1. KNOCKHARDY PUBLISHING
AN INTRODUCTION TO
CARBOXYLIC ACIDS AND THEIR DERIVATIVES
KNOCKHARDY PUBLISHING

2. KNOCKHARDY PUBLISHING
CARBOXYLIC ACIDS
INTRODUCTION
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3. CARBOXYLIC ACIDS CONTENTS Structure of carboxylic acids Nomenclature
Physical properties of carboxylic acids
Preparation of carboxylic acids
Chemical properties of carboxylic acids
Esters
Acyl chlorides
Revision check list

4. Before you start it would be helpful to…
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

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

6. STRUCTURE 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

7. STRUCTURE 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’

8. Carboxylic acids form a homologous series
HCOOH CH3COOH C2H5COOH

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

10. INFRA-RED SPECTROSCOPY
IDENTIFYING CARBOXYLIC ACIDS USING INFRA RED SPECTROSCOPY
Differentiation Compound O-H C=O
ALCOHOL YES NO
CARBOXYLIC ACID YES YES
ESTER NO YES
ALCOHOL CARBOXYLIC ACID ESTER
O-H absorption O-H + C=O absorption C=O absorption

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
e.g. CH3 - CH(CH3) - CH2 - CH2 - COOH is called 4-methylpentanoic acid

12. 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

13. 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

14. 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

15. Increases as size increases - due to increased van der Waals forces
PHYSICAL PROPERTIES
BOILING POINT
Increases as size increases - due to increased van der Waals forces
101°C °C °C °C

16. PHYSICAL PROPERTIES BOILING POINT
Increases as size increases - due to increased van der Waals forces
101°C °C °C °C
Boiling point is higher for “straight” chain isomers.
164°C °C
Greater branching = lower inter-molecular forces = lower boiling point

17. 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
propan-1-ol C3H7OH h-bonding
propanal C2H5CHO dipole-dipole
butane C4H basic V der W

18. 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 O—H bonds
AN EXTREME CASE... DIMERISATION
• extra inter-molecular attraction = more energy to separate molecules
HYDROGEN BONDING

19. PHYSICAL PROPERTIES SOLUBILITY
• carboxylic acids are soluble in organic solvents
• they are also soluble in water due to hydrogen bonding
HYDROGEN BONDING

20. 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
HYDROGEN BONDING

21. PREPARATION OF CARBOXYLIC ACIDS
Oxidation of aldehydes RCHO [O] ——> RCOOH
Hydrolysis of esters RCOOR + H2O RCOOH ROH
Hydrolysis of acyl chlorides RCOCl H2O ——> RCOOH HCl
Hydrolysis of nitriles RCN H2O ——> RCOOH NH3
Hydrolysis of amides RCONH H2O ——> RCOOH NH3

22. CHEMICAL PROPERTIES ACIDITY
weak acids RCOOH + H2O(l) RCOO¯(aq) H3O+(aq)
form salts RCOOH NaOH(aq) ——> RCOO¯Na+(aq) H2O(l)

23. CHEMICAL PROPERTIES ACIDITY
weak acids RCOOH + H2O(l) RCOO¯(aq) H3O+(aq)
form salts RCOOH NaOH(aq) ——> RCOO¯Na+(aq) H2O(l)
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.

24. CHEMICAL PROPERTIES ACIDITY
weak acids RCOOH + H2O(l) RCOO¯(aq) H3O+(aq)
form salts RCOOH NaOH(aq) ——> RCOO¯Na+(aq) H2O(l)
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

25. ESTERIFICATION
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

26. ESTERIFICATION
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

27. ESTERIFICATION
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 CH3COOCH H2O
from ethanoic acid CH3COOCH3 from methanol
METHYL ETHANOATE

28. CHLORINATION 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 SO HCl

29. 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

30. 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 Unreactive compared with acids and acyl chlorides
METHYL ETHANOATE
ETHYL METHANOATE

31. 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 Unreactive compared with acids and acyl chlorides
Isomerism Esters are structural isomers of carboxylic acids
METHYL ETHANOATE
ETHYL METHANOATE

32. 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

33. PREPARATION 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’

34. PREPARATION 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

35. PREPARATION 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 the reaction is slower.
The reaction is safer - it is less exothermic.
Acid anhydrides are less toxic.

36. Hydrolysis is the opposite of esterification
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
HCOOH C2H5OH
METHANOIC ETHANOL
ACID
ETHYL METHANOATE

37. Hydrolysis is the opposite of esterification
HYDROLYSIS OF ESTERS
Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
HCOOH C2H5OH
METHANOIC ETHANOL
ACID
ETHYL METHANOATE
METHYL ETHANOATE

38. Hydrolysis is the opposite of esterification
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

39. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
The products of hydrolysis depend on the conditions used...
acidic CH3COOCH H2O CH3COOH CH3OH
alkaline CH3COOCH NaOH ——> CH3COO¯ Na CH3OH

40. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
The products of hydrolysis depend on the conditions used...
acidic CH3COOCH H2O CH3COOH CH3OH
alkaline CH3COOCH NaOH ——> CH3COO¯ Na CH3OH
If the hydrolysis takes place under alkaline conditions,
the organic product is a water soluble ionic salt

41. HYDROLYSIS OF ESTERS Hydrolysis is the opposite of esterification
ESTER + WATER CARBOXYLIC ACID + ALCOHOL
The products of hydrolysis depend on the conditions used...
acidic CH3COOCH H2O CH3COOH CH3OH
alkaline CH3COOCH 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

42. 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)
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
CH2OH
CHOH

43. USES 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

44. ACYL CHLORIDES
Nomenclature Named from the corresponding carboxylic acid
remove -ic add -yl chloride
CH3COCl ethanoyl chloride
C6H5COCl benzene carbonyl (benzoyl) chloride
Chemical
Properties • 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

45. ACYL CHLORIDES Reagent Water Product(s) carboxylic acid + HCl
(fume in moist air / strong acidic solution formed)
Conditions room temperature
Equation CH3COCl(l) H2O(l) ——> CH3COOH(aq) + HCl(aq)
Mechanism addition-elimination

46. ACYL CHLORIDES Reagent Alcohols Product(s) ester + hydrogen chloride
Conditions reflux in dry (anhydrous) conditions
Equation CH3COCl(l) CH3OH(l) ——> CH3COOCH3(l) + HCl(g)
Mechanism addition-elimination

47. ACYL CHLORIDES Reagent Ammonia 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) NH3(aq) ——> CH3CONH2(s) + NH4Cl(s)
Mechanism addition-elimination

48. ACYL CHLORIDES Reagent Amines
Product(s) N-substituted amide + hydrogen chloride
Conditions anhydrous
Equation CH3COCl + C2H5NH2 ——> CH3CONHC2H5 + HCl
or CH3COCl + 2C2H5NH2 ——> CH3CONHC2H5 + C2H5NH3Cl
Mechanism addition-elimination - similar to that with ammonia.

49. What should you be able to do?
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.
CAN YOU DO ALL OF THESE? YES NO

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52. © JONATHAN HOPTON & KNOCKHARDY PUBLISHING
AN INTRODUCTION TO
CARBOXYLIC ACIDS AND THEIR DERIVATIVES
THE END
© JONATHAN HOPTON & KNOCKHARDY PUBLISHING