1. CARBOXYLIC ACID AND ITS DERIVATIVES

2. Structure
RCOOH or RCO2H
(R ≡ alkyl, aryl or H)

3. NOMENCLATURE

4. IUPAC Nomenclature & Common Name
HCOOH
Methanoic acid
Formic acid
CH3COOH
Ethanoic acid
Acetic acid
CH3CH2COOH
Propanoic acid
Propionic acid
CH3CH2CH2COOH
Butanoic acid
Butyric acid
CH3CH2CH2CH2COOH
Pentanoic acid
Valeric acid

5. IUPAC Nomenclature The longest chain must contain the carboxyl group.
The carboxyl group is at the terminal, therefore the carbon of the carboxyl group is not numbered.
One COOH – carboxyl group is at one end
Two COOH – carboxyl groups are at both ends
Name the compound as alkane, drop ‘e’ in alkane and add ‘oic acid’ (eg: methanoic acid)

6. 4-bromo-3-methylpentanoic acid2
4-bromo-3-methylpentanoic acid C H 2 O 3
5-hydroxyhexanoic acid
5-methyl-3-hexenoic acid

7. Two COOH groups, the compound will be named as alkanedioic acid’ (Example: ethanedioic acid, propanedioic acid and etc)
pentanedioic acid

8. 3-methylhexanedioic acid
trans 3-hexenedioic acid

9. When R is an aryl group, the parent name is benzoic acid
4-chlorobenzoic acid

10. An aromatic dicarboxylic acid is named as 1,x-benzenedicarboxylic acid
2-isopropyl-1,4-benzenedicarboxylic acid

11. A cyclic carboxylic acid is named as cycloalkanecarboxylic acid
The C atom which is attached to —COOH is numbered as C1 1
cyclopentanecarboxylic acid

12. cyclohexanecarboxylic acid1
4-bromo-2-methylcyclohexanecarboxylic acid 1

13. A cyclic dicarboxylic acid is named as 1,x-cycloalkanedicarboxylic acid
1,2-cyclohexanedicarboxylic acid
4-chloro-1,2-cyclohexanedicarboxylic acid

14. When a compound contains a carboxyl group and other functional group(s), the priority is given to the carboxylic acid as the parent name.
3-methyl-2-cyclohexenecarboxylic acid

15. PHYSICAL PROPERTIES OF CARBOXYLIC ACIDS

16. Boiling Point
The boiling point of carboxylic acid is higher than an alcohol, a ketone or an aldehyde (with Mr that almost the same) because:
it exists as stable dimers that form hydrogen bond.
molecules in dimers are arranged closely packed, therefore the hydrogen bonds are relatively strong.
high energy is needed to overcome the intermolecular forces ,
 boiling point 

17. Hydrogen bond
Hydrogen bond

18. Solubility a) Solubility in water
Carboxylic acids are soluble in water due to the formation of hydrogen bond between the water molecules and carboxylic acid molecules.
Hydrogen Bonds

19. The solubility of carboxylic acid in water is almost the same as alcohol.
Aliphatic carboxylic acids with C > 5 are insoluble in water. Size of R ↑, hydrophobic area ↑.
hydrophilic
hydrophobic

20. Aromatic carboxylic acids are slightly soluble in water due to the huge aromatic ring.
Dicarboxylic acids are relatively more soluble since more hydrogen bonds are formed.

21. Example : Descending order of solubility
>
>
>

22. b. Solubility in non polar solvent
Carboxylic acids are soluble in non polar solvent such as benzene due to the Van der Waals forces between the benzene and alkyl group of carboxylic acids .
Van der Waals forces
Van der Waals forces
Hydrogen bonds

23. Acidity of Carboxylic Acid
The acidity of carboxylic acid is influenced by:
Resonance effect
Inductive effect

24. Resonance Effect
Carboxylate ion :
Phenoxide ion :

25. Carboxylic acids are more acidic due to the resonance stabilisation of the carboxylate ion.
The electrons in carboxylate ion are delocalised between two oxygen atoms, whereas in phenoxide ion, the electrons are delocalized in the benzene ring.
The C=O group in carboxylic acid is a electron-withdrawing group which reduce the electron density of –OH, therefore the –OH bond becomes weaker.
Thus H+ is easily donated and carboxylic acid is more acidic than phenol.

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

27. (resonance structure) (resonance structure)
+ H2O
+ H3O+
carboxylate ion
(resonance structure) ⇌
carboxylic acid
+ H3O+ ⇌
phenoxide ion
(resonance structure)
+ H2O
phenol
R—O—H + H2O ⇌ R—O– H3O+
alkoxide ion
alcohol

28. Inductive Effect
An electron withdrawing group (deactivating group) that attached to a carboxylate ion will delocalise the negative charge, thereby stabilises the carboxylate ion and increases acidity.
An electron donating group, (activating group) will destabilise the carboxylate ion and decreases acidity.

29. The inductive effect electron-withdrawing group in the compound
electron-withdrawing groups
(e.g –NO2 ,-F,-Cl,-Br, -I ) reduce the electron density of
–O H.
Thus the O-H bond becomes weaker and H+ can be easily released.
The compound is said to be more acidic
 Electron- withdrawing group increases the acidity.

30. Example:
CH3CHCl-COOH and CH3CH2COOH
Cl is an electron-withdrawing groups, therefore reduce the electron density of –OH.
Thus the O-H bond becomes weaker and H+ can be easily released.
Acidity :
CH3CHCl-COOH > CH3CH2COOH
Electron-withdrawing groups increase the acidity.

31. ii) The electronegativity of electron-withdrawing group in the compound
Example:
CH3CHF-COOH and CH3CHCl-COOH
Both F and Cl are electron-attracting group.
The electronegativity of F > Cl
The electron density of –OH in CH3CHF-COOH is less, thus the –OH bond is weaker than in
CH3CHCl-COOH. Therefore, H+ is easily donated.
Acidity : CH3CHF-COOH > CH3CHCl-COOH

32. iii) Number of electron-attracting group in the compound.
Example:
CH3C(Cl)2-COOH and CH3CHCl-COOH
CH3C(Cl)2-COOH contains 2 Cl atoms that make the bond of –OH weaker than CH3CHCl-COOH (with only one Cl atom). Thus, H+ is easily donated.
Acidity : CH3C(Cl)2-COOH > CH3CHCl-COOH

33. iv) The position of electron-attracting group
Example:
CH3CH2CH(Cl)COOH and CH2(Cl)CH2CH2COOH
The distance between Cl atom and carboxyl group in CH3CH2CHCl-COOH is nearer compare to in CH2ClCH2CH2-COOH.
The –OH bond in CH3CH2CH(Cl)COOH is weaker than in CH2ClCH2CH2-COOH, so H+ is easily donated.
Acidity :
CH3CH2CH(Cl)COOH > CH2(Cl)CH2CH2COOH

34. (v ) The inductive effect of electron- releasing (electron-donating) group in the compound
Example:
CH3COOH and CH3CH2COOH
-R is an electron –releasing group.
The size of –R group in CH3CH2COOH is larger than in CH3COOH, so CH3CH2- is a stronger releasing group than CH3-.
The electron density of –OH in CH3CH2COOH increases and H+ is difficult to be donated.
 Electron-releasing groups reduce the acidity of a carboxylic acid.

35. SYNTHESIS OF CARBOXYLIC ACIDS

36. 1. Oxidation of primary alcohol and aldehyde
oxidizing
agent
oxidizing
agent
1o alcohol
aldehyde
carboxylic acid
Common oxidizing agents are :
KMnO4 / H2SO4
potassium permanganate
Na2Cr2O7 /H2SO4
potassium /sodium dichromat (VI)

37. 2. Oxidation of Alkyl Benzene
oxidizing
agent
KMnO4 , H+ Δ
+ CO2 + H2O

38. 3. Formation and Hydrolysis of nitrile
NaCN
H2O,H+
H2O,H+
NaCN

39. 4. Carbonation of Grignard Reagents
R—MgX
R—COOH
+ Mg(OH)X
H2O, H+
CO2
H2O, H+
+ Mg(OH)Br

40. CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS

41. Main reactions of carboxylic acid,
The reaction that involves the donation of H+ from –OH group.
The reaction that involves the substitution of OH group
The reaction that involves the reduction with LiAlH4 to primary alcohol

42. The reaction that involves the donation of H+ from –OH group
1. Neutralisation
Carboxylic acids are acidic, it can react with base such as NaOH (aq) to give metal carboxylate salts,
+ NaOH
+ H2O
Na+

43. – Na+
+ NaOH
+ H2O
Sodium benzoate

44. 2. Reaction with electropositive metals such as Na, K, Ca, Mg and Fe.
Exercise:

45. The reaction that involves the substitution of –OH group (to form its derivatives)
1. Acid chloride formation
Acid chloride can be prepared from the reaction of carboxylic acids with thionyl chloride, SOCl2 ; phosphorous pentachloride, PCl5 ; phosphorous trichloride, PCl3
SOCl2
+ SO2 + HCl
PCl5
+ POCl3 + HCl
PCl3
+ H3PO3

46. Exercise :
SOCl2
PCl5
PCl3

47. 2. Esterification
Carboxylic acids react with alcohols in the presence of mineral
acid catalyst to produce esters. H+ ⇌
+ H—OR’
+ H2O
carboxylic acid
alcohol
ester H+
+ HOCH2CH3 ⇌
propanoic acid
ethanol
ethyl propanoate
+ H2O

48. 3. Acid anhydride formation
Acid anhydrides can be prepared from carboxylic acids by
the loss of water through heating. +
heat
+ H2O
acid anhydride
heat +
ethanoic anhydride
+ H2O

49. Reaction of carboxylic acids with an ammonia or amine give amide.
4. Amides formation
Reaction of carboxylic acids with an
ammonia or amine give amide.
NH3
+ H2O
1o amide
RNH2
+ H2O
(1o amine)
2o amide
R2NH
+ H2O
(2o amine)
(3o amide)

50. Exercise :
NH3

51. The reaction that involves the reduction with LiAlH4 to primary alcohol
Carboxylic acid are reduced to primary alcohols by reaction with lithium aluminium hydride, LiAlH4 .
LiAlH4
ether
+ R’OH
1o alcohol
LiAlH4
ether
+ HO—CH2CH3

52. Methanoic acid, HCOOH as a reducing agent
Methanoic acid molecule, has both
and
carbonyl
carboxylic
It shows the properties of both carboxylic acid and aldehyde.
It also shows reducing properties in reactions with acidified
KMnO4 or K2Cr2O7 and Tollens’ reagent.

53. KMnO4 / H+
CO2 + H2O + MnO2
(Brown)
Ag(NH3)2+
Ag + CO2 + H2O

54. DERIVATIVES OF CARBOXYLIC ACIDS

55. Reactions of carboxylic acid derivatives
i. Hydrolysis of acid chlorides
H2O
+ HCl
acid chloride
carboxylic acid
ii. Hydrolysis of acid anhydrides
H2O 2
acid
anhydride
carboxylic acid

56. Reactions of carboxylic acid derivatives
iii. Hydrolysis of esters
H2O H+
carboxylic acid
+ ROH
NaOH
alcohol
Na+
ester

57. Example :
H2O
benzoyl chloride
H2O
ethanoic anhydride

58. Example :
H2O H+
methyl ethanoate

59. Relative Reactivity Of Carboxylic Acid Derivatives
The reactivity of a carboxylic acid derivative depends
on the basicity of the substituent (leaving group) that attached to the acyl group
The less basic the substituent, the more reactive the carboxylic acid derivative.

60. Relative basicities of the leaving group (substituent)
Cl– < RCOO– < RO– < HO– < NH2– ,
acid
chloride
acid
anhydride
ester
carboxylic
acid
amide
reactivity increases

61. ACYL CHLORIDE
Acyl chloride is the most reactive because of its electropositive carbonyl group is attach to the electronegative Cl atom (which is a releasing group).

62. ANHYDRIDE ACID
Anhydride acid is more reactive than ester and amide because the carboxyl group of anhydride is attached to the carbonyl carbon.
This makes the carbonyl carbon becomes more electropositive and can be easily attack by nucleophile.

63. ESTER
Ester is less reactive towards nucleophile because the delocalization of electron makes the positive charge of carbon can be shifted to oxygen.
That makes the carbonyl carbon less electropositive.

64. AMIDE
Amide is the least reactive because, NH2 group is an electron-donating group that makes the carbonyl less electropositive.
The resonance structure of amide shows that the carbonyl carbon is not electropositive.

65. The Uses of Carboxylic Acid
Carboxylic acid / derivatives
Uses
Polyamide (Nylon)
carpet, apparel
Ester
Artificial flavors
Acetic acid
Vinegar
Ethanoic anhydride
Drug aspirin
Salicylic acid
analgesic