2. 01 02 03 04 05
Learning Outcomes
At the end of session students should able to-
Describe
Carboxylic acids
Interconvert
Carboxylic acids
to amides and
esters
Compare acidity
of substituted
Carboxylic acids
Know and explain
functional group
test for
Carboxylic acids
Draw structure
and list out
various uses of
Carboxylic acid
compounds
3. 1 Definition
When aromatic ring is present in place of alkyl
group it becomes aromatic carboxylic acid. Ar-COOH
O
R C
OH
Organic compound which contains carboxyl group (- COOH )
are called carboxylic acid.
General formula R-COOH or Where R is alkyl group
4. On the basis of numbers of -COOH group present as-
1. Monocarboxylic acid- Acetic acid
2. Dicarboxylic acid- Oxalic Acid
3. Tricarboxylic acid- Citric Acid
4. Fatty Acid- long chain of monocarboxylic acid is called as fatty acid
01 Classification
O
H C C3
OH
H2C COOH
H2C COOH
H2C COOH
HC COOH
H2C COOH
5. 01 Acidity of carboxylic acid
• Carboxylic acid are acidic in nature because they can donate
proton form COOH group and form salt with base.
• They are weak acid.
OO
+ +NaOH H2OR CR C
- +
O NaOH
Base SaltCarboxylic acid
6. 01 Stability of Carboxylate ion
Carboxylic acids dissociate in water to form carboxylate ion and
hydronium ion. The carboxylate ion formed is stabilized
through resonance by effective delocalization of the negative
charge.
7. 01 Effect of substituent on acidity
Inductive effect: Inductive effect means polarity produces in
molecule as result of higher electronegativity of one atom compared
to another.
+I effect- If atom or groups lose/donate electron towards carbon is
said to have +I effect. Example- CH3, C2H5, 3⁰, 2⁰, 1⁰ alkyl group,
COO-
-I effect- If atom or groups which draw electron away from carbon is
said to have -I effect. Example- Cl, Br, I, F, OH, NH2, CN
8. 02 Effect of substituent on acidity
Effect of Electron releasing alkyl group (H, CH3, CH2CH3) on acidity
• This can be explained with the help of inductive effect of substituent
on alpha carbon atom
• Electron releasing alkyl group decreases the acidity
• Reason is that, electron releasing group increases the negative
charge on the carboxylate ion and destabilize it.
• The loss of proton becomes more difficult.
• As the size of alkyl group increase acidity decreases
9. 03
Formic acid more stronger than acetic acid and propionic acid?
O OO
H3C C H5C2 CH C
OH OHOH
Formic acid
pKa- 3.75
Acetic acid
pKa- 4.76
Propionic
pKa- 4.87
acid
Decreasing strength as pKa value increases
Effect of substituent on acidity
10. 04 Effect of substituent on acidity
Effect of Electron withdrawing group (Cl, Br, F, OH, CN) on
acidity
Electron withdrawing group increases the acidity
• Reason is electronegativity of halogen, as the
electronegativity increases inductive effect increases.
Therefore less negative charge on the carboxylate ion help to
stabilize it.
• The loss of proton becomes more easy.
11. 05
Effect of Electron withdrawing group (Cl, Br, F, OH, CN) on acidity
Effect of substituent on acidity
CH3-COOH
Acetic acid
4.76
Br-CH2-COOH
Bromo acetic acid
2.90
Cl-CH2-COOH
Chloro acetic acid
2.86
F-CH2-COOH
Fluro acetic acid
2.59
Increasing strength as pKa value decreases
12. 06 Effect of substituent on acidity
Multiple halogen substitution increases the acidity
CH3-COOH
Acetic acid
Cl-CH2-COOH
Mono Chloro
acetic acid
2.86
Cl2-CH-COOH
Di Chloro acetic
acid
1.48
Cl3-C-COOH
Tri Chloro acetic
acid
0.704.76
Increasing strength as pKa value decreases
13. 07 Effect of substituent on acidity
Benzoic acid Versus Acetic acid
As you can see, in benzoic acid benzene ring is present which is an electron-
withdrawing group and hence it makes the 0-H bond more polar and easier to
break. This makes benzoic acid more acidic. While, there is no electron-
withdrawing group in ethanoic acid. Therefore, benzoic acid is more acidic than
ethanoic acid.
Vs
14. 01 Qualitative test: Carboxylic acid
1. Sodium bicarbonate (NaHCO3) test:
Present
Test Observation Inference
Compound + 2-3 ml
of saturated Sod.
Bicarbonate solution
Effervescence of CO2
COOH group
15. 02
2. Ester test:
Test Observation Inference
Compound + 2-3 ml
ethanol + 2 drops of
Conc. Sulphuric acid
and heat
Sweet or Fruity
Smell
COOH group
Present
OO
+ +C2H5OH H2OR CR C
OC2H5
Ester (Sweet smell)
OH
EthanolCarboxylic acid
Qualitative test: Carboxylic acid
16. 03
3. Neutral solution test: (CaCl2)
Qualitative test: Carboxylic acid
Test Observation Inference
Prepare neutral solution of acid as- 0.2 g acid substance + 2ml NH4OH, boil till
ammonia gets evolved (litmus test & Moist turmeric paper should not turn brown)
Neutral solution of
acid sub+ 2-3 drops
of CaCl2
a) White ppt. insoluble in dil. Acetic
acid but soluble in dil. HCl
b) White ppt. on boiling. Soluble in
dil. Acetic acid.
c) White ppt. insoluble in dil. Acetic
acid.
Oxalic acid (MP. 101°C)
Succinic acid(MP. 185°C)
Cinnamic acid(MP. 133°C)
17. 04
4. Neutral solution test (FeCl3)
Qualitative test: Carboxylic acid
Aspirin (MP.135°C)
Cinnamic acid (MP.133°C)
213°C)
n-Butyric acid (BP.163°C)
Prepare neutral solution of acid as- 0.2 g acid substance + 2ml NH4OH, boil till
ammonia gets evolved (litmus test & Moist turmeric paper should not turn brown)
Neutral solution of
acid sub.+ 2-3 drops
of FeCl3
a) Voilet colour disappeared by
dilute HCl
b) buff or brown ppt. soluble in
dilute HCl
c) Red colour soluble in dilute HCl
Salicylic acid (MP.158°C)
Benzoic Acid (MP.122°C)
Pthalic acid (MP.193-
Succinic acid (MP.185°C)
Acetic acid (BP.118°C)
18. 01
1. Alkaline hydrolysis:
Qualitative test: Ester
R-CO-OR’
Test Observation Inference
Substance + 2 ml water +
2 drops of
Phenolphthalein + very
dilute NaOH, drop by
drop till pink colour
persist then heat the
solution
Pink colour disappears
on heating
Ester Group Present
OO
Heat
+
OC2H5
+NaOH C2H5-OHR CR C alkaline hydrolysis
ONa
EthanolSalts of acidEster
19. 02
2. Hydroxamic acid test
Qualitative test: Ester
R-CO-OR’
Test Observation Inference
Substance + 1 ml
Hydroxylamine
hydrochloride + 10% NaOH
heat to boil. Cool this and
add dilute HCl till neutral.
Add 1-2 drops of aqueous
FeCl3
Red-violet colour appear
Ester Group Present
20. 01 Qualitative test: Amide
1. Base Hydrolysis test
R-CO-NH
Test Observation Inference
Substance + 3 ml 10%
NaOH and boil
Evolution of NH3 gas;
tested by turmeric paper
(turns red brown)
Amide Group Present
2
OO
Heat
+ +NaOH NH3R CR C alkaline hydrolysis
ONaNH2
AmmoniaSalts of acidAmide
21. 02 Qualitative test: Amide
2. Hydroxamic acid test:
R-CO-NH2
Test Observation Inference
Substance + 1 ml
Hydroxylamine
hydrochloride + 10% NaOH
heat to boil. Cool this and
add dilute HCl till neutral.
Add 1-2 drops of aqueous
FeCl3
Blue-red colour
Amide Group Present
22. 03
3. Biuret test:
Qualitative test: Amide
R-CO-NH2
Test Observation Inference
Heat 0.2 g substance indry
test tube till evolution of
NH3 ceases. Dissolve the
remaining solid in 2 ml
dilute NaOH & add 1-2 ml
dilute cooper sulhate
solution drop wise.
Formation violet colour
Amide Group Present
23. 04
4. Nitrous acid test
Qualitative test: Amide
R-CO-NH2
Test Observation Inference
0.2 g substance heat in test
tube + 2 ml dilute HCl + 2
ml NaNO2 solution and boil
off N2 from above test
Brisk effervescence due to
N2
Clear solution
White ppt
Amide Group Present
Aliphatic amide
Aromatic amide
OO
++ + H2OHNO2 N2R CR C
OHNH2
acidAmide
24. 01 Structure and Uses
1. Acetic Acid
1. 3-5% acetic acid is vinegar used as food additive
2. As aprotic solvent in organic reaction-Friedel-Craft reaction
3. In manufacture of dye, rubber, plastics
4. In film industry
5. For blood testing in clinical laboratory
6. 1% solution as antiseptic
7. Ester of acetic acid are used in making ink, paint, coating.
IUPAC: Ethanoic acid
25. 02 Structure and Uses
2.Lactic Acid
1. t is main component of lactate ringer solution
2. Commonly used fluid in trauma, surgery, burn
3. Used as a food additive
4. In making detergent
5. Lactic acid cream used to treat dry, itchy, scaly skin
6. Antibacterial agent
IUPAC: 2-Hydroxypropanoic acid
COOH
H3C OH
H
26. 03 Structure and Uses
3. Tartaric acid
1. Food additive in gel, jellies, candy as a preservative
2. In production of effervescent tablet
3. Used in baking powder
4. Chelating agent in foam and metal industry
5. As antioxidant in variety of food product
6. For making silver mirror, tanning of leather
7. For making blue prints
IUPAC: 2,3-Dihydroxybutanedioic acid.
COOH
H
HO
C OH
H
C
COOH
27. 04 Structure and Uses
4. Citric Acid
1. Used in effervescent formulae
2. Flavouring agent and preservative in food and beverages
3. It is excellent chelating agent
4. In preparation of cream, gels and liquids
5. Sodium citrate is a component of Benedict’s reagent
6. It is intermediate of TCA cycle
IUPAC: 2-Hydroxypropane-1,2,3-tricarboxylic acid
28. 05 Structure and Uses
5. Succinic acid
1. Acidity regulator in food and beverage industry
2. Flavouring agent
3. As excipient in pharmaceutical product
4. As anti-inflammatory agent to treat arthritis
5. Used to make resins and coating material
6. In manufacturing of dyes and adhesive
IUPAC: 1,4-Butanedioic acidCOOH
H
H
C H
HC
COOH
29. 06 Structure and Uses
6. Oxalic Acid
1. Used for cleaning or bleaching
2. As mordent in dying process
3. Important reagent in lanthanide chemistry
4. Effectively remove ink, food stains
5. As a grinding agent for polishing marble
6. In developing photographic film
IUPAC: Ethanedioic acid
H2C COOH
H2C COOH
30. 07 Structure and Uses
7. Salicylic Acid
1. It is precursor for making aspirin
2. Used in topical medicine to treat psoriasis, dandruff, acne
3. As anti-bacterial and antiseptic
4. Used to remove corns
5. It is prodrug of aspirin
IUPAC: 2-Hydroxybenzoic acid
COOH
OH
31. 08 Structure and Uses
8. Benzoic Acid
1. It is constituent of Whitefield ointment for treatment of fungal
infection
2. Effective food preservative
3. It is precursor for the industrial synthesis of many organic
substance
4. Used in mouthwash, toothpaste, lipstick
5. As antiseptic
IUPAC: Benzoic acid
COOH
32. 09 Structure and Uses
9. Benzyl Benzoate
1. Effective in topical treatment of human scabies
2. To kill lice
3. As mosquito repellent
4. It is a part of asthma and whooping cough drop
5. As a plasticizer
6. As a solvent for cellulose derivative
IUPAC: Benzyl Benzoate
33. 10 Structure and Uses
10. Dimethyl Phthalate
1. As a insect repellent
2. Used as a plasticizer
3. To make flexible plastic like toothbrush
4. In cosmetic
5. In manufacturing of perfume
IUPAC: Dimethyl benzene-1,2-dicarboxylate
COOCH 3
COOCH 3
34. 11 Structure and Uses
11. Methyl salicylate
1. As topical rubefacient and analgesic
2. In low concentration as a flavouring agent in chewing gum
3. As antiseptic in mouthwash
4. It has counterirritant action, works on skin by feeling cool and
then warm
5. To treat minor pain in joint/muscle
IUPAC: Methyl 2-hydroxybenzoateCOOCH 3
OH
35. 12 Structure and Uses
12. Acetyl salicylic acid
(ASPIRIN)
1. As antipyretic and analgesic
2. As anti-clotting agent to reduce risk of heart attack
3. As anti-inflammatory agent for rheumatoid arthritis
IUPAC: 2-Acetoxybenzoic acidCOOH
COOCH 3
