Salicylic acid is obtained from the bark of willow trees. It has the formula C7H6O3 and is a colorless crystalline organic acid. It was first discovered in 1839 by fusing salicylic aldehyde with potassium hydroxide. Salicylic acid is used externally to treat skin conditions like athlete's foot and warts, and is also used in acne treatments. It is synthesized commercially via the Kolbe-Lautemann process, which involves reacting phenol with sodium and carbon dioxide to produce sodium salicylate, then converting it to salicylic acid.

1. Introduction and Preparation
of Salicylic Acid
Guided By:- By:-
Shibu.G.Pillai 13BCH012
(Asst. Professor) 13BCH013

2. SALICYLIC ACID
(C7H6O3)
It is obtained from the bark of the willow tree which
is the substance used to be obtained is
a monohydrobenzoic acid, a type of phenolic acid
and a betahydroxy acid. It has the formula C7H6O3.
This colourless crystalline organic acid is widely
used in organic synthesis and functions as a plant
hormone. It is derived from the metabolism
of salicin.
COOH
OH

3. The acid was first discovered by H. Piria in
1839, by fusing salicylic aldehyde with
potassium hydroxide.

4. Salicylic Acid is used externally on the skin.
It helps in the treatment of athlete’s foot,
ringworm of the scalp, and the removal of
warts, corns, and calluses. Salicylic acid is
also incorporated into preparations for the
treatment of acne, dandruff, seborrhea, and
insect bites

5. Molecula
r wt.
• 138.12 g/mol
Physical
State
• White crystalline solid
Boiling
and
Melting
point
• B.P-211ºC
• M.P-159ºC
• 1.44Specific
Gravity
Slightly soluble in water but
soluble in organic solventsSpecific
Gravity

6. Autoignitio
n and
Flash point
• Auto-ignition-570ºC
• Flash Point-157ºC
pH
• 2.4
Stability
• Stable under ordinary conditions
but sensitive to light

8. Major Manufacturers of
Salicylic Acid in India
 All India Drugs Supply Co.
 Alliance Global-Mumbai
 Hindustan Chemicals and
Pharmaceuticals.
 Forbes Pharmaceuticals.
 Triveni Chemicals-Vapi,Gujarat
 Samrat enterprise-Ahmedabad

9. Methods of Preparation
 By oxidation of or by fusion with
potassium hydroxide, or by electrolysis of
one of the following substances:- salicin,
salicaldehyde, and saligenin.
 By heating with water ortho-diazo
amidobenzoic acid.
 By heating phenol with carbon
tetrachloride and alcoholic potash.

10.  By electrolysis of a solution of benzoic
acid in acetic acid.
 By exposing a solution of benzoic acid to
the sunlight in the presence of a ferric salt.
 From Methyl Salicylate in presence of
Sodium Hydroxide and Sulphuric acid.
 By passing dry carbon dioxide into a hot
mixture of phenol and sodium.(Kolbe and
Lautemann reaction)

11. Kolbe-Lautemann’s Process
for synthesis of Salicylic
Acid.(Commercial Process)
1. Phenol and sodium hydroxide form sodium phenoxide.
C6H5OH + NaOH C6H5ONa + H2O
2. Carbon dioxide when added to the sodium phenoxide forms
sodium phenyl carbonate:
C6H5ONa + CO2 C6H5OCOONa
This stage is completed then the mass is heated to about
110°C for one hour and at about 6 atmosphere.

12. 3. The sodium phenylcarbonate is transformed into sodium
salicylate:
C6H5OCO2Na C6H4OHCOONa
The CO2 goes into the Ortho-position between the
hydrogen atom and the nucleus, producing a carboxyl
group.
4. In the last stage the salt acts with some unchanged sodium
phenate and sets free the Phenol in the disodium salt.
C6H4OHCOONa + C6H5ONa C6H5ONaCOONa +
C6H5OH

13. Mechanism

14. Process Flow Diagram for Kolbe’s
Synthesis

15. From Methyl Salicylate

16. Mechanism