"Synthesis of Ortho-chlorobenzoic acid from anthranilic acid"

 

Step III: Ortho-chlorobenzoic acid from anthranilic acid.

Chemicals Required:

1. Anthranilic acid
2. Sodium nitrate
3. Conc. HCl
4. CuSO₄ (Crystalline)
5. Sodium Chloride
6. Cu-turnings

Theory:

Diazo coupling:

The reaction in which aryl diazonium or diazocation, ArN⁺, may attack highly activated aromating ring. The electrophile is generated of primary reaction of aromatic amine and HNO₂ by the diago Coupling. A diazocation is unstable so it decomposes to lose N₂. In order to present this decomposition, diazotization is done at temperature (0-5⁰C). Primary or Secondary aromatic amines also react with diazocation yielding N-coupled Product which may be re-arranged to more Stable C-coupled product by heating, with mineral acid.

Sandmeyer Reaction:

The Substitution of amine group via preparation at its diazonium salt with nucleophile (Cl, I, CN, RS, OH) under the catalysis of Copper II.

Chemical reaction:

 

Mechanism:

 

Procedure:

1. I dissolved 20 g CuSO₄ and 8.5 g of NaCl in about 40 ml water taken in 500ml round bottom flask.
2. Then I boiled it and added 55ml of HCl and 10 g of copper turnings into it.
3. I heated the flask under reflux until mixture become Cooled.
4. Then I prepared anthranilic acid solution in HCl and water and cooled it to 0⁰C.
5. After that I added NaNO₂ in it slowly with continuous stirring.
6. Then I pouerd this solution to above prepared solution.
7. After that I allowed the solution to stand for about 4 hours.
8. Then, I filtered the crystals.

Calculations:

Mass of anthranilic acid = 3.2g

Molecular mass of athranilic acid = 137g/mol

Moles of anthranilic acid = m/M = 3.2/137 = 0.02335 moles

From chemical equation

1eq of anthranilic acid = 1eq of orthochlorobenzoic acid

0.02335 moles of anthranilic acid = 0.02335 moles of orthochlorobenzoic acid

So,

Moles of orthochlorobenzoic acid = 0.02335 moles

Molecular mass of orhtochlorobenzoic acid = 156.5g/mol

Mass of orthochlorobenzoic acid = n×M = 0.02335 × 156.5 =3.654g

Theoretical yield = 3.654g

Actual yield         = 2.7g

%age yield of o-chlorobenzoic acid = 2.7÷3.654×100 = 73.89%

 

 %age yield of O-chlorobenzoic acid= 73.89%

 

Melting point:

The melting point of this compound is 141⁰C.