Carboxylic acids and their Derivative

1. AN INTRODUCTION TOAN INTRODUCTION TO
CARBOXYLIC ACIDSCARBOXYLIC ACIDS
AND THEIR DERIVATIVESAND THEIR DERIVATIVES

2. CONTENTS
• Structure of carboxylic acids
• Nomenclature
• Physical properties of carboxylic acids
• Preparation of carboxylic acids
• Chemical properties of carboxylic acids
• Acyl chlorides
• Esters
• Triglycerides and fats
• Biofuels
CARBOXYLIC ACIDSCARBOXYLIC ACIDS

3. STRUCTURE OF CARBOXYLIC ACIDSSTRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group COOH
• the bonds are in a planar arrangement

4. STRUCTURE OF CARBOXYLIC ACIDSSTRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group COOH
• the bonds are in a planar arrangement
• include a carbonyl (C=O) group and
a hydroxyl (O-H) group

5. STRUCTURE OF CARBOXYLIC ACIDSSTRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group COOH
• the bonds are in a planar arrangement
• include a carbonyl (C=O) group and
a hydroxyl (O-H) group
• are isomeric with esters :- RCOOR’

6. Carboxylic acids form a homologous series
HOMOLOGOUS SERIESHOMOLOGOUS SERIES
HCOOH CH3COOH C2H5COOH
With more carbon atoms, there can be structural isomers
C3H7COOH (CH3)2CHCOOH

7. 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
NAMING CARBOXYLIC ACIDSNAMING CARBOXYLIC ACIDS

8. 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
NAMING CARBOXYLIC ACIDSNAMING CARBOXYLIC ACIDS
METHANOIC ACID ETHANOIC ACID PROPANOIC ACID

9. 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
NAMING CARBOXYLIC ACIDSNAMING CARBOXYLIC ACIDS
BUTANOIC ACID 2-METHYLPROPANOIC ACID

10. NAMING CARBOXYLIC ACIDSNAMING 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

11. Greater branching = lower inter-molecular forces = lower boiling point
Boiling point is higher for “straight” chain isomers.
101°C 118°C 141°C 164°C
164°C 154°C
PHYSICAL PROPERTIESPHYSICAL PROPERTIES
BOILING POINT
Increases as size increases - higher induced dipole-dipole interactions

12. PHYSICAL PROPERTIESPHYSICAL PROPERTIES
BOILING POINT
Increases as size increases - higher induced dipole-dipole interactions
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 + h-bonding
propan-1-ol C3H7OH 60 97 + h-bonding
propanal C2H5CHO 58 49 + permanent dipole-dipole
butane C4H10 58 - 0.5 induced dipole-dipole

13. PHYSICAL PROPERTIESPHYSICAL PROPERTIES
BOILING POINT
Increases as size increases - higher induced dipole-dipole interactions
Carboxylic acids have high boiling points for their relative mass
• arises from inter-molecular hydrogen bonding due to polar O—H bonds
AN EXTREME CASE... DIMERISATION
• extra inter-molecular attraction = more energy to separate molecules
HYDROGEN
BONDING

14. PHYSICAL PROPERTIESPHYSICAL 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
HYDROGEN
BONDING

15. PREPARATION OF CARBOXYLIC ACIDSPREPARATION OF CARBOXYLIC ACIDS
Oxidation of aldehydes RCHO + [O] ——> RCOOH
Oxidation of Alkyl benzene R-CH3 + [O] ——> R-COOH
Hydrolysis of esters RCOOR + H2O RCOOH + ROH
Hydrolysis of acyl chlorides RCOCl + H2O ——> RCOOH + HCl
Hydrolysis of nitriles RCN + 2 H2O ——> RCOOH + NH3
Hydrolysis of amides RCONH2 + H2O ——> RCOOH + NH3

16. CHEMICAL PROPERTIESCHEMICAL PROPERTIES
ACIDITYACIDITY
weak acids RCOOH + H2O(l) RCOO¯(aq) + H3O+
(aq)
form salts RCOOH + NaOH(aq) ——> RCOO¯Na+
(aq) + H2O(l)
2RCOOH + Mg(s) ——> (RCOO¯)2Mg2+
(aq) + H2(g)
The acid can be liberated from its salt by treatment with a stronger acid.
e.g. RCOO¯ Na+
(aq) + HCl(aq) ——> RCOOH + NaCl(aq)
Conversion of an acid to its water soluble salt followed by acidification of
the salt to restore the acid is often used to separate acids from a mixture.
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.

17. ACIDITYACIDITY
• Carboxylic acids are the most acidic organic compounds but are weak
acids compared to HCl and Sulfuric acids.
• Electron withdrawing substituents increase the stability by stabilizing
the carboxylate.

18. ReactivityReactivity
• Carboxyl group show the chemistry of both carbonyl and the hydroxyl groups.
• In most of the reactions, carboxyl group is retained.
• Reactivity of carboxylic acids is due to the presences of carbonyl group.
Types of reactions by Carboxylic acidsTypes of reactions by Carboxylic acids
• Salt Formation ( H- of carboxyl group is involved )
• Replacement of -OH group
• Reactions involving carboxyl group as a whole.

19. CHLORINATION OF CARBOXYLIC ACIDSCHLORINATION OF CARBOXYLIC ACIDS
Chlorination involves replacing the OH with a Cl
Product acyl chloride
Reagent thionyl chloride SOCl2
Conditions DRY conditions
Equation CH3COOH + SOCl2 ——> CH3COCl + SO2 + HCl
Alternative
method CH3COOH + PCl5 ——> CH3COCl + POCl3 + HCl
phosphorus(V) chloride

20. ACYL CHLORIDESACYL CHLORIDES
Structure Replace the OH of a carboxylic acid with a Cl atom
Nomenclature Named from corresponding acid
… remove -ic add -yl chloride
CH3COCl ethanoyl (acetyl) chloride
C6H5COCl benzene carbonyl (benzoyl) chloride
ETHANOYL CHLORIDE

21. ACYL CHLORIDES - PROPERTIESACYL CHLORIDES - PROPERTIES
Physical • polar, colourless liquids which fume in moist air
Chemical • attacked at the positive carbon centre by nucleophiles
such as water, alcohols, ammonia and amines
• undergo addition-elimination reactions
• MUCH MORE REACTIVE THAN…
CARBOXYLIC ACIDS AND ACID ANHYDRIDES
δ
+
δ
−
δ
−

22. ACYL CHLORIDES - REACTIONSACYL CHLORIDES - REACTIONS
WATERWATER
Product(s) carboxylic acid + HCl (fume in moist air /
strong acidic solution formed)
Conditions cold water
Equation CH3COCl(l) + H2O(l) —> CH3COOH(aq) + HCl(aq)
Mechanism addition-elimination
ALCOHOLS
Product(s) ester + hydrogen chloride
Conditions reflux in dry (anhydrous) conditions
Equation CH3COCl(l) + CH3OH(l) —> CH3COOCH3(l) + HCl(g)
Mechanism addition-elimination

23. ACYL CHLORIDES - REACTIONSACYL CHLORIDES - REACTIONS
AMMONIAAMMONIA
Product(s) Amide + hydrogen chloride
Conditions Low temperature and excess ammonia. Vigorous reaction.
Equation CH3COCl(l) + NH3(aq) —> CH3CONH2(s) + HCl(g)
or CH3COCl(l) + 2NH3(aq) —> CH3CONH2(s) + NH4Cl(s)
Mechanism addition-elimination
AMINES
Product(s) N-substituted amide + hydrogen chloride
Conditions anhydrous
Equation CH3COCl(l) + C2H5NH2(aq) —> CH3CONHC2H5(s) + HCl(g)
or CH3COCl(l) + 2C2H5NH2(aq) —> CH3CONHC2H5(l) + C2H5NH3Cl(s)
Mechanism addition-elimination

24. ESTERIFICATIONESTERIFICATION
Reagent(s) alcohol + strong acid catalyst (e.g conc. H2SO4 )
Conditions reflux
Product ester
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
Naming esters Named from the original alcohol and carboxylic acid
CH3OH + CH3COOH CH3COOCH3 + H2O
from ethanoic acid CH3COOCH3 from methanol
METHYL ETHANOATE

25. ESTERSESTERS
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, acyl chlorides and acid anhydrides
Reactivity Unreactive compared with acids and acyl chlorides
Isomerism Esters are structural isomers of carboxylic acids
ETHYL METHANOATEMETHYL ETHANOATE

26. 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
react with alcohols hydrolysed to acids
STRUCTURAL ISOMERISM –STRUCTURAL ISOMERISM – FUNCTIONAL GROUPFUNCTIONAL GROUP

27. PREPARATION OF ESTERS - 1PREPARATION OF ESTERS - 1
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’

28. PREPARATION OF ESTERS - 2PREPARATION OF ESTERS - 2
Reagent(s) alcohol + acyl chloride
Conditions reflux under dry conditons
Equation e.g. CH3OH(l) + CH3COCl(l) ——> CH3COOCH3(l) + HCl(g)
methanol ethanoyl methyl
chloride ethanoate
Notes Acyl chlorides are very reactive
but must be kept dry as they react
with water.

29. PREPARATION OF ESTERS - 3PREPARATION OF ESTERS - 3
Reagent(s) alcohol + acid anhydride
Conditions reflux under dry conditons
Equation e.g. CH3OH(l) + (CH3CO)2O(l) ——> CH3COOCH3(l) + CH3COOH(l)
methanol ethanoic methyl ethanoic
anhydride ethanoate acid
Notes Acid anhydrides are not as reactive as
acyl chlorides so the reaction is slower.
The reaction is safer - it is less exothermic.
Acid anhydrides are less toxic.

30. HYDROLYSIS OF ESTERSHYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
HCOOH + C2H5OH
METHANOIC ETHANOL
ACID
CH3COOH + CH3OH
ETHANOIC METHANOL
ACID
ETHYL METHANOATE
METHYL ETHANOATE

31. HYDROLYSIS OF ESTERSHYDROLYSIS 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 ——> 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

32. USES OF ESTERSUSES OF ESTERS
Despite being fairly chemically unreactive, esters are useful as ...
• flavourings apple 2-methylbutanoate
pear 3-methylbutylethanoate
banana 1-methylbutylethanoate
pineapple butylbutanoate
rum 2-methylpropylpropanoate
• solvents nail varnish remover - ethyl ethanoate
• plasticisers

33. Anhydrides
The functional group of an anhydrideanhydride is two carbonyl groups bonded
to the same oxygen.
◦ The anhydride may be symmetrical (from two identical acyl
groups), or mixed (from two different acyl groups).
◦ To name an anhydride, drop the word "acidacid" from the name of the
carboxylic acid from which the anhydride is derived and add the
word "anhydrideanhydride”.

34. Examples
Formation Of Acid AnhydrideFormation Of Acid Anhydride

35. Hydrolysis of AnhydridesHydrolysis of Anhydrides
HydrolysisHydrolysis is a chemical decomposition involving breaking a bond and
the addition of the elements of water.
• Carboxylic anhydrides, particularly the low-molecular- weight ones,
react readily with water (hydrolyze) to give two carboxylic acids.

36. AmidesAmides

37. Preparation of AmidesPreparation of Amides
• In principle, we can form an amide by treating a carboxylic acid with an
amine and removing -OH from the acid and an -H from the amine.
• In practice what occurs if the two are mixed is an acid-base reaction
to form an ammonium salt.
• If this salt is heated to a high enough temperature, water is
eliminated and an amide forms.

38. Preparation of AmidesPreparation of Amides
• It is much more common, however, to prepare amides by treating an
amine with an anhydride.

39. Hydrolysis of AmidesHydrolysis of Amides
Amides require more vigorous conditions for hydrolysis in both acid
and base than do esters.
• Hydrolysis in hot aqueous acid gives a carboxylic acid and an
ammonium ion.
• Hydrolysis is driven to completion by the acid-base reaction
between ammonia or the amine and the acid to form an ammonium
ion.
• Each mole of amide hydrolyzed requires one mole of acid.

40. THETHE
ENDEND
AN INTRODUCTION TOAN INTRODUCTION TO
CARBOXYLIC ACIDSCARBOXYLIC ACIDS
AND THEIR DERIVATIVESAND THEIR DERIVATIVES