release CO2
ESTERIFICATION
Reagent(s)
alcohol + strong acid catalyst (e.g. conc. H2SO4 )
Conditions
reflux
Product
ester
Equation
e.g. CH3CH2OH(l) + CH3COOH(l)
ethanol
ethanoic acid
CH3COOC2H5(l) + H2O(l)
ethyl ethanoate
ESTERIFICATION
Reagent(s)
alcohol + strong acid catalyst (e.g. conc. H2SO4 )
Conditions
reflux
Product
ester
Equation
Notes
e.g. CH3CH2OH(l) + CH3COOH(l)
ethanol
ethanoic acid
CH3COOC2H5(l) + H2O(l)
ethyl ethanoate
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
ESTERIFICATION
Reagent(s)
alcohol + strong acid catalyst (e.g conc. H2SO4 )
Conditions
reflux
Product
ester
Equation
e.g. CH3CH2OH(l) + CH3COOH(l)
ethanol
ethanoic acid
CH3COOC2H5(l) + H2O(l)
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
methanol

ethanoic acid
CH3COOCH3 + H2O
METHYL ETHANOATE
ESTERS
Nomenclature
first part from alcohol, second part from acid
e.g. methyl ethanoate CH3COOCH3
METHYL ETHANOATE
ETHYL METHANOATE
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
METHYL ETHANOATE
ETHYL METHANOATE
Preparation
From carboxylic acids or acyl chlorides
Reactivity
Unreactive compared with acids and acyl chlorides
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
METHYL ETHANOATE
ETHYL METHANOATE
Preparation
From carboxylic acids or acyl chlorides
Reactivity
Unreactive compared with acids and acyl chlorides
Isomerism
Esters are structural isomers of carboxylic acids
STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
Classification
Functional Group
Name
CARBOXYLIC ACID
ESTER
R-COOH
R-COOR
PROPANOIC ACID
METHYL ETHANOATE
Physical properties
O-H bond gives rise
to hydrogen bonding;
get higher boiling point
and solubility in water
No hydrogen bonding
insoluble in water
Chemical properties
acidic
reacts with alcohols
fairly unreactive
hydrolysed to acids
USES OF ESTERS
Despite being fairly chemically unreactive, esters are useful as ...
• flavourings
apple
pear
banana
pineapple
rum
• solvents
nail varnish remover - ethyl ethanoate
• plasticisers
2-methylbutanoate
3-methylbutylethanoate
1-methylbutylethanoate
butylbutanoate
2-methylpropylpropanoate
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER
CARBOXYLIC ACID + ALCOHOL
HCOOH
METHANOIC
ACID
ETHYL METHANOATE
+
C2H5OH
ETHANOL
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER
CARBOXYLIC ACID + ALCOHOL
HCOOH
METHANOIC
ACID
ETHYL METHANOATE
METHYL ETHANOATE
+
C2H5OH
ETHANOL
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER
CARBOXYLIC ACID + ALCOHOL
HCOOH
+
METHANOIC
ACID
C2H5OH
ETHANOL
ETHYL METHANOATE
CH3COOH
ETHANOIC
ACID
METHYL ETHANOATE
+
CH3OH
METHANOL
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
+ H2 O
alkaline
CH3COOCH3 + NaOH
CH3COOH
+
CH3OH
——> CH3COO¯ Na+ + CH3OH
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
+ H2 O
alkaline
CH3COOCH3 + NaOH
CH3COOH
+
CH3OH
——> CH3COO¯ Na+ + CH3OH
If the hydrolysis takes place under alkaline conditions,
the organic product is a water soluble ionic salt
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
+ H2 O
alkaline
CH3COOCH3 + NaOH
CH3COOH
+
CH3OH
——> 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
——>
CH3COOH
+
NaCl
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)
CH2OH
CHOH
CH2OH
Saponification
•
•
•
•
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
ACYL CHLORIDES
Nomenclature
Chemical
Properties
Named from the corresponding carboxylic acid
remove -ic add -yl chloride
CH3COCl
ethanoyl chloride
C6H5COCl
benzene carbonyl (benzoyl) chloride
•
•
•
•
colourless liquids which fume in moist air
attacked at the positive carbon centre by nucleophiles
these include water, alcohols, ammonia and amines
undergo addition-elimination reactions
ACYL CHLORIDES
Reagent
Water
Product(s)
carboxylic acid + HCl
(fume in moist air / strong acidic solution formed)
Conditions
room temperature
Equation
CH3COCl(l)
Mechanism
addition-elimination
+ H2O(l) ——>
CH3COOH(aq) + HCl(aq)
ACYL CHLORIDES
Reagent
Alcohols
Product(s)
ester + hydrogen chloride
Conditions
reflux in dry (anhydrous) conditions
Equation
CH3COCl(l)
Mechanism
addition-elimination
Note
+ CH3OH(l) ——>
CH3COOCH3(l) + HCl(g)
esters can also be made from acids and alcohols
via carboxylic acids
slower, reversible, low yield
via acyl chlorides
faster, better yield, must be dry
ACYL CHLORIDES
Reagent
Ammonia
Product(s)
amide + hydrogen chloride
Conditions
Low temperature and excess ammonia; vigorous reaction.
Equation
CH3COCl(l) + NH3(aq) ——>
CH3COCl(l) + 2NH3(aq) ——>
or
Mechanism
addition-elimination
CH3CONH2(s) + HCl(g)
CH3CONH2(s) + NH4Cl(s)
ACYL CHLORIDES
Reagent
Amines
Product(s)
N-substituted amide + hydrogen chloride
Conditions
anhydrous
Equation
Mechanism
CH3COCl + C2H5NH2 ——> CH3CONHC2H5 + HCl
or CH3COCl + 2C2H5NH2 ——> CH3CONHC2H5 + C2H5NH3Cl
addition-elimination - similar to that with ammonia.
REVISION CHECK
What should you be able to do?
Recall and explain the physical properties of carboxylic acids
Recall the structures of carboxylic acids, esters and acyl chlorides
Recall the acidic properties of carboxylic acids
Recall and explain the esterification of carboxylic acids
Write balanced equations representing any reactions in the section
Recall and explain the structure and naming of esters
Recall the methods for making esters
Recall the conditions for, and products of, the hydrolysis of esters.
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AN INTRODUCTION TO
CARBOXYLIC ACIDS
AND THEIR DERIVATIVES
THE END
© JONATHAN HOPTON & KNOCKHARDY PUBLISHING