Chapter 20 Carboxylic Acids and their derivatives Part 3- Chemistry free study material by TEACHING CARE online tuition and coaching classes

Chapter 20 Carboxylic Acids and their derivatives Part 3- Chemistry free study material by TEACHING CARE online tuition and coaching classes

File name : Chapter-20-Carboxylic-Acids-and-their-derivatives-Part-3.pdf

 

 

 

 

 

Salicylic acid [O-Hydroxy benzoic acid];

OH

COOH

 

 

Salicylic acid is present in many essential oils in the form of esters. Oil of winter green is a methyl ester of salicylic acid.

(1)  Methods of preparation

  • Kolbe Schmidt reaction

 

 

ONa

 

CO2

125°C, Pressure

OCOONa

Rearrangement

OH

COONa           Dil. HCl

COOH

 

 

Sodium phenoxide

Sodium phenyl carbonate

Sodium salicylate

Salicylic acid

 

 

It is a commercial method. The reaction yields both o- and p- isomers. Salicylic acid is more volatile and separated by steam distillation.

  • Reimer-Tiemann reaction

 

 

4

OH + CCl

+  KOH

Heat

OH COOK

Dil. HCl                                         OH

COOH

 

 

  • From benzene derivatives

 

 

 

(a)

 

 

 

(b)

Cl COOH

o-Chlorobenzoic acid

 

 

SO3K COOH

o-Sulphobenzoic acid

Fuse with

NaOH

 

 

 

 

Fuse with

KOH

OH COOH

 

 

OH COOH

 

 

 

(c)

 

 

 

(d)

 

 

 

(e)

OH          + CH2OH

Salicyl alcohol

 

 

OH         +

CH3

o-Cresol

 

 

NH2 COOH

Anthranilic acid

[O]

 

 

 

[O]

Chromic acid

 

 

 

 

PbO/NaOH

 

 

 

 

 

 

 

NaNO2/HCl

C

OH COOH

 

 

OH COOH

 

 

N2Cl COOH

 

 

 

 

 

 

 

 

 

 

 

 

H2O

heat

 

 

 

 

 

 

 

OH COOH

 

 

 

(2)  Physical properties

  • It is a colourless needle shaped crystalline compound.
  • Its p. is 156°C.
  • It is sparingly soluble in cold water but readily soluble in hot water, alcohol, ether and
  • It is steam
  • It is poisonous in However, its derivative used in medicine internally and externally as antipyretic and antiseptic.

(3)  Chemical properties

  • Reaction with Na2CO3, NaHCO3 or NaOH

O

||

 

 

Salicylic acid

C – OH OH

COO Na+

Aq. Na2CO3                                                         Aq. NaOH

OH

Mono sodium salicylate

COONa

 

ONa

Disodium salicylate

 

  • Reaction with alcohols or phenols

OH

+   CH3OH

 

 

HCl(gas)

OH

+ H2O

 

COOH

Salicylic acid

COOCH3

Methyl salicylate

 

 

Methyl salicylate is an oily liquid (oil of winter green) with pleasant material. It is also used in medicine in the treatment of rheumatic pain and as a remedy for aches, sprains and bruises. It is used in perfumery and as a flavouring. It is used for making of iodex.

 

OH

+    C H OH

OH

POCl3

 

 

 

Salicylic acid

6    5

COOH

COOC6H5

Phenyl salicylate (salol)

 

Salol is a white solid m.pt. 43°C. It is a good internal antiseptic. It is used in making of toothpastes. Salol absorbs ultraviolet light and its main use now is sun-screening agent and stabiliser of plastics.

  • Decarboxylation

COOH

 

D

 

OH

Salicylic acid

OH

Phenol

+    CO2

 

 

 

  • Acetylation

 

Salicylic acid

 

OH COOH

 

+   ClCOCH3

 

Acetyl chloride

 

 

 

Pyridine

 

 

 

 

 

 

Aspirin

 

OCOCH3 COOH

 

(Acetyl salicylic acid)

 

Note : ® Aspirin is a white solid, melting point 135°C. It is used as antipyretic and pain killer (analgesic action).

 

 

 

  • Reaction with ferric chloride solution

OH

 

 

 

 

Salicylic acid

 

  • Reaction with PCl5

COOH

FeCl3

Solution

Violet colouration

 

 

Salicylic acid

 

  • Bromination

OH COOH

Cl

PCl5

COCl

o-Chlorobenzoyl chloride

 

OH

 

 

Salicylic acid

OH COOH

Br2 water

Br                     Br

 

 

Br

 

2,4,6,Tribromophenol

 

 

  • Nitration

 

Salicylic acid

OH COOH

 

 

 

Fuming HNO3

 

O2N

 

 

 

 

NO2

 

NO2

 

2,4,6,Trinitrophenol

 

Phthalic acid [1,2,-Benzene dicarboxylic acid]

COOH

 

COOH

There are three isomer (ortho, meta, para) of benzene dicarboxylic acid.

 

 

COOH                                             COOH

COOH

COOH

 

 

 

 

 

 

Benzene-1,2-dicarboxylic acid (Phthalic acid)

 

(1)  Methods of preparation

COOH

 

Benzene-1,3-dicarboxylic acid (Isophthalic acid)

 

CH3

COOH

Benzene-1,4-dicarboxylic acid (Terphthalic acid)

 

[O]                               CH3

 

 

 

  • COOH

 

  • By the oxidation of o-xylene :

 

o-Xylene

CH3

KMnO4

COOH

o-Toluic acid

COOH

Phthalic acid

 

  • From naphthalene (Industrial method) : It is known as aerial

 

 

 

 

 

 

 

 

Naphthalene

Fuming H2SO4 HgSO4,300°C

CO    O CO

Phthalic anhydride

COONa COONa

COOH COOH

 

 

(2)  Physical properties

  • It is colourless crystalline
  • Its melting point is not sharp (195–213°C).
  • It is sparingly soluble in cold water but soluble in hot water, alcohol, ether, benzene

(3)  Chemical properties

 

 

 

NaOH                                               COONa

COOH

Acid salt

 

C2H5OH                                                           COOC2H5 COOH

Ethyl hydrogen phathalate

COONa COONa

Disodium phthalate

 

2   5

C H OH                                         COOC2H5 COOC2H5

Ethyl phthalate

 

 

 

PCl5                                                                                                  COCl

COCl

Phthaloyl chloride

 

 

 

COOH COOH

Phthalic acid

NH3

COONH4 COONH4

Amm. phthalate

CONH2       

CONH2

Phthalamide

 

 

heat                                CO        O

 

H2O

 

 

 

Soda lime heat

 

 

 

Hg (CH3COO)2

CO

Phthalic anhydride

 

 

 

 

Benzene

 

COO COO

 

 

 

 

 

Hg           heat                                  CO Hg

CO

CO         NH

Phthalimide

 

 

 

 

 

 

O

 

 

 

  • Uses : It is used in the manufacture of plastics, dyes and other compounds such as phthalic anhydride, phthalimide, anthraquinone and fluorescein

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